| S400E high-strength stainless steel is a new type of sorbite stainless steel bearing mainly P element and other alloying elements,has been developed in China compared with commonly used 12Cr13 martensitic stainless steel in earthquake zone and marine industry,it has outstanding characteristics,better corrosion properties and a lower price.It has been stated that S400E exhibits good mechanical property,corrosion resistance and weldability due to the P element.However,the role of P element on the microstructure and corrosion properties has not been understand extensively.In the present thesis,the phase diagram,microstructure and properties of the new S400E sorbite stainless steel was investigated by using Jmatpro phase calculation,metallurgical observation,SEM,EPMA,XRD,Vickers Hardness,Potentiodynamic Polarization and EIS analysis respectively.Moreover,those microstructure and properties were compared with that of 12Cr13 martensite stainless steel on as received and heat treatment condition to explore the role of P element and other alloying elements.The microstructure by SEM and EPMA on as received conditions illustrated that chromium carbide is distributed uniformly in the sorbite stainless steel,but uniformly dispersed in the martensite stainless steel.The calculated phase diagram shows that the increase of the P element content in the sorbite stainless steel will expand the M3P and M（C,N）phase regions,furthermore the calculated phase diagram shows that the S400E sorbite stainless steel temperature from 900℃-1000℃has ferrite and austenite region where as martensite have austenite phase at that temperature,The EIS results from the Nyquist diagram shows that radius of the capacitive resistance arc of S400E is greater than 12Cr13.The Potentiodynamic polarization indicated that sorbite stainless steel has more noble pitting potential than the 12Cr13 martensite stainless steel. |
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