Cast iron is widely used in various industries due to its unique properties. However, the challenges of repairing these components can be daunting because of the welding process. Titanova, a leader in laser cladding, has developed a proprietary technique that enables the repair of the biggest castings.
This article will explore the benefits of cast iron, the challenges involved in repairing it, and how Titanova’s laser cladding technique addresses these issues.
Cast Iron: A Versatile Material
Cast iron is an iron-carbon alloy with a high carbon content of over 2% and silicon between 1-3%. This chemistry allows for lower melting points, which is a main benefit to the industry.
Cast iron has many classes and subclasses, each with unique properties and applications. The following are the several types of cast iron:
Grey cast iron: used in gearbox cases, engine cylinder blocks, flywheels, and machine-tool bases
White cast iron: used in anti-erosion piping and bearing surfaces
Malleable iron: used in axle-bearing retainers, track wheels, and automotive crankshafts
Ductile or nodular iron: used in gears, camshafts, and crankshafts
Ni-hard Type 2: used in high-strength applications
Ni-resist Type: used for resistance to heat and corrosion
Challenges of Repairing Cast Iron
Here are some of the main obstacles to repairing cast iron components:
Cast iron contains a high amount of carbon, typically between 2% and 4%. This carbon content causes the material to become brittle and prone to cracking when exposed to high heat during welding. Welding also causes the carbon to migrate to the weld pool, leading to porosity and weakening the weld joint.
Microscopic Impurities and Inclusions
Cast iron is not a pore-free material; it contains microscopic impurities and inclusions that make it challenging to repair. These inclusions come in various shapes — from flakes to spherical nodules — and can cause stress concentration, leading to cracks and fractures.
Saturation of Lubricants and Other Surface Substances
Cast iron components used in industrial applications are often exposed to various substances. This includes lubricants, greases, and water that can saturate the surface and create a barrier to adhesion during the repair process. This makes it difficult to achieve proper bonding and leads to failure in the repaired area.
Costly and Time-Consuming Preheat Requirements
Repairing cast iron often requires preheating the component to slow down the cooling rate of the weld and the surrounding area. However, preheating large cast iron components can be time-consuming and expensive, often requiring temperatures between 500-1200 °F. Preheating must also be done uniformly, or it can cause the part to crack, making the repair process even more challenging.
Titanova has years of experience and expertise in laser cladding techniques! This has allowed us to develop proprietary methods specifically designed for repairing all types of cast iron components.
Our laser cladding technique uses a laser beam to melt a powder or wire-based coating material. Afterward, it is bonded onto the surface of the cast iron component. This process results in a metallurgically bonded layer highly resistant to wear and corrosion.
Laser cladding offers several benefits over traditional welding techniques for repairing cast iron components. Unlike conventional welding, laser cladding requires minimal preheat, significantly reducing the time and cost associated with repairs. Additionally, the laser cladding process produces a much smaller heat-affected zone, reducing the risk of cracking during the repair process.
Trust Titanova to provide the laser cladding expertise to keep your operations running smoothly!
Contact us today to learn more about our services and how we can help you achieve your material processing goals.
Laser cladding and hard laser facing are welding techniques that provide a protective surface coating on metal parts. Also called laser metal deposition (LMD), laser cladding utilizes a focused laser beam to generate heat, and clad material is simultaneously fed into the resulting melt pool on the targeted surface area of a metal component. The result is a metallurgically bonded protective layer that enhances a component’s resistance to wear and corrosion associated with environmental and chemical factors. This is done with low dilutions and small heat-affected zones.
Such protection is particularly essential for components across the oil and gas industry. Part exposure to salt water, chemicals, oxidation, and temperature extremes takes a toll on metal components and can lead to downtime and productivity losses due to leakage or part failure. Learn more about the applications for laser cladding in this industry, and how it can help safeguard your equipment from corrosive service conditions.
Laser Cladding Applications in the Oil and Gas Industry
The oil, gas, and petrochemical sectors require parts that can withstand rugged applications in harsh environments. Applications for laser cladding in this industry include:
Bearings, bearing bushes, and bearing journals
Cutting and drilling components and tools
Gate and ball seats and valves
Hydraulic cylinders and plungers
Seals and seal seats
Why Laser Cladding?
Due to corrosion problems in the oil and gas industry, its equipment components benefit greatly from a protective coating. Compared to standard additive methods, laser cladding provides a very low dilution corrosion- and erosion-resistant layer that extends part life and improves operational reliability and performance. Using lasers allows for greater precision and lower heat input that minimizes dilution, and distortion and enhances the properties of the metal substrate. As an added advantage, the process yields very thin weld overlays enabling part designers the choice to use generic base metal alloys for their parts.
All these advantages generate time and cost savings, as well. Covering a more affordable substrate with a thin, specialized surface coating can reduce material expenditures. Coated parts better withstand chemical exposure and mechanism wear, which prevents costly downtime and saves on maintenance and repairs. Offering shorter production times than plasma transferred arc (PTA) welding and other traditional techniques, laser cladding ultimately boosts productivity.
