Study Of Microstructure And Abrasion Resistance Of Novel Co-based Alloy Laser Cladding Coatings

A novel cobalt-based alloy powder was cladded on SS316 valve sealing surface to solved valve failure which used high power diode laser to replaced traditional iron-based,nickel-based or cobalt-based alloy valve sealing surface in this paper.The optimized laser cladding parameters were obtained through a lot of experiments.Novel cobalt-based alloy was successfully cladded on valve sealing surface and no cracking found in coating.Wear and abrasion tests also showed good wear and abrasion resistance of novel cobalt-based alloy valve sealing surface.The microstructure and phase compositions were characterized by OM,SEM,XRD and EDS.The microhardness,wear and abrasion properties were examined by microhardness tester,wear test machine and automatic scratch tester respectively.The results showed that the microhardness of novel cobalt-based alloy laser cladding coatings were 3.1 times the substrate and the OM analysis showed that the main grains were cellular grain,dendrite grain and equiaxed grain.The laser cladding coating phases consist of fcc-Co,Co₃Mo,?Co,W?₃C,Cr₇C₃ and Cr₂₃C₆.The reduction of carbon content and intermetallic compounds Co₃Mo formation prevented coating cracking and kept high hardness of 610 HV_0.2.Wear volume loss of novel cobalt-based alloy coatings is similar with the wear volume loss of Stellite 3.Wear mechanism of the coatings are oxides adhesive and carbides brittle abscission.Scratch test of the coatings showed that the work hardening phenomenon was found on the coating surface.The depth and hardness of scratch groove could reach 120?m and 900 HV_0.2 respectively.Scratch depth of novel cobalt-based alloy coating is 50%substrate scratch depth.It showed that new coating has good resistance of plastic deformation and elastic deformation.Secondary phase precipitation prevented grain sliding along the boundary and micro-crack propagation.Scratch mechanism of the coating was plastic removal mode and crack propagation.Ball valve and butterfly valve sealing surfaces were cladded by novel cobalt-based alloy.Valve switch tests were detected under no-load.The results showed that no leakage occurred on ball valve and butterfly valve sealing surfaces under specified duration of 30000 and10000 cycles respectively.It showed that novel cobalt-based alloy can successfully cladded on the valve sealing surfaces and it laid the foundation for future applications.