辉光离子渗氮奥氏体灰铸铁渗氮层的组织和性能

Microstructure and properties of nitrided layer on austenitic gray cast iron by glow ion nitriding

采用辉光离子渗氮处理在不同温度下(380、540℃)在Ni15Cu6Cr2奥氏体灰铸铁表面制备渗氮层。利用蔡司光学显微镜、扫描电镜、电子探针、X射线衍射仪分析渗氮层的截面组织、元素分布和物相组成;通过磨痕形貌和三维轮廓分析渗氮层的摩擦学性能;采用电化学试验考察渗氮前后奥氏体灰铸铁的耐蚀性。结果表明,经380℃×10 h渗氮处理后,在奥氏体灰铸铁表面获得了厚2μm左右,由ε相和少量γ′相组成的化合物层,表面硬度为330 HV0.05左右。当渗氮温度升高到540℃时,表面硬度提高到900 HV0.05左右,化合物层厚度达到10μm左右,ε相逐渐转变为γ′相,整个渗氮层厚度约为45μm。奥氏体灰铸铁基体的磨损机制为磨粒磨损,经渗氮后逐渐转变为黏着磨损,磨痕宽度逐步变窄,磨痕深度逐渐变浅,耐磨性能得到显著提升。经540℃渗氮后,耐蚀性显著提升,相较于基体自腐蚀电位由-0.337 V增大到-0.217 V,自腐蚀电流密度由1.51×10^(-6)A/cm^(2)减小到3.07×10^(-7)A/cm^(2)。

Nitrided layer was prepared on the surface of Ni15Cu6Cr2 austenitic gray cast iron by glow plasma nitriding at dfferent temperatures(380,540 ℃).The cross-section structure,element distribution and phase composition of the nitrided layer were analyzed by Zeiss optical microscope,scanning electron microscope,electron probe and X-ray diffractometer.The tribological properties of the nitrided layer were analyzed by wear scar morphology and three-dimensional profile.The corrosion resistance of the austenitic gray cast iron before and after nitriding was investigated by electrochemical test.The results show that after nitriding at 380℃for 10 h,a compound layer composed of 8 phase and a small amount of'phase with a thickness of about 2μm is obtained on the surface of the austenitic gray cast iron,and the surface hardness is about 330 HV0.05.When the nitriding temperature rises to 540 ℃,the surface hardness increases to about 900 HV0.05,the thickness of the compound layer reaches about 10μm,the 8 phase gradually transforms into the'phase,and the thickness of the whole nitrided layer is about 45μm.The wear mechanism of the austenitic gray cast iron matrix is abrasive wear,which gradually transforms into adhesive wear after nitriding.The width of the wear scar gradually narrows and the depth gradually becomes shallower,and the wear resistance is significantly improved.After nitriding at 540,the corrosion resistance is significantly improved.Compared with the matrix,the self-corrosion potential increases from-0.337 V to-0.217 V,the self-corrosion current density decreases from 1.51×10^(-6) A/cm^(2) to 3.07×10^(-7) A/cm^(2).