The Copper Alloy Surface Infiltration Casting

The study of surface modification of materials has become an important embranchment in the field of materials development. The technique is a kind of modification for strengthening the surface capability that doesn't change the basal capability of raw material. This technique would make the capability fit the requirement of the modern technique. The surface modification not only enhances the lifespan of the parts and reduces the wear but also increases the economic situation in largely extent.There are methods of surface modification such as heat treatment, a discharge of electricity from low gas penetrating S, plasma spraying and so on for copper and copper alloy. These methods need special equipment and its manufacturing cycle is long, so the cost is high. The casting- penetration method was used in this paper. The process is a kind technique of surface transacting through pouring metal liquid to the mould that has been pasted a layer of alloy powder ahead. Casting-penetration takes advantage of the remainder heat of solidification to let the powder melt, decompose, diffuse and at last form a layer of special capability on the surface of the cast. As for the copper alloy, its coefficient of storing heat is small and the velocity of solidification meanwhile easily absorbing gas and oxidation is quick, forming the penetration layer on the copper alloy surface is more difficult than other alloy surface. Aiming at these problems we chose the powder of self-fusibility (Ni60). The main factors that influencing the forming of the penetration layer are pouring temperature, preheating temperature, adopting the negative press or not, layer thickness pasted ahead and the binder. The optimum parameter of process are: pouring temperature (1180~ 1200℃), preheating temperature (100~ 150 ℃) the negative conditions (-0.04~0.06MP), layer thickness pasted ahead(2~ 3 nim) and the binder (the joining quantity of latex 3 ~ 5 % ). On basis of assuring the all kinds of conditions above-mentioned we acquired penetration layer on the surface of copper alloy. The microstructure of the penetration layer is good, the interface between the base metal and the penetrated layer doesn't exist hole and the structure is compact through the microscope and SEM. Its surface hardness can reach HRC50. Its anti-wear capability behaves well. But the layer is thinner. So the layer of powder that has definite hole-rate was used to pour the cast. The layer with definite hole- rate through joining definite quantity boric acid into the powder was obtained then having heating transacting toward it. The study show that the proportion between the powder and the boric acid must have been controlled at ranging 9: 1 to 12: 1. The penetrated layer has been advanced obviously. The powder of Cr-Fe is used in this experiment(in the last time of experiment the penetrated layer could not acquire using the Cr-Fe powder). There is some inclusions and hole in the microstructure through the microscope and SEM, but the surface hardness could reach HRC25~40. The anti-wear capability has been improved.If the process of the casting-penetration could be stabilized and apply it to the industrial production, this technic would have been applied in the field of anti-wear parts, bearing high temperature parts and anti-eroded parts. This process unites the two processes of molding and surface modification as one process. This technics could bring large economic and social benefit for the development and has a promising future.