Laser clad WC reinforced Ni-based intermetallic-matrix composites to improve cavitation erosion resistance

Nickel aluminide intermetallic coatings (IC) and nickel aluminide intermetallic matrix composite (IMC) coatings with a WC particulate reinforcement were successfully clad onto AISI 420 Martensitic stainless steel using a 4 kW Nd:yttrium-aluminum-garnet laser with rotary-disk powder feeding of Ni/Al powder and a Ni/Al+WC powder mixture, respectively. Under optimized processing with pre- and postheat treatment conditions, the nickel aluminide clad layers were free of cracks and pores. The microstructure of the IMC was mainly composed of reprecipitated and refined WC particles dispersed uniformly throughout the Ni-Al matrix with a few partially dissolved and undissolved WC particles. The average hardness of the IC was increased from 330 HV0.2 to 420 HV0.2 by the WC reinforcement. The normalized cavitation erosion resistance (R-e(n)) of the IC and IMC were about 5.2 and 284 times that of the stainless steel substrate, respectively. The superior cavitation erosion resistance of the laser clad layers were explained in terms of microstructure, microhardness and work hardenability. (c) 2006 Laser Institute of America.