Study On Microstructure And Mechanical Properties Of The Co-Cr-Mo Alloy After Hot Compression Deformation

Japan's Chiba et al conducted a systematic and in-depth study on the microstructure and mechanical properties of cobalt-chromium-molybdenum alloys after hot compression deformation,mainly through a single pass of hot compression deformation to refine the structure and improve the mechanical properties.There are almost no reports on the microstructure and mechanical properties of Co-Cr-Mo alloys after dual-pass and multi-pass hot compression deformation.The research in this article is to further optimize the hot working process and improve the mechanical property of Co-28Cr-6Mo alloy,and this provide theoretical and technological basis of processing for the alloy.In this master thesis,Gleeble-3800 thermal processing simulation testing machine is used to perform single-pass,double-pass and multi-pass hot compression deformation,and the OM,SEM,XRD,EBSD,hardness measurement and tensile property measurement are used to study the effect of hot compression deformation process parameters on the microstructure and mechanical properties of the alloy.The experimental results show that after the Co-28Cr-6Mo alloy solution treated at 1250°C for 2 h was subjected to a single pass of continuous cooling hot compression deformation at strain rate 10⁰ s^-1,true strain 0.9and deformation temperature(1200°C-1100°C),the volume fraction of austenite,the yield strength,the ultimate tensile strength,the elongation and the strength plasticity product are35.10%,630 MPa,1320 MPa,32.04%and 42293 MPa·%respectively.After the Co-28Cr-6Mo alloy solution treated at 1250°C for 2 h was subjected to the first pass of hot compression deformation at deformation temperature 1100°C,strain rate 10^-1 s^-1and true strain 0.55,and then subjected to the second pass of hot compression deformation at deformation temperature 1100°C,strain rate 10⁰ s^-1and true strains of 0.65 and 0.9respectively,with the increasing of the second pass true strain,the volume fraction of austenite,the yield strength,the ultimate tensile strength and the elongation are all increases from 57.45%to 66.80%,from 763 MPa to 812 MPa,from 1326 MPa to 1409 MPa and from19.06%to 22.48%respectively.After the Co-28Cr-6Mo alloy solution treated at 1250?for2 h was subjected to 13 passes(1mm reduction per pass)hot compression deformation(total reduction of 72%)at deformation temperature 1050?and strain rate 10⁰ s^-1,with the holding time between passes(5 s-180 s)increasing,the yield strength decreases from 657 MPa to508 MPa and then increases to 550 MPa,and ultimate tensile strength and the elongation are both decreases from 1438 MPa to 1219 MPa and from 24.26%to 17.22%respectively.After the Co-28Cr-6Mo alloy solution treated at 1250°C for 2 h was subjected to the first pass of hot compression deformation at deformation temperature 1050°C,strain rate 10⁰ s^-1and true strain 0.5,and then subjected to 6 passes(1mm reduction per pass)of hot compression deformation(total reduction of 72%)with the holding time between passes being 30 s,the yield strength,the ultimate tensile strength and the elongation are 579 MPa,1393 MPa and 26.36% respectively.