Influence Of Remelting Process On Thestructure And Performance Of The Co60 Coating By Flame Spraying

In this paper, author used oxyacetylene flame spraying method to prepare of Cobalt-based self fluxing alloy powder coating in 20CrMo steel substrate.The 20CrMo steel was often used to make the three cone bit. It used orthogonal experiment method to discuss the influence of the different technological parameters. It choosed the best technological parameters and coats by argon arc remelting processing investigating the changes of the organization and properties after the remelting, analyzing the effection of coating structure and performance after remelting in different radio of the powder composition. X-ray diffractionand other laboratory equipment was used to study organization structure and performance of layer of spray before and after argon arc remelting. The best powder composition was found to strengthen and repaire the three cone bit.The results show that Oxyacetylene flame spraying combination between coating and substrate is mainly mechanical bond, tracing the metallurgical combination of complementary. Coating is layered organization. Coating contains the deformation of particles, oxide, not melt particlesand porosity. When the spray layer thickness to 1.0 mm,substrate surface roughness is 6.89μm, spraying distance is 100 mm, comprehensive performance is best.The primary and secondary ralationshios of process parameters affecting the overall performance are spraying distance,coating thickness with substrate roughness.Through the tungsten electrode argon arc remelting processing,the shape of flame spraying layer and substrate is metallurgical bonding. The remelting layer is splited into three parts:the remelting part, combining part, heat affecting part. The combining zone grows with flat crystal and coarse celluar crystal.The remelting organization near the combining zone is relatively coarse columnar crystals.The core part of remelting layer is uniform size of columnar crystals and dendrites. Heat affecting part is wilcoxon organization, the organization is relatively bulky. Cobalt-based composite powder remelted layer composes by γ-Co, （Cr,Fe）₇C₃, Cr₂₃C₆, Co₆W₆C, WC.After remelting processing,the hardness,wear resistance of the layer improves significantly. When adding 15 percent of WC and 10 percent of CrFe in the powder,remelting layer contains the strongest hardness and wear resistance,the maximum of the rockwell hardness is HRC67.7,the microhardness is HV927.3,the minimum of wear loss is 0.02g.The corrosion loss is 0.09g.In this paper,the best technology parameters are that the thickness of the coating is 1.0mm,the roughness of the substrate surface is 6.89μm, the spraying distance is 100mm.The best powder composition is 15%WC and 10%CrFe.The author uses them to strengthen and repaire the three cone bit.