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4692 |
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Microstructure and tribological performance of Cr7C3-(Ni,Cr)3(Al,Cr) coating deposited from Cr7C3 in-situ synthesized alloy powder |
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Hongbin Zhu* / Beijing General Research Institute of Mining and Metallurgy, Beijing Engineering Technology Research Center of Surface Strengthening and Repairing of Industry parts, Fengtai Feng Gao / Beijing General Research Institute of Mining and Metallurgy/Beijing Engineering Technology Research Center of Surface Strengthening and Repairing of Industry parts, Beijing Jie Shen/ Beijing General Research Institute of Mining and Metallurgy/Beijing Engineering Technology Research Center of Surface Strengthening and Repairing of Industry parts, Beijing Yue-guang Yu/ Beijing General Research Institute of Mining and Metallurgy/Beijing Engineering Technology Research Center of Surface Strengthening and Repairing of Industry parts, Beijing Chang-hai Li/ Dept. of Materials and Manufacturing Technology, Chalmers University of Technology, Sweden |
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The work is aimed at developing a new type of Cr7C3-(Ni,Cr)3(Al,Cr) coatings for piston ring used in heavy-duty diesel engine. The feedstock, in which the stripe shaped Cr7C3 was in-situ synthesized, was firstly prepared by melting and gas atomization, then it was subjected to high velocity oxy-fuel(HVOF) thermal spraying to deposited coating. The element composition, microstructures and the phase composition of the powder, as well as the sprayed coating were analyzed by chemical analysis, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanical property and sliding wear performance of the sprayed coating was also tested and compared to a commercial Cr3C2-NiCr and Cr3C2-NiCr-Mo coating used on piston ring. The results showed that the element composition of the feedstock was almost the same as the composition designed and the volume content of Cr7C3 was increased with the more carbon and chromium added. The phases of the sprayed coating was also mainly the Cr7C3 and the Cr doped Ni3Al and the ratio of Cr7C3 was almost no changed when comparing with it in the powder. The microhardness of coating was all increased with the content of Cr7C3 and the highest value was about 1000Hv0.3, but the fracture toughness was just on the contrary. As the optimal matching of hardness with toughness, The coating involved 77vol.% Cr7C3 was showed the improved wear resisrance and lower coefficient of friction than other Cr7C3-(Ni,Cr)3(Al,Cr) coating and commercial coatings. Moreover, as the Cr7C3 presented stripe shape in the coating, the Cr7C3-(Ni,Cr)3(Al,Cr) coating displayed less wear damage to the iron counterpart. Keywords: Cr7C3-(Ni,Cr)3(Al,Cr), HVOF, tribological performance, piston ring |