Study On Microstructure And Mechanical Properties Of PH13-8Mo Stainless Steel

PH 13-8Mo stainless steel is a martensitic precipitation hardening stainless steel.It has high strength and hardness,good toughness and ductility,good weldability,and corrosion resistance.Widely used in aerospace,ocean engineering,nuclear power equipment,petrochemical,and other fields.In this paper,we use X-ray diffractometer(XRD),scanning electron microscope(SEM),electron backscatter diffraction technique(EBSD),transmission electron microscope(TEM),and other characterization instruments,The structure is analyzed.the mechanical properties are analyzed by tensile testing machine,pendulum impact testing machine,rockwell hardness tester,etc.The effects of different aging heat treatment processes on the microstructure and mechanical properties of PH 13-8Mo stainless steel were studied by calculating the phase composition diagram of the equilibrium state with thermodynamic calculation software Jmatpro.The research contents and results of this paper are as follows:(1)Effect of CCT curve and solution cooling rate on mechanical properties of PH 13-8Mo stainless steel.The CCT curve of the PH 13-8Mo stainless steel shows that only martensitic transformation occurs in the cooling process of the experimental steel,but no other microstructure transformation occurs.Oil cooling is used for solution treatment in industrial production.(2)Effect of aging temperature on microstructure and mechanical properties of PH 13-8Mo stainless steel.The microstructure at the single aging temperature is lath martensite,reversed austenite,and dispersed precipitate Ni Al.With the increase of aging temperature,the content of reversed austenite increases,the size of Ni Al phase gradually becomes larger,the volume fraction decreases,so that the strength and hardness are reduced,and the plastic toughness is improved.Furthermore,the theoretical yield strength was calculated by the microstructure,and the strengthening mechanism of PH 13-8Mo stainless steel was quantitatively evaluated.It was found that the precipitation strengthening effect was most significant at the aging temperature of 510℃.(3)Effect of different aging holding time on microstructure and mechanical properties of PH 13-8Mo stainless steel.After aging treatment,the structures are still lath martensite,reversed austenite and Ni Al precipitates.With the gradual extension of holding time,the reversed austenite content is gradually increased,the strength and hardness are gradually reduced,and the impact toughness is constantly improved.And the formation mechanism of reversed austenite is explained.With the extension of the final aging time,the strength decreases slightly and the impact toughness remains unchanged.