Titanova Laser Cladding
For minimal dilution, Titanova, Inc. uses a laser cladding method capable of welding a very smooth and thin single-pass metal layer overtop of a substrate at high rates of deposition. Stainless and tool steels, superalloys, chrome, cobalt, and nickel alloys are just some of the optimal metals for this process. Our technique allows us to successfully modify the surface metal’s chemistry without creating much weld distortion or a large heat-affected zone. With laser cladding, we can generate functional, cost-effective, and customizable components with enhanced resistance to wear, corrosion, oxidation, and high-temperature fatigue.
Founded in 2008, Titanova strives to provide products and services of the highest quality that meet or exceed customers’ expectations for 100% customer satisfaction. As a full-service ISO 9001:2015-certified laser job shop and certified member of ASME, ASM, AWS, and NTMA, we are committed to continual improvement, offering innovative laser processing solutions and supplying the thinnest and purest clads available in today’s weld overlay market.
For more information on our laser cladding services and how they can benefit your operation, contact us today.
While welding is often used to join metals together, it can also be used as a protective technique. Weld overlay, also known as weld cladding, is the process of melting a protective layer of metal atop another metal surface. The application of laser light heats and melts the cladding metal onto the parent metal, creating a welded surface with greater corrosion or wear resistance. In some cases, multiple metals will be alloyed or layered over one another to enhance the surface’s properties even further.
Weld overlay can be further classified based on its function. Corrosion-resistance overlay, as its name suggests, is used with chrome or nickel based metals to protect against oxidation. Hard-facing weld overlay is similar, but it is performed with the aim of increasing wear resistance. These processes offer a cost-effective and economical way to extend the equipment’s working life.
Titanova offers expert laser cladding and hard-facing services that ensure quality results at affordable prices.
Types of Weld Overlay Processes
To create an effective overlay, providers will match both the materials and the welding technique to the project. To do so, they must consider the goal of the overlay, the properties of the parent metal, and the characteristics of the work environment.
Some of the application options include:
Laser Welding. Typically an automated process, laser welding uses a focused beam of light to quickly melt the cladding into the parent metal. Laser offers high efficiency and excellent results with a smaller heat-affected zone than is possible with conventional arc welding.
Shielded Metal Arc Welding (SMAW). Among the most common welding techniques is shielded metal arc welding, which is more affordable than some other options. It is a manual process that requires the use of a flux-coated consumable electrode. An electrical current creates an arc between the electrode and the metal surface, melting it to join the cladding to the parent metal. The flux melts to create its own shielding gas and produce slag, which adds additional protection to the overlay.
Metal Inert Gas (MIG) Welding. MIG welding is like SMAW welding in that it uses a consumable electrode that melts to form an overlay. However, the electrode does not contain flux, so the shielding gas must be added separately.
Tungsten Inert Gas (TIG) Welding. TIG welding is another shielded arc welding technique, like MIG, but it uses a non-consumable electrode. A separate wire is used to add filler material.
Plasma Transferred Arc (PTA) Welding. PTA welding is an inert-gas process that uses a non-consumable electrode like TIG welding. The major difference is that the cladding material is added directly to the arc as a powder.
Submerged Arc Welding. As its name suggests, submerged arc welding is distinct from other processes because the arc stays hidden—or submerged—beneath the flux blanket. In other respects, submerged arc welding closely resembles SMAW.
Laser Weld Overlay Process Benefits
Laser weld overlays offer significant advantages compared to other surface treatments, including other weld overlays. Because it produces the lowest dilution of any overlay technique, laser cladding is highly economical. The lower heat input also decreases the risk of overheating, meaning that it can be used with parts of all sizes, and the resulting heat-affected zone will be very small. Laser cladding also produces smooth, flat cladding free from surface imperfections. Items Laser clad require little to no finishing, further improving the efficiency of the process.
Industries and Applications
Laser cladding is used in any industry where iron-based metals are exposed to environmental conditions like abrasive materials, precipitation, moisture, or corrosive chemicals. For instance, construction, mining, and excavation equipment can often benefit from hard-facing, as can plumbing components.
Industries whose operating conditions make laser cladding a good option include:
Wastewater and water treatment
Materials Often Used for Weld Overlay
Just as important as the choice of welding overlay technique is the choice of material. Not all metals can be welded together—titanium, copper, and aluminum, for instance, are poor candidates for overlays.
Some materials that tolerate cladding well include:
Nickel-based alloys, including Inconel and Hastelloy
Your provider will help you evaluate surface treatment options and determine whether a weld overlay is right for your situation.
