Study On Coordinated Deformation Behavior Of Wear Resistant And Wear Reducing Copper/PTFE Coating On Steel Plate Surface

With the development of industry,oil-free or oil-less lubrication is required under many working conditions.Self-lubricating metal matrix composites are more and more widely used with its excellent mechanical properties as well as friction and wear properties.In this paper,wear resistant and wear reducing copper/surface poly tetra fluoroethylene(PTFE)coating on steel plate materials are prepared with raw materials include steel plate,copper powder and PTFE.The structure analysis and mechanical properties tests are carried out to study the influence of structure on its mechanical properties.Digital image correlation(DIC)technology and in-situ electron backscattered diffraction(EBSD)technology are used to analyze the strain distribution and evolution of steel/copper/PTFE composites during in-situ stretching and bending and to analyze the microstructure evolution law of wear resistant and wear reducing copper/surface poly tetra fluoroethylene(PTFE)coating on steel plate materials in the stretching process respectively.The wear resistant and wear reducing copper/PTFE coating on steel plate materials was prepared by sintering and rolling.The results of microstructure observation showed that the steel plate and the copper powder were combined through diffusion reaction,and the PTFE was embedded in the pores between the copper powder to achieve mechanical bonding.Microstructure analysis shows that during the preparation process,the steel plate has recovered and recrystallized,and the grains have grown slightly,but the rolling texture of{100}<011>and{111}<112>is still retained.The room temperature tensile test of wear resistant and wear reducing copper/PTFE coating on steel plate materials material shows that the strength of steel/copper/PTFE composite material is higher than the strength calculated by the law of mixing,which shows that the layered structure and the structure of PTFE embedded in copper powder are effective to increase its strength.The in-situ tensile test results based on DIC show that the strength of PTFE has been exhausted and cracked have occurred in the elastic stage of the steel plate and copper powder.In the longitudinal?_yy direction,the compressive strain variable of the copper/PTFE layer is significantly smaller than that of the steel plate layer.As a result,the amount of lateral shrinkage on both sides of the steel plate is different,which causes the bending of specimen.The experimental results of in-situ bending based on DIC show that at the initial stage of deformation,the softer PTFE is squeezed by copper powder.Stress concentration occurs at the interface between PTFE and copper powder,and then gradually transferred to the steel plate.The in-situ tensile test results based on EBSD show that due to the small deformation of the copper powder,the crystal grains at the steel/copper interface in the steel plate are constrained by the interface,and the deformation is small.Under the limitation of the steel/copper/PTFE composite plate structure,the rotation of Fe crystal grains during the stretching process is different from that of a single-layer low-carbon steel plate,which is beneficial to alleviate the strain localization of the steel plate.Using X-ray tomography(CT)to analyze the size,shape and distribution of the internal pores of the shaft sleeve made of wear resistant and wear reducing copper/PTFE coating on steel plate materials,the results showed that the larger pores in the samples with severe cracking degree accounted for a larger volume;The pores between the copper powders in the severely cracked samples are more distributed farther from the surface,and their shapes are mostly narrow and deep.The pores are difficult to be filled with PTFE completely.The pores between the copper powders in the samples that have not fallen off are the distribution is closer to the surface,mostly wide and shallow,which is facilitate to be filled with PTFE.