High Temperature Mechanical Properties Of X3CrNiMo13-4 Martensitic Stainless Steel

X3CrNiMo13-4 martensitic stainless steel(German brand is 1.4313)is widely used in thenuclear power industry owing to its excellent mechanical properties,higher strength,toughness,corrosion resistance and better welding properties,which are able to meet the requirements of being used in guide vanes of the nuclear main pumps.Unfortunately,most of the steels used in nuclear main pumps still have to import from outside.To enhance the independence of the nuclear power equipment manufacture of our country,after the introduction of the third generation of nuclear power technology,AP1000 nuclear power unit,X3CrNiMo13-4 martensitic stainless steel used in domestic vanes has been produced.Higher power nuclear power unit requests better material performance of the guide vanes,especially the fatigue behavior which is very important to nuclear safety.However,research on fatigue behavior of the domestic produced X3CrNiMo13-4 steel has not been carried out yet.Thus,it is of vital importance to analyze the fatigue damage mechanism of X3CrNiMo13-4 martensitic stainless steel,which will further promote the independence of nuclear power industry of our country.In this study,we aimed at the X3CrNiMo13-4 martensitic stainless steel.Through the uniaxial static tensile test at different temperatures,a series of comparative studies on the toughness of the materials were carried out.The shear deformation and the flow stress of the samples under different compression rates were discussed and analyzed through the compression experiments.The axial symmetrical tension and compression fatigue properties at of the material were studied under different temperature,different strain amplitude and different stress amplitude conditions.Through a series of studies on the morphology of fatigue fracture and the initiation and propagation of micro-cracks on the fracture surface,fatigue resistance and cycling response behavior of the steel were evaluated and analyzed.Characterizations of the steel showed that the as-produced X3CrNiMo13-4 martensitic stainless steel is mainly composed of a large number of lath martensite and a small amount of the original austenite.Martensite laths with different orientations existed in the same grain.Dislocation density is lower in the martensite laths in the as-produced steel..Results of uniaxial tensile experiments tested 293℃ showed that the tensile strength and plasticity of the X3CrNiMo13-4 martensitic stainless steel were lower than that tested at room temperature.The compressive strain at 293℃ increases with the increase of strain rates,micro-voids were formed in the intersection of the martensite laths at the shear bands.Phenomenon of dynamic strain aging was found under the lower strain rate loading conditions.Results of High-temperature cyclic loading experiments showed that the low-cycle fatigue properties of X3CrNiMo13-4 martensitic stainless steel were similar which were being tested at 293℃ and 350℃,while the high-temperature high cycle fatigue strength at 293℃ was significantly higher than that at room temperature.At the higher strain amplitudes,phenomenon of cyclic softening happened in the steel until materials fracture failure.While,at the lower strain amplitudes,phenomena of certain extend cyclic hardening happened after cyclic softening due to the formation of dislocation cells in the steel after cyclic loading,which was responsible for the fragmentation of the martensite laths whose duty was bearing the plastic strain.