Welding, brazing, and soldering are three different processes that join metals. They all use heat to join metal primary differences between welding, brazing, and soldering are the melt temperatures of the metals or materials used in the process and what is being melted. There are many different welding techniques but here we will discuss only thermal techniques. Welding encompasses several different techniques that use energy to melt the base and filler metals together, forming a welded joint. Brazing and soldering molten metal alloy fillers to create a joint between base metals components. The difference is that brazing fuses joints at higher temperatures than soldering, but both typically do not melt the base metal components that are joined
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Welding, brazing, and soldering each have advantages and disadvantages for certain applications. Find out more about their distinct characteristics here.
What Is the Difference Between Welding, Brazing, and Soldering?
Welding, soldering, and brazing are distinct metalworking processes that suit certain applications better than others. Here we’ll explain each process’s features, advantages, and disadvantages.
Welding permanently joins metal parts by melting the surfaced to be joined together and in some cases using filler materials to fill gaps.
Advantages of welding include:
strong joints, sometimes stronger than the base metals
highest strength joint without heating the whole part
process can be done just about anywhere
Disadvantages of welding include:
Limited choice of metals alloy combination
Difficult to impossible to rework
Not compatible with mixed metals i.e copper to steel or aluminum to steel
In some case required pre or post weld heat treatments
Brazing involves heating filler metal to its melting point rather than melting the base metals. The molten filler material covers the joint through capillary action and creates a strong alloy seal. It is higher than soldering thus less sensitive to corroded or dirty surfaces.
Advantages of brazing include:
Filler metals have a lower melting point than the base metal
Joins metals and nonmetals, including copper, bronze, Aluminum, and ceramics
Does not require secondary finishing
Easier than welding to rework
Good for large-scale production
Uniform heating limits thermal distortion
Base metal properties typically remain the same
Disadvantages of brazing are:
Capillary action means metals must be very tightly fit during brazing
Requires flux during brazing and flux residue cleaning afterwards
Compatible base metal size is limited
Filler alloys are a different color than the base metal, making the joint less aesthetically appealing
Weaker than welded joints
Joints deteriorate at high temperatures
Soldering melts the filler metal at a lower temperature, typically less than 450 °C. This is much lower than the base metals melt temperature. The maximum temperature in brazing can go up to 1000 °C, while welding can involve temperatures as high as 3,800 °C. The applications of soldering and brazing are similar, but the relatively low temperatures of soldering mean that it is has the attributes of the least amount of thermal damage and both require tightly fitting joints and fluxes.
Advantages of soldering include:
Requires least amount heat input than welding and brazing
Can join dissimilar base materials together
Compatible with thin-walled parts
Produces little residual stress and thermal warping
Doesn’t require heat treatment after processing
Disadvantages of soldering include:
More surface preparation and Flux required
Joints are not as strong as those produced through welding or brazing
Not effective for load-bearing joints or heavy metals
Unable to fuse large joints
Not suitable for high-temperature applications
Why Use Titanova for Welding and Brazing Services
When choosing from welding vs. brazing vs. soldering, it’s important to understand your unique joining requirements first, including the materials and intended application. Titanova provides cutting-edge welding and brazing services for nearly all types of metal bonding. Lasers are one of the most precise heating methods for these applications. Our team provides laser welding with minimal distortion for defect-free welding. Our laser brazing services are highly precise and reduce part distortion and energy costs. Contact us to learn how we can help you with your next project.
Posted by John Haake on | Comments Off on Thermal Spray vs. Laser cladding
This blog is meant to explain the differences between the thermal spray and laser cladding processes and help you understand the physical differences between each process.
What is Thermal Spray?
Thermal spraying refers to a group of coating processes in which finely divided metallic or nonmetallic materials [ceramics] are deposited in a molten or semi-molten condition to form a coating. The coating material may be in the starting form of powder, ceramic rod, wire, or molten materials.
The basic process is shown in Figure 1.
Figure 1 – Basic Thermal Spray process
Since there are a large number of materials and heating methods, research has resulted in many different commercial application methods. In Figure 2, a schematic segregated by a thermal heat source method is shown. In general, the flame is chemical combustion and the electrical is a plasma arc.
Figure 2 – Thermal spray application methods
As can be seen from Figure 1, the heat source is disconnected from the workpiece and only affects the thermal spray material, therefore the adhesion of the thermal spray coating is mechanical and NOT welded. This naturally results in a very low heat process, which produces no distortion to the workpiece. On a microscopic level, the coatings are porous. Since the adhesion is mechanical, the coating thicknesses are limited to < 0.015” due to inherent internal stresses and are subject to spallation.
Thermal Spray and Fuse of Self-Fluxing Alloy Powders
Since thermally sprayed material is not metallurgical alloy-bonded to the substrate and the coatings are typically porous, the industry developed thermal spray powder chemistries that are self-fluxing. Self-fluxing alloy is the generic name given to the nickel- or cobalt-based thermal spray powders used to hard-face industrial parts subject to severe abrasion or corrosion.
