Cladding hardfacing materials can be achieved using either high-power industrial lasers or low heat input Gas Metal Arc Welding (GMAW)-based Wire Arc Additive Manufacturing (WAAM) processes, such as Panasonic’s Super Active Wire Process (SAWP), Fronius’s Cold Metal Transfer (CMT), and Miller’s Regulated Metal Deposition (RMD).
Laser cladding is a surface coating technique that offers several advantages. It provides excellent metallurgical bonding between the coating and the substrate while maintaining minimal dilution (mixing) with the fully dense deposited material. Its high precision and low distortion minimize machining time after cladding. However, advancements in technology now allow these benefits to be achieved using low heat input GMAW-based WAAM processes (as shown in Figure 1). The mentioned GMAW processes have been investigated and compared at RAMLAB, with some results already published.
A bottleneck of laser cladding hardfacing materials is the high cooling rate, which increases the tendency for cracking. This issue can be mitigated by preheating the substrate, but this introduces an energy-intensive step that does not align with sustainable development goals aimed at reducing carbon emissions. Not only does this increase manufacturing costs, but it is also unsustainable in terms of energy consumption.
While the high cooling rate of laser cladding can result in finer grains that provide higher hardness and strength in the coating material, it also induces much higher residual stresses (500–600 MPa) compared to coatings deposited using low heat input GMAW-based WAAM (250–300 MPa), even when produced at similar heat input levels. This is because the laser (e.g., a Nd:YAG laser) utilizes only about 50% of the heat input effectively, whereas GMAW-based WAAM uses approximately 80%.
During the deposition process, the arc in GMAW-based WAAM can preheat a larger area in front of the melt pool than the laser process. In contrast, laser energy is confined within the laser spot, resulting in sharp thermal gradients that can be unfavorable for processing hardfacing materials. Due to the higher cracking sensitivity during laser cladding of the hardfacing material, it is often necessary to reduce the thickness of the clad layer (typically around 1–2 mm without cracking), requiring the deposition of multiple layers when a thicker coating is needed. In contrast, 2–5 mm thickness single-layer of hardfacing material of can be deposited using low heat input GMAW-based WAAM.
Depending on the application, requirements, and production costs, industries can select the appropriate technique for their needs. At RAMLAB, we have the in-house expertise to provide our customers with the right technology solutions tailored to their specific requirements.
