Laser Cladding is a directed energy deposition (DED) technology. It is also called laser overlay welding and, when used for additive manufacturing, laser metal deposition (LMD) or Directed Laser Metal Deposition (DLMD). These are many names for essentially the same technology principle: A laser melts and bonds metal alloy layers to a substrate component or a previously deposited layer. The laser cladding layer is entirely dense and metallurgical-bonded with minimal dilution from the underlying metal material. The heat input is minimal, and the added material is applied precisely and selectively. Therefore, laser cladding is a high-quality weld overlay.
Why is laser cladding an important manufacturing technology today?
Laser Cladding enhances the performance of industrial products by generating protective layers against wear and corrosion. It helps save natural resources as engineers have the option of designing parts with generic base metal alloys. A high alloyed material is then locally laser cladded onto the component to generate the desired performance characteristics.
Laser Cladding is also a technology used for restoring and remanufacturing high-value components into the original geometry. In addition to simply repairing the shape of a part, service life and performance improve by selecting an additive material with better wear characteristics than the original component.
Is laser cladding expensive?
Laser Cladding was first developed more than 30 years ago by companies such as Toyota for automotive valve seat cladding, GE for jet engine turbine blades, and Caterpillar for earth-moving equipment, to name a few. Until the 2000s, laser cladding was often considered a "last-resort" technology. This perception was mainly due to the high investment and operating costs of the laser machines. The advancements in modern solid-state lasers, which are much more efficient and enable robotic integration through fiber-coupled beam delivery, have reduced cost significantly and created a paradigm shift for laser cladding. Today the cost-benefit consideration favors laser cladding, and the application spectrum is growing exponentially across many industry sectors.
What are the main characteristics of laser cladding, and how does the process compare to HVOF spraying and PTA welding?
The best-known characteristics of the technology are its great precision and low heat impact. Consequently, there is only minimal or even no effect on the geometrical features of the part adjacent to the laser cladding. Secondary finishing work is less compared to other weld overlay techniques. The targeted characteristics of the overlay can typically be achieved with just one layer, while the higher dilution of other processes requires two or more layers.
In comparison, HVOF or high-velocity-oxygen-fuel spraying is a process that produces a thin coating with a mechanical bond to the substrate over a relatively large area. This cladding layer contains a degree of voids and micro-cracks. It is often cheaper to apply but does not provide the same bond and bend strength as the laser coating.
PTA overlay welding is similar to laser cladding. The main distinguishing characteristic is that a plasma flame melts the substrate and additive material instead of the more energy-dense laser beam. Therefore, the heating and cooling times are slower, and the total heat input is higher when compared to laser cladding. This heat input causes the weld to penetrate deeper into the substrate and dilute the cladding layer.
While all three technologies are essential in modern manufacturing, laser cladding is rapidly growing in popularity for critical components. Its superior cladding layer characteristics and the reduced work for secondary finishing processes make it a cost-effective choice for many high-profile industrial applications.
What are recent innovations in laser cladding?
Recent innovations in laser cladding focus mainly on increasing the productivity of the process while maintaining most of the core characteristics:
- Hot-wire laser cladding introduces a pre-heated wire into the process. Therefore, more laser energy is available to meld the base material with an increased feed rate.
- High-Speed laser cladding (EHLA) melts the additive powder entirely in the laser beam before reaching the base material. The molten powder fuses to the solid base material through heat conduction transfer.
- "Large spot" laser cladding is a process that increases the size of the laser spot on the workpiece to allow for the use of more laser power without melting the base material excessively and increasing dilution.
- Laser cladding with a co-axial laser beam feeds the additive material (typically wire) perpendicular to the workpiece. The laser is projected coaxially around the wire. With this approach, consistent processing conditions exist independent of the direction of travel. The development of this technology is primarily focusing on 3d laser metal deposition.
What are typical laser cladding metal alloys?
Laser cladding has a wide range of metal alloys that are suited for the technology. Popular laser cladding alloys include nickel-and cobalt-based superalloys such as Inconel 625, Inconel, Stellite 6, Stellite 21, or stainless steels such as SS316 or SS17-4. It is also possible to conduct laser re-conditioning with the same or similar alloy as the original material.
How is quality checked and maintained during laser cladding?
The laser cladding process has several critical input parameters. Of particular importance are the base material, powder or wire metal alloys preparation, and laser/machine settings. Our welding engineers and Certified Weld Inspectors prepare a Weld Procedure Specification (WPS) for review by the customer that captures the critical parameters for set-up and laser cladding to ensure a high-quality and repeatable process. The WPS is qualified either per LWS or ASME Section IX standards. In addition, we offer reviews and qualifications by external auditing companies such as Det Norsk Veritas (DNV), American Petroleum Institute (API), and others.
Laser Welding Solution utilizes several in-process control and monitoring systems that ensure the highest-quality laser cladding process.
Summary
Laser cladding is an example of a modern manufacturing technology emerging today as we strive to save natural resources and lower life-cycle costs. The process helps reduce cost by allowing engineers to only use expensive high alloy materials in select geometries of a component. Many companies are also selecting laser technology today to re-condition OEM industrial parts and at the same time improve wear- and corrosion-critical characteristics.