Cavitation erosion and erosion-corrosion resistance of austenitic stainless steel by plasma transferred arc welding

Abstract

Abstract 41WC-36Ni7.5CrSiB (Colmonoy75) and NiCrBSiW (Colmonoy88) alloy coatings were synthesized on 316 L stainless steel by plasma transferred arc welding, aiming at improving cavitation erosion and erosion-corrosion resistance. The microstructure, chemical composition, phase constituents and microhardness were determined by using SEM, EDS, XRD and microhardness tester. The cavitation erosion and erosion-corrosion experiments of the coatings were investigated using an ultrasonic vibrator and a jet erosion testing measurement in 3.5 wt% NaCl solution, respectively. Experimental results showed that the coatings with few pores, cracks or other defects could be obtained. The microstructure of the Colmonoy75 and Colmonoy88 coatings exhibited cellular dendrite and irregular blocky phases. The two coatings were composed of γ-Ni solid solution and WC particles, while the formation mechanism of WC was different. In the cavitation erosion and erosion-corrosion tests, the cumulative volume losses of the two coatings were much lower than that of the substrate. Colmonoy88 coating exhibited a better resistance to cavitation erosion and erosion-corrosion than Colmonoy75 coating. The cavitation erosion and erosion-corrosion resistance of the Colmonoy75 coating could reach about 3 times and 8 times that of 316 L substrate, while the Colmonoy88 coating could reach about 12 times and 31 times that of 316 L substrate, respectively. The improvment in the cavitation erosion and erosion-corrosion resistance for Colmonoy88 coating could be attributed to the fact that the in situ synthesized WC particles increased the cavitation erosion and erosion-corrosion resistance by providing an anchoring effect on the solid solutions to hinder the nucleation and propagation of cracks.