Study Of Fe-Ni-C-Si Self-lubricating Material

Fe-Ni-C-Si self-lubricating material with different silicon addition to spur the generation of graphite was prepared by melting method. The effect of silicon content on alloy's structure was studied. The results show that the melting method had many merits VS power metallurgy method, such as the dense and homogeneous structure. With increasing of silicon content, the quantity of carbon atom melting to the austenite decreases, the number of silicon atom increases and the flake graphite will be stubby and spherical. According to the analyses of alloy's phases, we find that the phases of alloy that the nickel content is 30% are austenite and graphite, and find that when the nickel content reduce to 20%, the phases of alloy is austenite, graphite, ferrite and Ni3Fe.The effects of silicon contents on the mechanical properties were investigated. The results show that the hardness, the tensile strength and the flexural strength increased with increasing of silicon content. But when the silicon content was 2.5%, they will reach the maximum, and the impact flexibility is on an inverse trend. The fracture mechanism was different, when the content of nickel is different. If the nickel content was 30%,the fracture mechanism was intergranular fracture, the else was gliding fracture.The values of the coefficient of thermal expansion are from 9.8×10-6K-1 to 13.23×10-6K-1 which are lower than the spheroidal graphite casting whose coefficient of thermal expansion is 13.5×10-6k-1. With the increasing of silicon contents, the area density of graphite increases at first and then reduces. But the density of the alloy show inverse trend.The results of friction and wear experiments showed that the shape of the graphite and the hardness of the alloy make a great role in the performance of dry-friction. The massive flake graphite was easy to form a steady graphite enrichment layer which can strengthen the effect of lubrication. It is found that high hardness can protect the graphite enrichment layer, and the abrasion mechanism is fatigue-abrasion. Among the alloys, the Fe-20%Ni-3.5%C-0.5%Si, which dry friction coefficient is remained stably as 0.18, have the best performance of dry friction. Under the condition of oil lubrication, which abrasion mechanism is grain-abrasion,...