Research Of The Preparation Methods Of High Diamond Content Composite Coating

Diamond particles were added to the coating to prepare the Ni-diamond composite coating. So the coating has a new property and its tribological properties is changed. The content of diamond in the composite coating will have important inf luence on the tribological properties of the coating. In the past studies, the composite coating was prepared by the traditional method, but the volume fraction of the grains in composite coating is difficult to reach 30%. Adding surfactant and other methods can improve the content of particles in the coating, but the promotion is limited and there are some problems in the coating.In order to improve the diamond grains content in the composite coating and the performance of the coating. This paper adopts the inter-sand method, suspension method, electrophoretic deposition and electro-deposition(two-step method) to prepare Ni-diamond composite coating. The three kinds of methods are studied systematically. The effect of diamond particles sizes on the suspension method, inter-sand method and two-step method are studied. The three kinds of methods increase the content of particles in the coating by extending the particle residence time on the surface of the specimen. The differences lie in the inter-sand method and suspension method through gravity, and the two steps through the force of the electric field. The main works and conclusions of this paper are as follows:(1)Study on the inter-sand method. Discuss the experimental parameters of the inter-sand method: temperature, diamond concentration, diamond particles sizes. It was found that the content of diamond particles in the composite coating can be improved effectively by the inter-sand method. The changes of diamond contents in the coating were negatively correlated with temperature. With the increase of the concentration of diamond particles in bath, the content of diamond in the coating firstly increased and then remained unchanged. At 1-2?m, 3-6?m, 6-12?m three kinds of particles sizes, the maximum contents in coating were 43.1%, 51.4%, 61%.(2)Study on the suspension method. Discuss the experimental parameters of the suspension method: temperature, current density, diamond concentration, diamond particles sizes. The study found that the suspension method can signif icantly improve the diamond particles content s. The temperature and current density are negative correlation to the diamond particles contents. The influence trend of the concentration of diamond is the same as that of the inter-sand method. At 1-2?m, 3-6?m, 6-12?m three kinds of particles sizes, the maximum contents in coating were 53.2%, 62.4%, 65.4%.(3)Study on the two-step method. The experimental parameters of two-step method were divided into the electrophoretic deposition and the electro-deposition. Discuss the experimental parameters of electrophoretic deposition: electrophoresis voltage, time, diamond particles sizes. Discuss the experimental parameters of electro-deposition: temperature. It was found that two-step method can greatly improve the diamond content. The increase of the diamond content improved with the increase of the electrophoresis voltage and time, but the increas e was no longer to improve after the diamond content reaching a certain value. When the temperature of plating bath is 45 ?, the effect is the best. At 1-2?m, 3-6?m, 6-12?m three kinds of particles sizes, the maximum contents in coating were 60.1%, 62.2%, 65.5%.(4)Study on the effect of diamond content on the composite coatings' tribological properties. It was found that the increase of the diamond contents and the diamond particles sizes will lead to the decrease of the friction coefficient. With the increase of the diamond contents in the coating, the wear resistance of the coating is greatly improved. When the diamond contents are over 60%, the composite coating is nearly no wear.(5)Study the inter-sand method, suspension method and two-step method ‘s influences on pole sample. The sample placement will have an important impact on particle content in different coating, which is prepared by the inter-sand method and suspension method. The diameter of pole will have an effect on two-step method. When the diameter is 1.5mm, the diamond film is very easy to fall off in the plating bath. When the diameter is 6mm, the coating is smooth and diamond content is higher than that of 1.5mm.