The thermally sprayed workpiece is heated to a temperature that is at the melt temperature of the self-fluxing alloy, which is below the workpiece melt temperature. As can be seen, the self-fluxing process produces an alloy [welded] bond and eliminates porosity, and achieves thicker and harder coatings. Since the entire workpiece must be heated to a temperature of around 2000° F, this process is typically limited to minor distortion insensitive cylindrical parts.
What is Laser Cladding?
Laser Cladding, also known as laser weld overlay, laser additive manufacturing, direct laser deposition [DLD], and laser spray welding, is a welding process analogous to electrical arc welding processes such as GTAW, TIG, MIG, and PTA in which the heat source is co-located where the overlay material and the workpiece surface come in contact. The heat source is energetic enough to melt the coating material and a portion of the substrate to create a welded bond. Melting as little of the workpiece substrate as possible is beneficial with respect to distortion, intermetallic dilution, and structural defects.
The laser is the heat source, and the physical attributes of the laser are immediately recognizable when it comes to weld overlays. Lasers generate controllable optical energy that can be used to controllably modify materials. The lasers are controllable in terms of direction and beam shape. This process involves surface-only optical heating since the energy is pure radiation energy in the form of photons. This results in instantaneous heating, which enables instantaneous control. As previously mentioned, this process can create a weld overly with the smallest amount of heat input, resulting in the lowest amount of distortion, intermetallic dilution, and almost zero defects.
Benefits of Laser Cladding
The inherent benefits of laser cladding are:
Much less weld distortion = Less post-machining
Low dilution =
Less solidification cracking,
Less hard cracking
Meeting single pass chemical specifications
Less preheat = Less tempering
Thinner clad = Lower material costs and pre-machining costs
Smoother clad = Less post-machining
CONTACT THE LASER WELDING EXPERTS AT TITANOVA TODAY
If you’re looking for laser cladding, thermal spray, or other laser material processing services, consider Titanova. We have over 30 years of experience in the area. For information about our laser cladding capabilities, visit our laser cladding capabilities page or contact us today.
Posted by John Haake on | Comments Off on Introduction to the Laser Cladding Process
Laser cladding—also referred to as laser metal deposition or Laser weld overlay—is a manufacturing technique used to add metal material to the surface of a component. It is generally used to create a protective coating that increases the functionality of the part or product. However, it can also be used to repair worn or damaged surfaces.
The following blog post provides an overview of the laser cladding process, outlining how it works, typical applications, materials used, and key advantages.
How Does the Laser Cladding Process Work?
As suggested by the name, the laser cladding process involves the use of a laser. The laser scans across the surface of the workpiece, creating melt pools in targeted areas. At the same time, a stream of metallic powder or wire is introduced to the targeted areas, which allows the laser to melt the material. The short exposure time reduces the amount of heat and therefore the heat affected zone and enables the workpiece and coating material to cool quickly. The result is a metallurgically bonded coating layer that is tougher than one created using the thermal spray coating method and safer to create than one made through the hard chromium plating method.
Applications of the Laser Cladding Process
Since the laser cladding process can add protective coatings and restore worn/damaged surfaces, it finds use in many industries. For example:
In the construction industry, it is used to coat various machines and systems to protect them against corrosion, impact, and wear. The created coatings help extend the service life of the equipment, reducing repair and replacement costs for construction companies.
In the oil and gas industry, it is used to coat cutting and drilling tools. These components are regularly subjected to stresses that can reduce their service life without proper wear protection. The laser clad process increases the surface durability of the tooling, allowing it to withstand long-term use.
In the mining industry, it is used to coat hydraulic cylinders. The coatings on hydraulic cylinders are highly susceptible to corrosion in mining facilities, which can lead to leaks. Coatings created through the laser cladding process are longer-lasting than ones made through the chrome plating process, which can lead to significant cost savings over the years.
What Materials Can Be Used With the Laser Cladding Process?
The laser cladding process can be performed with a broad selection of metals, including, but not limited to, the following:
Nickel (self-fluxing) alloys
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Advantages of Laser Cladding
There are many advantages to using laser cladding over other coating methods. For example:
It allows for the precision positioning of coating materials, enabling coaters to target specific areas on the component.
It creates layers that are more impact resistant than ones made through the thermal spray coating method, which can lead to better protection for components.
It produces layers with little to no porosity, which creates denser (>99.9% density) coatings.
It requires relatively low heat input, generating a narrower heat-affected zone (HAZ).
It generates minimal distortion in the workpiece, reducing the need for post-coating processing.
It accommodates the use of laser power modulation technology, which allows for better thermal control.
Learn More About Laser Cladding From Titanova
Want to learn more about the laser cladding process? Ask the experts at Titanova! We have extensive experience providing laser processing solutions, including laser cladding, to customers across a wide range of industries. Our team can answer any questions and address any concerns you may have about the process.
