Study On Microstructure And Friction And Wear Properties Of Fe-based Self-lubricating Coating By Laser Cladding

Improving the friction and wear properties of metal alloy materials through surface wearresistant coatings,surface treatment,and post treatment has significant economic and social value as the world’s energy reserves continue to decline,non-renewable material resources,and environmental issues become more prominent.,surface treatment,and post treatment has important economic and social value.Under certain specific friction conditions,the friction components themselves should not only have anti wear and friction reduction performance,but also ensure good wear conditions for the wear parts.In response to these problems,a selflubricating coating of Fe-based Ni/MoS2 and Cu was designed using 40Cr steel as the base material for this article.The effects of various solid additives on the coating’s phase,microstructure,and microhardness were investigated..Under conditions that resembled tire vulcanization,studies on friction and wear were performed..The mechanism of the modified coating protecting the tire mold from wear was studied.After sulfurizing,cryogenic treatment,and heat treatment,the produced Fe-based coating’s friction and wear characteristics were investigated..The main work is as follows:(1)The impacts of various Ni/MoS2 and Cu material ratios on the cladding layer’s microstructure and microhardness were investigated..The main phase components of the C1 Fe-based coating in the five new alloy powders designed(C1:FeCrNiMo,C2:FeCrNiMo+10 wt.%Ni/MoS2,C3:FeCrNiMo+20 wt.%Ni/MoS2,C4:FeCrNiMo+20 wt.%Ni/MoS2+10 wt.%nano copper,and C5:FeCrNiMo+20 wt.%Ni/MoS2+10 wt.%micron copper)are martensite,residual austenite,M7C3 hard carbide phase,and Fe-based solid solution.The hard phase in the Febased coating can be eliminated by the in-situ generated CrxSy self-lubricating phase,which helps to reduce wear on abrasive parts.Micron copper forms large and bright particles in the coating,while nano copper dissolves in the grains.(2)The mechanism of the Fe-based composite coating prepared to protect the wear parts from wear in the tire vulcanization mold friction pair was studied.During friction and wear with a pair of wear parts(40Cr nitrided layer of tire mold)under simulated vulcanization conditions,the soft metal Cu and CrxSy in the C4 and C5 coatings cooperate to form a complete lubricating film,forming a "hard soft hard" layered structure for the friction pair,avoiding the wear of the 40Cr nitrided layer.The wear resistance is higher than the Cu-based wear resistant plate used in the original design.(3)The microstructure and wear resistance of laser-clad Fe-based coatings were examined in relation to the impacts of sulfurizing,heat treatment,and cryogenic treatment.The hardness,phase composition,and microstructure of the coating were studied using a Vickers hardness tester,X-ray diffractometer(XRD),and scanning electron microscope(SEM),respectively.A dry sliding wear test was conducted using a CETR UMT-2 ball to disk wear tester at 25℃ and a load of 20 N for 1 hour.The test showed that several post treatment methods greatly improved the wear resistance of the coating.Under the same wear conditions,sulfurizing has the smallest wear volume,which is only 27%of the Fe-based coating.The second smallest wear volume is cryogenic treatment,and a large amount of fine carbide is dispersed in the substrate of the sample after cryogenic treatment.During the wear process,fine carbides are not easy to fall off,improving the stability and bearing capacity of the material.The wear resistance increases,the wear volume steadily reduces,and the wear surface gets smoother as the heat treatment temperature rises.