Research On Friction And Wear Properties Of B-C-S Composite Layer For 2Cr13 Stainless Steel

Martensitic stainless steel is mainly used in the manufacture of steam turbine blades,valves,bearings,cutting tools,medical equipment for its excellent mechanical properties and corrosion resistance.However,its low hardness and poor wear resistance become the major obstacles for the further application.In order to solve these problems,the B-C-S composite infiltration layer on the surface of 2Cr13 martensitic stainless steel has been prepared by powder packing cementation method in this paper.The purpose of this method is to combine hardness and lubrication so that the 2Cr13stainless steel surface forms an ideal tribological surface,thereby achieving the effect of anti-friction and wear-resistance.The borocarburizing layer on the surface of 2Cr13 martensitic stainless steel has been prepared by pack boriding.The effects of holding temperature and holding time on the microstructure,thickness and surface hardness of the borocarburizing layer were studied,and the process parameters were optimized.Then a sulfurized layer was prepared on the surface of the borocarburizing layer.The morphology,element distribution and phase composition of the borocarburizing layer and B-C-S composite infiltration layer were analyzed by SEM,EDS and XRD.A series of mechanical properties of the two layers were measured.Finally,the tribological properties of 2Cr13 steel substrate,borocarburizing layer and B-C-S composite infiltration layer under different loads and friction pairs were compared by ball-on-disk wear tester.The wear mechanism of the composite infiltration layer was analyzed.The results show that:（1）The best process parameters for pack borocarburizing are holding temperature of 950°C and holding time of 10 hours;subsequent solid sulfur infiltration process is holding temperature of 550°C and holding time of 6 hours.（2）The thickness of the borocarburizing layer prepared under the optimal process parameters is about 139μm,and the infiltrated layer is well bonded to the substrate.Its phase composition is mainly Fe B phase,Fe₂B phase,and Fe₃C phase,etc.The surface nano-hardness of the borocarburizing layer reaches 17.71 GPa,which is approximately 5times higher than that of the substrate.The elastic modulus of the borocarburizing layer is 266.01GPa,which is 22%higher than that of the substrate.（3）The thickness of the sulfurized layer was about 18μm.XRD diffraction results showed that the main phases of the composite layer were FeS phases,FeS₂phases,Fe B phases and Fe₃C phases.Its surface roughness value is about 1.643μm,which is reduced compared to the surface roughness value 2.975μm of the borocarburizing layer.The nanohardness and elastic modulus（2.41GPa and 59.68GPa）of the composite layer are lower.The B-C-S composite layer constitutes an ideal tribological surface structure.（4）The ball-disk wear tests show that the B-C-S composite layer combines the good lubrication of the sulfurizing layer and the superior wear resistance of the borocarburizing layer under different load and friction pair conditions.The change of friction coefficient is significantly lower than that of the substrate,and the wear volume,wear rate and wear rate of the composite layer are also significantly reduced compared to the substrate.The wear mechanism is mainly a small amount of abrasive wear,the B-C-S composite layer showing excellent properties of anti-friction and wear-resistance.