【摘要】 为了研究表面纳米化对20Cr钢低温气体渗氮的影响,采用超音速微粒轰击技术(Supersonic Fine Particles Bombarding,SFPB)对20 Cr钢进行了表面纳米化制备,并对其进行了低温气体渗氮处理,利用XRD、TEM和维氏硬度计对处理后试样的组织结构和力学性能进行了测试。结果表明,SFPB处理后20 Cr钢表层平均晶粒尺寸约为19.4 nm,表面硬度达到570 HV,比原始硬度提高了2.73倍。经低温气体渗氮后,SFPB处理层的渗氮层深度随温度的升高而逐渐加深,在450℃渗氮3 h后获得了具有实用价值的化合物层,厚度6~10μm,渗氮6 h后化合物层厚度增加到12-15μm,氮化层深度达到约250μm,表面硬度提高到1185 HV;而非SFPB层在450℃渗氮6 h后表面化合物层仅约2μm,扩散层厚度约50μm。更多还原

【Abstract】 In order to investigate the effect of surface nanocrystalliztion on the low temperature gas nitriding,the surface nanocrystallization is realized on 20Cr steel by using supersonic fine particles bombarding(SFPB),and followed by low temperature gas nitriding.The microstructure was characterized by XRD and TEM,and the hardness was measured by a Vickers hardness tester.The results show that the average grain size of the surface layer for the SFPB 20Cr steel is about 19.4 nm,and the surface microhardness of deformation layer is 570 HV,which is 2.73 times of that of without SFPB treatment.After low temperature gas nitriding of the nanocrystalized 20Cr steel,the depth of nitride layer increases with the increasing nitriding temperature.A compound layer with a thickness of 6-10 μm is formed for the sample after nitriding at 450 ℃ for 3 h.After nitriding at 450 ℃ for 6 h,the compound layer thickness and nitride layer depth are 12-15 μm and about 250 μm,respectively,and the surface microhardness of the nanocrystalized nitride layer is 1185 HV,however,for 20Cr steel without SFPB treatment at the same condition,the compound thickness of the nitride layer is only about 2 μm and the thickness of the nitride diffusion layer is about 50 μm.更多还原