关键词: 辉光离子渗氮, 奥氏体铸铁, 渗氮层, 耐磨性, 耐蚀性, 组织

Abstract: Nitrided layer was prepared on the surface of Ni15Cu6Cr2 austenitic gray cast iron by glow plasma nitriding at different 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 ε phase and a small amount of γ′ phase with a thickness of about 2 μm 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 10 μm, the ε phase gradually transforms into the γ′ phase, and the thickness of the whole nitrided layer is about 45 μm. 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/cm² to 3.07×10^-7 A/cm².

Key words: glow ion nitriding, austenitic cast iron, nitrided layer, wear resistance, corrosion resistance, microstructure