Preparation And Performance Of Fe-Based Wear-Resistant And Corrosion-Resistant Coatings Formed By Supersonic Arc Spray Technology

In this paper,three kinds of coatings were prepared by supersonic arc sprayingtechnology.According to the composition of the core of wires,the coatings were302Acoating,high chromium coating and chromium carbide coating.The surface and crosssection morphology and microstructural characteristics of three coatings were observedby scanning electron microscopy(SEM), and Energy Dispersive Spectrometer (EDS) wereused to analyse the distributions of the chemical elements and compositions of threecoatings.Phase compositions of three coatings were analyzed by X-raydiffraction(XRD).In addition, microhardness, wear resistance, corrosion resistance, hightemperature oxidation and thermal shock behaviors of the coatings were tested withmicro-hardness tester, wear tester and electrochemical workstation and resistancefurnace.Then the wear and friction property, electrochemical corrosion mechanism andhigh temperature oxidation behavior of the coatings were studied and compared.According to the SEM images of three coatings,the microstructure of three coatingswere well-distributed and compact.Most of the particles’ deformation were sufficient toform flakes,some metallic particles did not deform enough.In the coatings few obviousdefects existed,but some pores could be observed,while the porosity of the three coatingswere less than10%. Most of pores often existed between flakes or near undeformedparticles.The microhardnesses were tested on the cross section,the average values werecalculated.The tested results indicated that302A coating had the highest hardnessvalues,it’s about five times of the matrix’s.Chromium carbide coating’s microhardnesswas smaller than the302A coating,which was four times as the matrix’s.And highchromium coating had the lowest value among the three kind of coatings,about two timesas the matrix’s.The results of sliding wear tests(block-on-ring confguration) with lubricationdemonstrated that302A coating had the best wear-resisting performance,whose loss ofweight was just10~19%compared with the losses of the matrix.The loss of weight ofchromium carbide coating and high chromium coating were14~20%and28~33% respectively.The wear mechanisms of the three coatings were abrasive wear. Abrasivewear mechanism of302A coating were a blend of microscopic cutting, plough ditch,plastic deformation fatigue and microscopic rupture (flake off) wear.Abrasive wearmechanism of high chromium coating were a blend of serious ploughing and adhesivewear.Abrasive wear mechanism of chromium carbide coating was microscopic cutting.By testing the polarization curves in3.5%NaCl solution, the conclusions indicatedthat the high chromium coating performed best because of the large mount of chromiumcontained in the coating.In the chromium carbide coating,the existences of chromiumcarbide and Ni would help with improving the corrosion resistance.The302A coating hadthe same corrosion potential,-0.65V, as the matrix,while the chromium carbide’scorrosion potential improved from-0.65V to-0.61V,the high chromium coating’scorrosion potential improved-0.65V to-0.58V.The oxidation behaviors of three coating under temperature at600℃after120hourswere investigated. The test results indicated that three coating could provide betteroxidation protection for substrate. Judged by the gaining weight and the oxidationmorphology,the302A coating and high chromium coating performed better than the highchromium coating in oxidation resistance.Compared with the matrix,three coatingsshowed better high temperature oxidation resistance.By taking the thermal shock tests at600℃and800℃,the coatings with a interlayed bond coating revealed better anti-thermalshock ability than the coatings without a bond coating.