Effects Of Heat Treatment On Mechanical Properties And Wear Behavior Of Cu-15Ni-8Sn Alloy

Cu-15Ni-8Sn is a high-strength, wear and corrosion resistant copper alloy, which is early used as a high elastic conductive material to replace Beryglium bronze. In recent years, its application in heary loaded and anti-wear environment has received widespread attention. In this paper, Cu-15Ni-8Sn alloy was prepared by normal gravity casting, and the effects of heat treatment on microstructures and properties of Cu-15Ni-8Sn alloy were investigated by mechanical properties test, friction and wear test, metallographic microscopy observation, and scanning electronic microscopy. The main conclusions are summarized as follows:The microstructures of the as-cast and aged alloys were analyzed,and the optimal homogenization annealing process of the as-cast alloy was also explored. The results show that the as-cast alloy has a typical dendrete microstructure which is mainly composed by coarse α dendrite, α+g layer organization, and Sn-riched g phase; The dendritic segregation was totally eliminated and uniform microstructure is obtained after homogenization annealing at 840℃ for 8h; Spinodal decomposition occurred during early aging stage, discontinuous precipitation g phase took place at the grain boundary and growth coarse from grain boundary to transgranular with prolonging aging time.The effects of solid solution and aging treatment on the microstructure and mechanical properties were studied. The results show that homogenized Cu-15Ni-8Sn alloy treated by solid solution at 800℃ for 1h obtained a better mechanical properties than those treated at 780℃ and 820℃ under the same aging condition; The strength of the alloy aged at 400℃ increases firstly then decreases with prolonging aging time and reaches a maximum when aged for about 8h, while the elongation continued to decline along with the aging time; With the aging temperature increasing, the strength and of the alloy increased to a maximum at 400℃ then decreased; The strength and hardness of Cu-15Ni-8Sn alloy are not affected by small amounts of discontinuous precipitation and only weakened when a mass of discontinuous precipitation appeared.The wear properties of the alloys of different heat-treated condition under both dry and oil-lubricated friction conditions were studied. The results show that the wear-resisting property of age treated alloy is much improved compared to the as-cast and solid solution state alloy under both dry and oil-lubricated conditions; The wear volume of alloy aged at 400℃ for different time under both dry and oil-lubricated friction conditions decreased to a minimum at 6h and then increased; The Cu-15Ni-8Sn alloy showed a better wear-resistant property compared with ZBAL16-3-1.5 alloy under both dry and oil-lubricated friction conditions, especially when it comes to a heavy load oil-lubricated condition; Both of adhesive and abrasive wear mechanisms are exist under dry friction condition, and the adhesion resistance of Cu-15Ni-8Sn alloy is obviously enhanced after age treated; The main wear mechanisms are abrasive wear and fatigue spalling wear under oil-lubricated condition, and the fatigue spalling resistance of Cu-15Ni-8Sn alloy is obviously improved after age treated.