Effect of Laser Scanning Speed on the Wear Behavior of Nano-SiC-Modified Fe/WC Composite Coatings by Laser Remelting

A supersonic plasma sprayed nano-SiC-modified WC/Fe metal-cermet composite coating was remelted with a fibre-pulsed laser at four different laser scanning speeds (100, 150, 200 and 250 mm center dot min(-1)) while the other parameters were kept constant. The microstructures, microhardness, and tribological properties of the coatings were analysed by means of SEM (scanning electron microscopy), XRD (X-ray diffractometer), and a friction tester, respectively. The results show that, when the laser scanning speed is 100 mm center dot min(-1), the remelted coating is most dense with regard to the coverage of the substrate. The coating with nano-particles became more smooth, and elements Si and C in the nano-particles reacted with Fe, Ni, or Cr and formed a hard mesophase that enhanced the strength and hardness of the coating. With the increase of laser scanning speed, the hardness of the four coatings increased first and then decreased, and the nano-SiC-modified remelted coating showed a maximum microhardness of about HV(0.5)1350, and the nano-particles made the coating's micro-structure finer, at a laser scanning speed of 150 mm center dot min(-1). The friction coefficient and wear rate of the four coatings were 0.58 and 12.01 x 10(-5) mm(3)/(N center dot m), 0.21 and 8.50 x 10(-5) mm(3)/(N center dot m), 0.62 and 20.04 x 10(-5) mm(3)/(N center dot m), and 1.23 and 25.13 x 10(-5) mm(3)/(N center dot m). The remelted coating at a laser scanning speed of 150 mm center dot min(-1) exhibits the best wear resistance and its wear mechanism is governed by slight adhesion wear and plastic deformation.