Do you require a laser cladding partner for your next project? We are here to help! Equipped with customized diode lasers, we can create the thinnest and purest weld overlay possible. Check out our laser cladding service page to learn more about our capabilities.
Posted by John Haake on | Comments Off on Hardfacing Methods
Hardfacing delivers a wear-resistant and hard coating of material on the surface of a worn component or a new component that will be subject to wear. There are various methods that can be used to apply the hardfacing layer. Common methods include:
Diode Laser Hardfacing
The different hardfacing techniques provide different results to suit a range of applications. This blog will describe the various hardfacing methods to help you determine the ideal method for your application or industry.
Laser WC Hardfacing Mixing Plow
Types of Hardfacing Methods
There are various methods for hardfacing, which include:
Diode Laser Hardfacing
Diode laser hardfacing can increase lifespan and reduce wear of material handling components. The coating is extremely wear-resistant, relying on a laser to weld a thin metal layer embedded with super hard particles. Diode laser hardfacing produces a thin, smooth, and uniform coating. It provides a hard particle density of up to 75% and prevents burning carbides with low heat application.
Submerged Arc Welding (SAW)
SAW relies on flux to unite slag and protective gases into the weld pool. When welding, an arc forms between the flux and the workpiece surface through a continuously fed wire electrode. SAW provides excellent deposition rates, deep penetrating welds, and versatility to perform indoors and outdoors. The leftover flux can also be recycled using a flux recovery system.
Flux Cored Arc Welding (FCAW)
FCAW uses a continuously fed tubular flux-filled electrode and requires constant voltage. It is not ideal for all metals but provides excellent penetration and a high deposition rate. FCAW is suitable for any welding position and allows for manual, automatic, and semi-automatic operations. It is ideal for construction applications due to its mobility and speed.
Shielded Metal Arc Welding (SMAW)
This manual arc welding process relies on a covered flux consumable metal electrode that shields the weld pool. It forms an arc between the electrode and the metal substrate using an electric current. When laying the weld, the flux coating disintegrates and creates a layer of slag and shielding gas to protect the weld while cooling. SMAW has lower deposition rates than other welding techniques but works with a range of metals and alloys. It also allows for diesel or gas power, making it highly portable and suitable for remote regions.
Gas Metal Arc Welding (GMAW)
GMAW or MIG welding relies on a welding gun with a consumable wire electrode and a shielding gas. The process is automatic or semi-automatic and typically uses a constant voltage. While it is unusable for overhead and vertical welds, it requires little cleaning post-weld thanks to its low slag generation and provides high deposition rates with low consumable costs.
Gas Tungsten Arc Welding (GTAW)
GTAW or TIG welding creates an arc between the workpiece and a non-consumable electrode, and an inert gas barrier is formed to protect the welding pool. It has lower deposition rates than other methods but leaves a clean finish without producing slag. GTAW also offers a high range of flexibility, allowing welding to be manually or automatically performed in any position and with a wide range of metals.
Thermal spraying is a hardcoating method that sprays heated or melted materials onto a surface. It relies on chemical or electrical heating to spread a coating up to several millimeters thick over a large area with a higher deposition rate than other methods. Thermal spraying works with various material surfaces and does not heat the surface significantly, making it suitable for coating flammable materials.
Oxygen-acetylene hardfacing is a relatively simple method for those familiar with welding. It is not ideal for coating large components, but it provides low weld deposit dilution and provides enhanced control of the deposit shape. Oxygen-acetylene also delivers lower thermal shock with a slower heating and cooling process.
Metal Compatibility With Hardfacing
Various metals are compatible with hardfacing. The primary requirement for a prospective material to be compatible with hardfacing is a carbon content lower than 1%. Low-alloy steels and carbon steels are typically compatible, but high-carbon alloys may require a special buffer layer.
The following metals offer compatibility with hardfacing:
Cast Iron and Steel
Partner With Titanova for Your Laser Hardfacing Needs
Industrial hardfacing can be applied to various materials using diode lasers, thermal spray, and several welding methods. Each method provides unique benefits and can reliably apply a hardfacing coating on a range of metals. Learn more about Titanova’s laser hardfacing capabilities and contact us to speak with a representative today.
Posted by John Haake on | Comments Off on An Introduction to Laser Welding for Dissimilar Metals
Many industries and applications require dissimilar materials to be joined for chemical, structural, and economic reasons. Combining dissimilar metals in a Weldment or for a weld overlay allow the use of the best properties of each metal. All industries benefit for this and is a primary importance when the overlay [cladding] is used in industrial process involving high temperatures and pressure, thermal cycling, and dynamic corrosive environments.
Before any welding operation can begin, the welder must identify the unique characteristics of each material (Chemistry, melting point, thermal expansion, etc.) and choose the welding method that suits them. When welding different metals together, this typically requires expert knowledge and skills. The right welding method wielded by an experienced welding provider can make it possible to join even the most difficult-to-weld materials.
What Is Dissimilar Metal Welding?
