Laser surface alloying of AISI 304 stainless steel with WC+Co+NiCr for improving wear resistance

Abstract

The present investigation aims at improving the wear resistance of AISI 304 stainless steel by laser surface alloying of AISI 304 stainless steel with WC+Co+NiCr (in the weight ratio of 20:40:40). Laser surface alloying was carried out by melting the surface using a 5kW continuous wave (CW) Nd:YAG laser at a beam diameter of 4mm, with the output power ranging from 1-3kW and scan speed from 0.005 m/s to 0.1 m/s by simultaneous feeding of precursor powder at a flow rate of 20mg/s using Ar shroud at a gas flow rate of 5 l/min. The effect of laser parameters on the microstructure, composition and phases was studied in detail. Finally, the wear and corrosion behavior of the laser surface alloyed stainless steel was evaluated and compared to that of as-received AISI 304 stainless steel. It was discovered that laser surface alloying leads to formation of a defect free and continuous alloyed zone. The microhardness of the alloyed zone was improved to 250-320 VHN as compared to 232 VHN of as-received substrate. The wear resistance property was improved significantly due to grain refinement and presence of WC,W(sub2)C, CoC as precipitates and Cr, Ni in solution. The optimum parameters for laser processing were derived.