Evaluation of stainless steel back tin-bronze gradient self-lubricating composites

In order to develop a high performance self-lubricating material for bearing inner rings，a kind of stainless steel back tin-bronze gradient self-lubricating composites made of tin-bronze，316L stainless steel and MoS₂ powders was prepared by the multi-billet extrusion method and sintering densification process. This material is composed of supporting layer made of 316L stainless steel powders，solid-lubricating layer mixed with tin-bronze and MoS₂ powders，and transitional layer mixed with the powders of two front layers. The microstructure was characterized by OM and SEM. The wear and physics mechanical properties were investigated by the MTS and friction-wear tester. The results show that the structure of composites is compact，the interface of each layer transits gently under the process of 1050℃ and the holding time 2 h. The hardness and coefficient of friction gradually increase from the solid-lubricating layer to the supporting layer. The measured average density of sintered composites is 8.35 g·cm^-3，and the relative density is 96.8%. The radial crushing strength is 950 MPa. The friction coefficient of working surface of the self-lubricating layer is about 0.30. The micro Vickers hardness of it is 1.44 GPa，and the wear rate is 5.2×10^-9 m·N^-1·m^-1. Compared with  other solid-lubricating materials，the mechanical properties and wear resistance capability of stainless steel back tin-bronze gradient self-lubricating composites are greatly improved.