| As the carrier of transmitting power and torque, mill gear directly affect the rolling quality and normal operation of mechanical system. With the working condition of low speed and heavy cycle alternating loads, The boundary film of boundary lubrication gear is easily broken. So the wear is the main failure mode of mill gear. Surfacing is the common processes for site repair of mill gear while it have the problem of energy dispersion, high dilution, high thermal stress and so on. This paper draw the composite technology of laser cladding/laser shock peening into the field of remanufacturing damaged tooth surface, carrying out the research on preparation process of Fe-based alloy/MoS2/La2O3 self-lubricating wear-resistant coating. The main contents are as follow:Preparation and microstructure analysis of self-lubricating wear-resistant coating were carried out. Effect of laser power and powder composition on macro morphology, microstructure, phase and micro-hardness was investigated. Results show the macro morphology of coating was affected significantly by laser power. Width and thickness of A and C coating(wtFe:wtMoS2:wtLa2O3=95:4:1)increased with the growth of laser power, the amplification of thickness of coating became more remarkable. A coating consist of hard phase and tough phase. Compared with A coating, MoS2 and CrxSy lubricating phase were detected on C coating, B4 C and Fe3 C separated out from C coating with the increase of laser power. Effect of laser power and powder composition on microstructure of coating was remarkable. Thickness of white band on bottom of A coating decreased with the increase of laser power, afterbirth-like crystal convert into dendrite crystal gradually. When laser power was 2.2kW, there was undecomposed MoS2 on dendrite crystal in B(wtFe:wt MoS2 =95:5)and C coating compared with A coating, grain density decreased with the decrease of MoS2 content. Hardness of coating tended to increase with the increase of MoS2 content. Hardness of A coating decreased first then increased with the increase of laser power, but hardness of C coating decreased.Experimental comparison of abrasive resistance of substrate, surfacing layer and self-lubricating coating was carried out. The feasibility of self-lubricating wear-resistant coating design was analyzed. Effect of laser power and powder composition on wear-resistant of coating was studied. Results show that under the same friction and wear condition, wear loss of coating was less than substrate and surfacing layer. The feasibility of self-lubricating wear-resistant coating design was verified. When laser power was 2.2kW, wear loss and friction coefficient were decreased firstly then increase, wear loss and friction coefficient of C coating trended to increase with the decrease of MoS2 content. Wear types of substrate were mainly abrasive wear, adhesive wear and fatigue wear. Wear types of A coating were mainly abrasive wear and fatigue wear. Wear types of C coating was fatigue wear,Experimental comparison of abrasive resistance before and after LSP was carried out. Effect of LSP on residual stress, micro-hardness and wear resistance on surface of self-lubricating wear-resistant coating was studied. Results show wear resistance of coating was improved significantly after LSP. Residual tension stress converted into residual compressive stress on surface after LSP, average value of stress decline was 260 MPa. Average micro-hardness of coating increased from 895.1HV0.3 to 932.3HV0.3. Difference value of test point in the same depth trended to decrease along the depth direction, difference value was zero under critical point. Steady friction coefficient decreased from 0.18 to 0.15, wear resistance after LSP was 1.33 times for before LSP. Wear surface was improved significantly after LSP, wear types were mainly fatigue wear before LSP. Surface became smooth after LSP, there was a little fatigue pit on wear surface. |
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