The mechanical properties and wear resistance of the ultrafine bainitic steel austempered at various temperatures were investigated.Scanning electron microscopy(SEM)and X-ray diffraction were used to analyze the micro...The mechanical properties and wear resistance of the ultrafine bainitic steel austempered at various temperatures were investigated.Scanning electron microscopy(SEM)and X-ray diffraction were used to analyze the microstructure.The worn surfaces were observed via laser scanning confocal microscopy and SEM.Results indicated that,under low austempering temperatures,the mechanical properties differed,and the wear resistance remained basically unchanged.The tensile strength of the samples was above 1800 MPa,but only one sample austempered at 230°C had an elongation of more than 10%.The weight loss of samples was approximately linear with the cycles of wear and nonlinear with the loads.The samples showed little difference in wear resistance at different isothermal temperatures,whereas the thickness of their deformed layers varied greatly.The results are related to the initial hardness of the sample and the stability of the retained austenite.Meanwhile,the experimental results showed that the effect of austempering temperature on the wear resistance of ultrafine bainitic steel can be neglected under low applied loads and low austempering temperature.展开更多
Quantum-chemical calculations of polyatomic clusters simulating a boundary between grains in a surface layer of steel were carried out. Along with iron atoms the clusters contain atoms of alloying and impurity element...Quantum-chemical calculations of polyatomic clusters simulating a boundary between grains in a surface layer of steel were carried out. Along with iron atoms the clusters contain atoms of alloying and impurity elements which appear on the boundary due to grain boundary segregation or intergrain diffusion. The influence of the chemical composition of a segregate on the strength of coupling between grains and, eventually, on steel wear resistance is analyzed. Results obtained show that the degree of the strength of binding of segregated atoms with atoms of iron in a metal surface layer is an essential factor influencing wear resistance. It is found that the dependence of energy of binding of atoms of different elements with grain surface on the atomic number complies with the periodic law. This fact can be considered as a theoretical base for the prognostication of strength properties of steel with different composition of alloying and impurity elements. Potential energy curves corresponding to the movement of atoms on iron surface are studied. They can be useful for design of the composition of multi-layer coats on steel.展开更多
The influences of trace alloying elements niobium, vanadium and zirconium on the corrosive resistance of 18 8 type cast stainless steel have been studied in detail by orthogonal design experiments. The results show th...The influences of trace alloying elements niobium, vanadium and zirconium on the corrosive resistance of 18 8 type cast stainless steel have been studied in detail by orthogonal design experiments. The results show that zirconium is mainly in the form of compound inclusions, which is unfavorable to promote the corrosive resistance of the cast stainless steel. It can alleviate the disadvantageous influence of carbon addition on corrosive resistance when some elements such as vanadium and niobium exist in the steel, and niobium has a remarkable influence on the intergranular corrosive resistance but unobvious on the pitting corrosion, and vanadium has a slightly favorable influence on the corrosive resistance of the steel.展开更多
The sliding wear property of high-carbon nanostructured bainitic bearing steel with the equal initial hardness and different microstructures was investigated,and the reasons for the difference of wear resistance betwe...The sliding wear property of high-carbon nanostructured bainitic bearing steel with the equal initial hardness and different microstructures was investigated,and the reasons for the difference of wear resistance between the cementite-bearing(CB)and cementite-free(CF)specimens were analyzed.The results show that CF specimens have lower mass loss and surface roughness and shallower wear depth than CB specimens during wear process.Compared with CB specimen,CF specimen presents superior wear resistance.This is due to two reasons:(1)a lot of retained austenite in CF specimen is easy to produce TRIP effect and be transformed into martensite during wear process,which notably increased the surface hardness of worn specimen;(2)there is a nondestructive oxide layer in the surface of cementite-free worn specimen,which can protect the surface of worn specimen from destruction.Under the combined effect of retained austenite and oxide layer,the loss of matrix is reduced.Thus,CF specimen exhibits high wear resistance.It reveals that the wear mechanism of high-carbon nanostructured bainitic bearing steel with different microstructures can provide a reference for improving the wear resistance in high-carbon nanostructured bainitic bearing steel in future.展开更多
基金the National Key Research and Development Plan of China(No.2016YFB0300205)the National Natural Science Foundation of China(Nos.U1810207 and 51601174).
