The morphology and properties of Nitrocarburized layer of lzqt600-3profile at different positions were studied. The microstructure of the nitrocarburized samples was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The thickness of the nitrided layer was measured and counted by Image J software. At the same time, the hardness, wear resistance and friction and wear mechanism of the nitrocarburized samples were investigated by micro Vickers hardness tester and friction and wear tester, and the results were analyzed by range and variance. The main conclusions are as follows
(1) The compound layer of nitrided layer of lzqt600-3 ductile iron profile is composed of oxide layers (OLS), compound layers (CLS) and diffusion layers (DLS). XRD analysis shows that the layer is composed of compound layer composed of ε – fe2-3 (n, c) phase and γ′ – Fe4N phase and diffusion layer composed of α – Fe phase.
(2) The results show that the influence of nitriding parameters on the thickness of nitrided layer of lzqt600-3 ductile iron profiles is in the following order: nitriding time t > gas proportion s > nitriding temperature T. the optimal scheme is 580 ℃ × 6 h, NH3: CO2 is 4:1.
(3) The influence of nitriding parameters on surface hardness of lzqt600-3 nodular iron profile in three parts is as follows: nitriding time t > nitriding temperature T > gas ratio s. The optimal scheme is 560 ℃ × 4 h, NH3: CO2 is 4:1.
(4) The influence of nitriding parameters on microhardness (effective hardened layer depth) of lzqt600-3 nodular iron profile in three parts is as follows: nitriding temperature T > gas proportion s > nitriding time T. the optimal scheme is 540 ℃ × 2 h, NH3: CO2 is 4:4.
(5) The influence of nitriding parameters on the comprehensive score of friction and wear properties of lzqt600-3 nodular iron profile in three parts is as follows: nitriding temperature T > gas proportion s > nitriding time T. the optimal scheme is 580 ℃ for 4 h, NH3: CO2 is 4:1.
(6) The results show that there are obvious furrows on the surface of as cast and nitrocarburized samples after friction and wear experiments. With the increase of testing time, the as cast samples change from slight adhesive wear to more serious adhesive wear. The joint action of adhesion wear and abrasive wear is caused by the presence of hardening phase on the surface of Nitrocarburized samples The results show that the friction coefficient and wear rate of the samples are the highest, which means that the wear resistance of the samples is obviously improved.
(7) Through the comprehensive balance method, the optimal conditions of the four indexes were compared and analyzed, and the optimal scheme was obtained as follows: 580 ℃ × 4 h, NH3: CO2 4:1.