Dissimilar welding refers to welding processes that join different metal alloys. This short article will briefly compare fusion arc welding with laser cladding or laser weld overlay welding.
Can Dissimilar Metals Be Welded?
It is possible to weld dissimilar metals. However, there are many factors that must be considered to ensure the formation of a joint with adequate strength for the intended application. For these reasons, it is essential to partner with a laser welding provider that has experience welding dissimilar metals so you can know you can trust them to address all of the factors appropriately.
Key Factors for Dissimilar Metal Welding Operations
Some of the key factors to keep in mind for dissimilar metal welding operations include:
Dilution and Alloying: During welding of dissimilar metals, the metals will have to have a solid solution in which the mixture will produce stable metallurgical phases. These can be 1 or more phases. The phase is determined by the amount of dilution.
Weldability level: When dissimilar metals are joined, excess dilution can lead to a high risk of Hot cracking also know as solidification cracking. Weldability measures the capacity of one metal to be joined to another without such cracking.
Electrochemical characteristics: During dissimilar metal welding operations, there is a risk of corrosion developing at the part of the joint where the metals transition from one to the other (i.e., the intermetallic zone) or the overlay surface itself. If the metals have significantly different electrochemical properties due to dilution, the corrosion risk is high.
Melting point: Different metals may melt at different temperatures. So welders need to use a welding process [Pre Heating] that quickly brings all metals to their melting points or a welding process that doesn’t require any of them to melt.
Coefficient of thermal expansion: Metals Expand upon heating and therefore change their shape and size when they are heated. If two metals being welded change shape at different rates or to different degrees, it can strain the weld as it sets resulting in thermal cracking.
Heat affected Zone: heat affected zones immediately next to the weld can have significantly different physical properties than the original base metal. For high carbon or cast iron this primarily higher hardness. This can lead to reduced toughness and brittle fracture.
Arc Versus Laser Welding to Join Dissimilar Metals
Millions of man hours and years of research have been dedicated in developing weld procedures for fusion ARC welding corrosion resistance alloy and then joining together these dissimilar components to prevent degradation of strength, toughness, and corrosion resistance.
This traditional welding method most used for joining dissimilar metals is fusion ARC welding. It encompasses traditional welding processes, such as tungsten inert gas (TIG) welding (i.e., gas tungsten arc welding or GTAW) and metal inert gas (MIG) welding (i.e., gas metal arc welding or GMAW).
For laser cladding or laser weld overlay, the physical attributes of lasers, when used as welding heat source, are such that the negative effects of the key factors described above are significantly reduced in their influence. These factors are the primary driver for developing the welding essential variables for a welding procedure qualification. The essential welding process variables are significantly reduced in number and in some cases eliminated entirely.
The laser Cladding of dissimilar materials benefits are:
Laser weld overlay is not as sensitive to different melt temperatures.
Very low dilution
Allows for much thinner clads.
Reduces sensitivity to thermal expansion issues.
Allows for control of detrimental metallurgical phases.
Reduces or eliminates of solidification cracking [Hot cracking]
high corrosion resistance can be achieved in a single thin layer.
Elimination of multiple layer requirement to attain necessary chemistry.
Small heat affected zone = less distortion
Allows overlay onto high hardenability materials without preheat.
preheat requirements significantly reduced are eliminated.
Laser can overlay ductile cast iron without significant preheat.
Post weld heat treatment significantly reduce are eliminated.
Laser as the heat source is the ultimate tool for welding/cladding dissimilar materials.
What Metals Cannot Be Welded?
Material compatibility and incompatibility depend on the welding method used. For example, the fusion welding method cannot be used for the following metal combinations:
Aluminum and carbon steel
Aluminum and copper
Aluminum and stainless steel
Titanium and steel
In these cases, the alternative method to fusion joining is non-fusion welding. It encompasses processes such as diffusion bonding, explosion welding, ultrasonic, and friction welding. They are suitable for joining the above metal combinations and other insoluble metals.
Learn More About Laser Welding for Dissimilar Metals From Titanova
Want additional information on laser welding for dissimilar metals? Ask the experts at Titanova! Equipped with extensive experience providing laser processing solutions, including laser welding and cladding, to customers across a wide range of industries, we can answer or address any questions or concerns you may have about the process.
Does your next project involve laser welding or cladding? Partner with us today! We also provide autogenous laser welding capabilities for a variety of metal parts and products. Visit our laser welding page to find out more about our service offerings.
Posted by John Haake on | Comments Off on An Introduction to Autogenous Welding
Welding is a manufacturing process used to join two or more individual pieces. It can be broadly categorized into two classifications: fusion welding and solid-state welding. Fusion welding encompasses all of the processes that utilize direct heat applied from an external source to fuse or melt contact surfaces of metals to weld them together, while solid-state welding encompasses all of the processes that require external pressure to weld materials together.
