Fabrication,Anti-corrosion And Wear-resistance Properties Of Fe-based Amorphous Coatings By HVOF

Using the spray materials of FeCoCrMoCBY amorphous powders with industrial raw materials,the Fe-based amorphous coatings were fabricated by high velocity oxy-fuel spraying.The effect of process parameters on microstructure and properties of the coatings was investigated by X-ray diffraction,differential scanning calorimetry,scanning electron microscope and vickers microhardness tester,respectively.The anti-corrosion of the coatings and 316 L stainless steel was studied by potentiodynamic polarization test in HCl solution.And the corrosive process of the coating was studied in the different corrosive medium,solution concentration and enviro nment temperature.The wear-resisting of the coating was analyzed with the different load and rotational speed by abrasion tester.The results show that :The FeCoCrMoCBY amorphous coatings exhibit good adhesion with substrate and typical lamellar structure,and there are interface layer about 20 nm of amorphous between the deformation layers.The coatings have high amorphous content,thus exhibit more excellent corrosion resistance than 316 L stainless steel.With the increase of kerosene content,the density of coating increase,its amorphous content and microhardness firstly increase and than decrease in the range of test parameters,and the average microhardness exceeds 1017 HV.With the decrease of spraying speed,the coating porosity decrease,but its amorphous content decline from 90% to 32%,the precipitating crystalline phase,such as ?-Fe,FeO and Fe3 C,and the microhardness clearly decline.With the size of powders decrease,the density of coating increase,but it is easier to crystallize.When the spraying distance is shorter,the coating porosity increase,but its amorphous phase get more stable.When the rate of feedstock powders is lower,the coating porosity decrease and distributed homogeneously.The FeCoCrMoCBY amorphous coatings have more excellent anti-corrosion than 316 L stainless steel in the HCl and NaCl,specifically,which exhibit obviously passive characteristics and lower self-corrosive current density and higher self-corrosive potential,and its potential of the passive film rupturing approaches 1.0 V.However,its passive film ruptures and accelerates the corrosive rate in the H2SO4 and NaOH because of the trans-passive phenomenon.With the increase of corrosive solution concentration or temperature,corrosive current density of the coating increase,which lead to decline the anti-corrosion.The place of initiate corrosion in order is the hole,the interface layer including much oxide,and then the particle surface being oxidied or crystallized.Wider of the interface layer gets or higher of the spraying temperature arrives,the greater of tendency to occur the zone of poor Cr and then corrosion.The FeCoCrMoCBY amorphous coatings have more excellent wear-resistance,and have lower friction coefficient of 0.15~0.23 than 316 L of 0.28.When the load belows 5 N,wear mechanism mainly presents the fatigue and oxidation wear.However,when the load exceeds 10 N,the friction coefficient of the coating reduces overall,and the wear loss increases,which results in wear mechanism turn into oxidation and abrasive wear.With the increasing of the rotational speed and the friction coefficient,the relative width of grinding crack firstly increase and then decrease.The wear surface is higher than the original profile,and presents a kind of rough and cataphracted morphology.When the rotational speed increases from 300 r/min to 600 r/min,the wear mechanism is the combination of fatigue wear and oxidation wear,which turns into the combination of fatigue,oxidation and adhesive wear.