Effects of Laser Scanning Speed on Microstructure and Wear Properties of M2 High Speed Steel Coatings

M2 high-speed steel coatings with laser scanning speeds of 10 mm/s, 12 mm/s, 14 mm/s and 16 mm/s were successfully fabricated by laser cladding. The effects and mechanism of different scanning speeds on the phase composition, microstructure, microhardness and friction and wear properties of M2 coatings were analyzed and studied. The results show that no cracks appear in the coatings under different scanning speeds, and the microstructures of the coatings are mainly composed of columnar crystals, cellular crystals and equiaxed crystals at different scanning speeds. As the laser scanning speed increases, the coating grains are refined. The grain size of the laser coating of about 5 μm is much smaller than that obtained by conventional methods (about 100 μm).With the increase of the laser scanning speed, the carbide content in the coating first increases and then decreases, and the microhardness of the coating first increases and then decreases. When the laser scanning speed is 14 mm/s, the maximum microhardness is 787.07 HV0.2, higher than traditional cast high-speed steel(580-620 HV0.2). With the increase of the scanning speed, the wear rate of the coating decreases first and then increases.When the laser scanning speed is 14 mm/s, the lowest wear rate of the coating is 0.203×10^-3 mg/m.