文摘The mechanical properties and wear resistance of the ultrafine bainitic steel austempered at various temperatures were investigated.Scanning electron microscopy(SEM)and X-ray diffraction were used to analyze the microstructure.The worn surfaces were observed via laser scanning confocal microscopy and SEM.Results indicated that,under low austempering temperatures,the mechanical properties differed,and the wear resistance remained basically unchanged.The tensile strength of the samples was above 1800 MPa,but only one sample austempered at 230°C had an elongation of more than 10%.The weight loss of samples was approximately linear with the cycles of wear and nonlinear with the loads.The samples showed little difference in wear resistance at different isothermal temperatures,whereas the thickness of their deformed layers varied greatly.The results are related to the initial hardness of the sample and the stability of the retained austenite.Meanwhile,the experimental results showed that the effect of austempering temperature on the wear resistance of ultrafine bainitic steel can be neglected under low applied loads and low austempering temperature.
文摘Quantum-chemical calculations of polyatomic clusters simulating a boundary between grains in a surface layer of steel were carried out. Along with iron atoms the clusters contain atoms of alloying and impurity elements which appear on the boundary due to grain boundary segregation or intergrain diffusion. The influence of the chemical composition of a segregate on the strength of coupling between grains and, eventually, on steel wear resistance is analyzed. Results obtained show that the degree of the strength of binding of segregated atoms with atoms of iron in a metal surface layer is an essential factor influencing wear resistance. It is found that the dependence of energy of binding of atoms of different elements with grain surface on the atomic number complies with the periodic law. This fact can be considered as a theoretical base for the prognostication of strength properties of steel with different composition of alloying and impurity elements. Potential energy curves corresponding to the movement of atoms on iron surface are studied. They can be useful for design of the composition of multi-layer coats on steel.
文摘The influences of trace alloying elements niobium, vanadium and zirconium on the corrosive resistance of 18 8 type cast stainless steel have been studied in detail by orthogonal design experiments. The results show that zirconium is mainly in the form of compound inclusions, which is unfavorable to promote the corrosive resistance of the cast stainless steel. It can alleviate the disadvantageous influence of carbon addition on corrosive resistance when some elements such as vanadium and niobium exist in the steel, and niobium has a remarkable influence on the intergranular corrosive resistance but unobvious on the pitting corrosion, and vanadium has a slightly favorable influence on the corrosive resistance of the steel.
基金The authors acknowledge financial support from the National Key R&D Program of China(2017YFB0304501)the National Natural Science Foundation of China(Nos.51831008,51871192 and 52001275)+1 种基金the Natural Science Foundation of Hebei Province(E2020203058,E2018203271)the Innovation Funding Project for Postgraduate of Hebei Province(CXZZBS2020058).
文摘The sliding wear property of high-carbon nanostructured bainitic bearing steel with the equal initial hardness and different microstructures was investigated,and the reasons for the difference of wear resistance between the cementite-bearing(CB)and cementite-free(CF)specimens were analyzed.The results show that CF specimens have lower mass loss and surface roughness and shallower wear depth than CB specimens during wear process.Compared with CB specimen,CF specimen presents superior wear resistance.This is due to two reasons:(1)a lot of retained austenite in CF specimen is easy to produce TRIP effect and be transformed into martensite during wear process,which notably increased the surface hardness of worn specimen;(2)there is a nondestructive oxide layer in the surface of cementite-free worn specimen,which can protect the surface of worn specimen from destruction.Under the combined effect of retained austenite and oxide layer,the loss of matrix is reduced.Thus,CF specimen exhibits high wear resistance.It reveals that the wear mechanism of high-carbon nanostructured bainitic bearing steel with different microstructures can provide a reference for improving the wear resistance in high-carbon nanostructured bainitic bearing steel in future.