Fusion welding processes can be further classified by method. There are three main fusion welding methods: autogenous welding, homogeneous welding, and heterogeneous welding. They differ with regard to the application and nature of filler material (i.e., whether or not filter material is used and, if filler material is used, what it is made from). The following blog post focuses on autogenous welding. It highlights how it compares to the homogeneous welding and heterogeneous welding methods, what types of welding processes use it, and what advantages it offers.
Autogenous vs. Homogeneous vs. Heterogeneous Welding
Autogenous welding is a fusion welding method that does not require the application of filler material to form a weld. Since solid-state welding processes generally do not use filler materials, they may also be classified as autogenous.
In contrast to autogenous welding, both homogeneous welding and heterogeneous welding require the application of filler material to form a weld. Welding operations that use the homogeneous welding method need filler material that has the same composition as the base material, while welding operations that use the heterogeneous welding method need filler material that has a different composition than the base material.
Types of Autogenous Welding Processes
Autogenous welding is a method of performing fusion welding processes rather than a specific fusion welding process. Some of the fusion welding processes that use it include:
Laser beam welding. This welding process uses a concentrated laser beam to melt the material and form the desired weld.
Gas tungsten arc welding. This welding process uses a non-consumable electrode to form an high temperature arc to form the desired weld.
Electron beam welding. This welding process uses a high-energy electron beam to form the desired weld.
Plasma arc welding. This welding process uses an ionized plasma arc to form the desired weld.
Advantages of Autogenous Welding
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Compared to the other two fusion welding methods, autogenous welding offers a number of advantages, such as:
Better looking welds. Autogenous welding processes are less likely to create inconsistent or uneven weld bead patterns.
Lesser post-grinding requirements. Since material is not added during autogenous welding operations, welded components do not have excess material that needs to be removed.
Lower material costs. Since autogenous welding operations do not need filler, they have lower material costs.
Greater suitability for thin materials. Autogenous welding is suitable for welding thin sheets since it makes controlling heat, weld bead profile, and arc start/stop easy.
While the above characteristics make autogenous welding ideal for many applications, the method is not suitable for all welding applications. For example, it is not appropriate for welding projects involving/requiring:
High-strength reinforced joints
Plates over 2–3 mm in thickness and requiring full penetration
Edge preparation for filler material
Partner With Titanova for Your Autogenous Welding Needs Today
Need an autogenous welding partner for your next project? Titanova has got you covered! We provide autogenous laser welding capabilities for a variety of metal parts and products. Contact us today to request a quote.
Posted by John Haake on | Comments Off on Guide to Laser Welding
What Is Laser Welding?
To understand laser welding we must step back and generally describe what welding is. Welding is joining similar materials of different shapes and similar melt temperatures. These materials are typically the same material. The welding process concentrates heat at the interface to melt the edges and upon solidification creates a structurally sound joint thus creating a new shape. These materials can be any material from plastics to metals. Welding is distinct from other joining methods that use lower melt temperature material added to the joints of high melt temperature shapes such as soldering and brazing. Welding is a relatively recent human invention that started at the beginning of the 20th century with the invention and access to refined fuels, pressurized gases, and electricity.
LASER (Light Amplification by Stimulated Emission of Radiation) welding is a manufacturing process that utilizes a concentrated beam of photons (light) to join metal or thermoplastic materials (laser plastic welding). Because laser energy is pure energy (photons) that can be focused, it is much better in concentrating heat at the weld joint. This concentration of light allows for a highly efficient process. The efficiency comes from the fact that less heat (energy) is needed to make the weld.
It can be used to form welds on thin materials at high speeds as well as narrow and deep butt welds between square-edged components on thick materials. In both cases, it is highly efficient, requiring only a portion of the heat needed as compared to more traditional welding methods.
Lasers have been around since the 1960s and industry has been using laser in production for welding since the 1970s however these lasers were vacuum tube-based giants that required huge amounts of electrical power. With the advent of super-efficient and small semiconductor lasers in the 1980s the ability to produce and control laser light was the revolutionary equivalent of transitioning from vacuum tubes to transistors. At end of the 20th century the founder of Titanova, John Haake, previously co-founded Nuvonyx, Inc, which was the first company in the USA to sell multi-kilowatt industrial semiconductor (ISL) lasers. These lasers are better known as diode lasers. These diode lasers produce a wavelength of light which are absorbed much more efficiently in all metals to produce heat to weld. This along with the diode system efficiency generates a 50X to 100X improvement in overall weld efficiency. This along with the inherent ability to precisely control the laser energy, both spatially and temporally, has led to a revolution in laser welding technology. These inherent qualities make lasers the go to technology for the manufacturing of a variety of parts and products.
How Does Laser Welding Work?
