| Austenitic stainless steel(ASS)is the most widely used and widely used steel type in stainless steel.The annual production of it account for two-thirds the world total production of stainless steel.Because of its excellent deformation property,welding property and superior corrosion resistance property,which has been widely applied in the field of food,medical,aerospace and chemical industries.However,due to its extremely low hardness,cause the wear resistance property is very poor,which lead to easily failure of mass components and parts even under low load according to the serious wear.In addition,ASS can not occur phase transformation with the temperature,so it is impossible to be strengthened by heat treatment like other common steel materials.As a green and nontoxic compound treatment technology,QPQ technology can remarkable enhance the wear resistance and corrosion resistance and fatigue strength for iron-based materials,which also is regarded as an advanced surface reinforcement technology.Although traditional QPQ technology also can obviously improve the wear resistance and corrosion resistance and fatigue strength,it will seriously damage the excellent corrosion resistance of ASS,which seriously limit the implication of QPQ technology to ASS now.The low temperature can both improve the hardness and wear resistance without damage its corrosion resistance to ASS,which has profound practical significance.This experiment used 304 austenitic stainless steel as experiment materials.First select the best effective accelerator from four RE compound and then tested by orthogonal design to inspect four influence factors of low-temperature QPQ technology which includes nitiding temperature,nitriding time,nitriding concentration and REE(Y2(CO3)3)content for the nitrieding layer,and the judgment standard includes surface hardness and the self-corrosion potential.Systematic and comprehensive optimizing low-temperature QPQ technology processing parameters to ASS.And then inspect the optimizing QPQ technology by testing nitriding layer.The mechanical properties and resistance to intergranular corrosion after the optimizing process have been tested according to the national standard.The main purpose of improving the wear resistance without reducing the corrosion resistance of austenitic stainless steel has been achieved,and the feasibility of the process was proved.The main conclusions are as fillows:1.It was found that that effect of the osmotic effect is yttrium carbonate at the x content of the four rare earth seeping agent in lanthanum chloride,cerium chloride,yttrium chloride and yttrium chloride.2.The best process parameters of low-temperature QPQ technology is that the nitriding temperature is 450?,nitriding time is 4h,nintriding concentration is 40% and the REE content is a.3.Through metallographic microscope,XRD,Viker's hardness tester and SEM to studied the permeability layer's microstructure,phase composition and surface hardness.The result suggest that the nitrided layer is composed of phase S and its thickness is about 10?m and the surface hardness is 994HV0.025 which five times to untreated by the optimizing process treated.The corrosion resistance of optimizing process treated have been demonstrated it is improved by polarization test.4.Through the tensile test and impact test to detect the change of mechanical property with the national standard GB/T 228 and 229.The test results show that the yield strength and tensile strength of ASS after optimizing process treated are improved,the impact energy is basically unchanged,and the results also meet the rational standard.The results demonstrate that the resistance to intergranular corrosion of the material after optimization treatment is slightly decreased after optimizing process treated according to the correlative national standard.However,because the impact absorption work is basically the same,the outer layer is protected by the S phase layer,and the corrosion resistance of the material is enhanced by a certain degree. |
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