| Wear and contact fatigue are the most important surface failure form of rotating parts.While plasma spraying is an effective technology to repair the surface.Due to there are pores,microcracks,unmelted particles and a lamellar structure in the as-sprayed coating,as well as the bonding between the coating and the substrate is mechanical combination.Thus,the application of the plasma sprayed coating is limited.At present,laser remelting,electron beam remelting,flame remelting and tungsten inert gas remelting are the post treatment technology to improve the microstructure and performance of plasma sprayed coatings.Therefore,in order to expand the application scope of plasma sprayed coatings,it is necessary to intensively study the influence of remelting treatment on the microstructure and properties of plasma sprayed coatings.In this work,the effect of tungsten inert gas remelting on the microstructure,mechanical properties,wear and rolling contact fatigue properties of FeCrBSi plasma sprayed coatings were studied.Firstly,the microstructure and phase composition of the coatings before and after remelting were analyzed with scanning electron microscope(SEM),energy spectrum analyzer(EDS),X ray diffractometer(XRD)and transmission electron microscope(TEM).Secondly,the microhardness,elastic modulus and fracture toughness of the as-sprayed coating and remelted coating were measured by microhardness tester and nano-indenter.Thirdly,the bonding strength between the coating and substrate was evaluated by tensile method.Finally,the wear properties of as-sprayed coating and remelted coating under different loads and contact fatigue properties under different sliding rates were tested by wear tester and rolling-sliding contact fatigue tester,respectively.The results showed that:(1)After remelting,the pores,microcracks and unmelted particles in the as-sprayed coating were eliminated,as well as the compactness of the coating was improved.Compared with the as-sprayed,the elastic modulus,microhardness and fracture toughness of the remelted coating were increased by 53.2%,33.4% and 287.6% respectively.The bonding mode between the coating and substrate was changed from mechanical bonding to metallurgical bonding,which improved the bonding strength between the as-sprayed coating and the substrate.(2)In the friction and wear experiment,the wear volume of remelted coating respectively decreased by 32.1%,51.5%,60.7% and 55.7% under 10 N,20N,30 N and 40 N loads than that of the as-sprayed coating.The wear resistance of as-sprayed coating was improved significantly by argon arc remelting.The failure modes of as-sprayed coating were spalling and abrasive wear,showing brittle fracture characteristics,and that of remelted coating is adhesive wear and fatigue wear,displaying plastic deformation and pear groove characteristics.(3)In the rolling/sliding contact fatigue test,the characteristic life of remelted coating was longer than that of as-sprayed coating,and the remelting treatment significantly improved the fatigue resistance of the as-sprayed coating.Surface abrasion,spalling and delamination were three typical modes of as-sprayed coating and remelted coating.The failure modes of the as-sprayed coating was delamination,while the failure modes of the remelted coating were abrasion and spalling.The delamination failure was due to poor adhesive strength;The abrasion failure was mainly related to the microsliding between the contact pair and the remelted coating;The spalling failure was related to the maximum shear stress.(4)In the fatigue process,the acoustic emission signal mainly included four stages:normal contact,fatigue crack initiation,fatigue crack propagation and material loss.The fatigue crack propagation stage of as-sprayed coating was shorter than that of remelted coating,thus,the failure of as-sprayed coating was sudden. |
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