Effect of tempering treatment on the microstructure and hardness of plasma-clad W6Mo5Cr4V2 high-speed steel clad layer on thrust rings

This study has employed the plasma cladding technique to fabricate the 2-layer W6Mo5Cr4V2 high-speed steel clad layer on the surface of the thrust ring sample made of 42CrMo alloy structure steel. Then, the clad samples are tempered once and twice in the condition of 550℃×1h. Subsequently, the microstructure morphologies, the composition, the elemental distribution, and the hardness of the clad-layer were analyzed in details. The following conclusions were obtained: The plasma-clad W6Mo5Cr4V2 high-speed steel clad layer consist of α-Fe, α'-Fe, platelike carbides W₂C and MoC, strip-shaped carbides Cr₂₃C₆, granular and block-shaped carbides MoC, VC;After tempering, the size and volume fraction of the carbides increase, the structure of grid-like carbides is gradually disappeared, and the particle-reinforced carbides are diffusely precipitated at the same time;The average Rockwell hardness of the untempered W6Mo5Cr4V2 high-speed steel clad layer is 123% higher than that of the 42CrMo alloy structural steel substrate. After first tempering, the hardness increased by 138% to 63.3HRC. After second tempering, the Rockwell hardness of the W6Mo5Cr4V2 high-speed steel clad layer is increased to 64.3HRC, which is 142% higher compared with that of the 42CrMo alloy steel substrate; The W6Mo5Cr4V2 high-speed steel clad layer that has been tempered by 550℃ has a high Rockwell hardness, which is conducive to improving the wear-corrosion resistance of the thrust ring during use. This study has provided potential technical solutions to enhance the lifetime of the thrust rings under extreme wear-corrosion conditions.