Tribological Behavior of Tin-Bronze Gradient Self-lubricating Composites

Tin-bronze gradient self-lubricating composites were designed and prepared by powder metallurgy process. The tribological behaviors of the resulting gradient self-lubricating composites sliding against SAE52100 steel in a block-on-ring configuration were investigated on an MM-200 friction and wear tester. The surface morphologies of the wear tracks were observed with a scanning electron microscope. The wear mechanisms of the gradient self-lubricating composites were discussed as well. It was found that the self-lubricating composites showed better friction-reducing and antiwear properties than conventional metal-based lubricating materials at home and multilayer metal-based lubricating materials abroad. They led to negligible damage to the counterpart as well, which was attributed to the formation of a transfer film of the gradient self-lubricating composites on the counterpart surface. The excellent tribological behaviors of the gradient self-lubricating composites were attributed to their special gradient structures, which was characterized by the gradually decreased hardness from the surface to the inner layer and the gradient decreased shearing strength from the inner layer to the surface.