| Super martensitic stainless steel(SMSS)has great application scope in the hydropower industry,oil and gas pipeline transportation.With good plasticity,strength and corrosion resistance,it has gradually replaced duplex stainless steel and super duplex stainless steel.Heat treatment process has great influence on the properties of SMSS.The research object of this paper was 00Cr13Ni5 Mo SMSS,and the influence of quenching temperature,tempering temperature and tempering time on the microstructure and properties of SMSS was investigated.Reverted austenite in the matrix was observed by electron backscattering diffraction analysis(EBSD)and transmission electron microscopy(TEM),and the formation mechanism of reverted austenite was explored.SMSS with strong plastic toughness and high hardness was obtained.These researches are finally applied to industrial production,providing parameter basis and technical support for performance improvement and industrial efficiency of product.The results are as follows:Lath martensite and ferrite are observed after quenching.The lath martensite becomes coarser gradually with the increase of quenching temperature,and the content of residual ferrite after quenching different.The content of δ phase is the least when the quenching temperature is 950℃.The hardness of the test steel reaches 38.7 HRC and the impact energy is 53 J at 950℃.α phase and reverted austenite are observed after tempering.The reverted austenite is distributed at the martensitic lath boundary and the original austenite boundary,and most of the reverted austenite are distributed in the regions with high density of dislocation and high content of nickel.The content of α phase with nickel-rich increases with the increasing tempering temperature from 550℃ to 620℃,and the content of reverted austenite is the highest at 620℃.When the tempering temperature increases from 620℃ to 700℃,the content of reverted austenite decreases.With the increase of tempering time,the content of reverted austenite increases,and it is dispersedly distributed in the matrix after 64 h.After tempering at 620℃,the hardness of the test steel is the lowest value of 26(Rockwell hardness),the impact energy reaches the maximum value of 172.5 J,and the tensile strength is the minimum value of 806 MPa.The longer the tempering holding time,the smaller the hardness,and the greater the impact power.The higher the tempering temperature,the worse the pitting resistance of the material. |
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