Diode lasers produce concentrated light that is directed through lenses, mirrors, and fiber optics. This light is transmitted thru welding optics to the weld joint. The light is absorbed by the workpiece material and in this case metal. The metal instantaneously heats up and the intensity (Watts over a surface area – W/Cm2) of the light determines if the metal melts. The size, shape, scan speed, or the laser energy density all are essential variables is determining the weld puddle size and depth. As with all welding processes the material properties, cleanliness, inert cover gas, weld position, etc., are all factors determining the quality of the weld. Because of rapid heating and high speeds, all laser welding is fully automated and typically robotically implemented.
There are a large variety of laser welding processes. They can be separated into two primary classes: autogenous and non-autogenous. In autogenous welding, all molten material originates or is derived from workpiece i.e., no filler material. Non-autogenous is where a filler metal is introduced simultaneously into the laser beam. This filler material can come in a variety of forms but in general it is either wire or powder. There is a further differentiation of the autogenous laser welding and that is conduction mode and keyhole mode laser welding. There are many process conditions that will determine if one is in conduction mode or keyhole mode, but the main attribute is laser intensity (W/cm2).
Types of Autogenous Laser Welding
There are two main types of autogenous laser welding: conduction mode and keyhole welding. They are differentiated based on the laser power density/intensity at a given scan speed across the workpiece.
Heat Conduction Welding
Heat conduction welding is typically used for operations where the power density is less than 100,000 W/cm2. It utilizes low-power densities laser beam sizes which are intense enough to heat metals to above their melting points but not to their boiling point. This boiling or vaporization of the metal is the cause of a keyhole.
As the laser beams are absorbed at the surface of the workpiece rather than penetrating it, the welds formed generally have a high width-to-depth ratio. While the welds are smooth and aesthetic, they are easier to achieve with poor fit up weld joints. The gap to thickness requirement are typically 3X to 5X more forgiving than keyhole welding but not as forgiving a traditional welding process. Thus, conduction mode laser welding is the process of choice for welding thin gauge materials.
Keyhole welding is used for operations requiring deep weld penetrations at the lowest possible heat. The power densities are between >106–107 W/cm2, which translates to spot sizes of less than 0.010” (250 microns) in diameter. At this point, the highly focused laser beam melts and vaporizes the material in the targeted area. It penetrates the workpiece, forming a cavity known as a keyhole. The keyhole is caused by with the recoil forces from the vaporization of the metal. As the laser beam welds the joint surface tension, the molten material at the leading edge of the keyhole flows to the back, where it closes the hole cools and solidifies to form the weld.
The welds formed have a high depth-to-width ratio. This quality and the small size of the laser beam subsequently requires much tighter fit ups. The gap to material thickness requirement typically required press fit parts, and very precise mechanical control.
Laser welding has a variety of unique advantages over traditional welding processes, such as:
Higher accuracy and precision. Laser welding offers a high degree of accuracy and precision. These qualities make it possible to weld even the smallest parts together without causing damage or excessive thermal distortion to them.
Better consistency. Laser welding allows for the creation of consistent and repeatable welds, which helps improve manufacturing efficiency by reducing scrap rates.
Lower risk of distortion. Laser welding technology is a contact-free joining process that uses low levels of heat, which minimizes the potential for thermal and mechanical distortion.
Greater weld speeds. Laser welding is a much faster process enabling greater production throughput.
Broader welding capabilities. The laser welding process can accommodate multiple weld joint configuration. From autogenous to non-autogenous. From thin to thick gauge materials. It also can accommodate dissimilar welding materials, galvanized metals, and even magnetized materials.
Laser Welding vs. Traditional Welding
Welding is an umbrella term for the fabrication processes that utilize heat to join two or more separate components together. It encompasses a variety of processing, including traditional welding methods (e.g., TIG welding, MIG welding, and spot welding) and newer welding methods (e.g., laser welding.)
While the popularity of newer welding methods is spreading, traditional welding methods still remain in use. Each variation offers unique advantages and disadvantages that make them suitable for different manufacturing operations. For example:
Traditional welding methods, such as tungsten inert gas (TIG), metal inert gas (MIG), and spot welding, have long been used by the manufacturing community. As a result, they are well understood. Additionally, they accommodate less precise and accurate workpieces, come with lower initial investment costs, and readily support both manual and automated operations.
Newer welding methods, such as laser welding, benefit from recent technological advancements. Laser welding allows for a smaller heat affected zone (HAZ), lower risk of macro deflections and distortions, faster processing times, and greater suitability for thin metals.
At Titanova, we provide a broad selection of non-cutting laser services to customers in a wide range of commercial industries. One of our core service offerings is laser welding. We offer primarily conduction-mode autogenous welding, but we do provide wire feed non-autogenous welding.
Contact the Experts at Titanova for Your Laser Welding Needs
While traditional welding processes are still common in the manufacturing industry, manufacturing professionals are increasingly incorporating laser welding into their daily operations. The process’s superior accuracy, precision, versatility, and efficiency, making it ideal for the manufacture of many parts and products. That’s why the experts at Titanova use it!