Study On Preparation And Properties Of AT13/Fe-Based Amorphous Composite Coatings

Fe-based amorphous coatings have been extensively studied for their high strength,high hardness,good wear resistance and excellent corrosion resistance.However,the intrinsic brittleness and poor toughness of amorphous materials have severely restricted the engineering applications of amorphous coating.To improve this situation,AT13 ceramic particles were introduced into Fe Cr Mo CB amorphous coating.In this thesis,AT13/Fe-based amorphous composite coating were successfully prepared by plasma spraying process,and its microstructure and the effect of different AT13 content on the wear resistance and corrosion resistance of composite coating were investigated.The composite coatings were mainly composed of amorphous phase and?-Al₂O₃phase with well combined interface and high density.When the addition amount of AT13was 15 wt.%,the porosity of composite coating was the lowest,only 1.1%.The pure Fe-based amorphous coating has the highest hardness,and the hardness decreases slightly with the increasing of AT13 content.When the content of AT13 was 15 wt.%,the Webb modulus was the largest,which indicated that the microstructure distribution was relatively uniform and the mechanical property was the most stable.Under the same wear conditions,AT13/Fe-based amorphous composite coating has better wear resistance than the pure Fe-based amorphous coating.With the increasing of AT13 content,the friction coefficient decreased firstly and then increased slightly.The wear scar depth and wear rate of composite coating also showed a trend of decreasing first and increasing subsequently.When the content of AT13 was 15 wt.%,the composite coating had the lowest friction coefficient and wear rate,and the shallowest wear marks indicating that the wear resistance was optimal.The main wear mechanism of coatings was fatigue and oxidative wear under the low load.In addition,abrasive wear was accompanied under the high load.With the rised of the rotational speed,the wear scar depth and wear rate of the coating first increased and then decreased.When the rotational speed was 800 r/min,wear mechanism mainly presented a combination of fatigue wear,oxidative wear and adhesive wear.The potentiodynamic polarization test showed that the AT13/Fe-based amorphous composite coating exhibited good corrosion resistance in NaCl and H₂SO₄solutions.All coatings exhibited significant passivation behavior in 3.5 wt.%NaCl solution,and the breakdown potential of the passivation film(1.0 V)was much higher than that of 316L(0.4V).When the weight fraction of AT13 was 15 wt.%,the composite coating has the lowest corrosion current density and the highest corrosion potential.There was no significant difference in the corrosion resistance of all coatings in 0.5 mol/L H₂SO₄solution.In 10wt.%Na OH solution,the self-corrosion potential and over-passivation potential of amorphous coating were lower,and the corrosion rate was faster.The electrochemical performance parameters of the coating gradually decrease with the increase of AT13content,and the corrosion resistance is inferior to 316L stainless steel.The long-time immersion corrosion tests carried out on different coatings showed that the corrosion protection effect of coating was enhanced with the increase of the amount of AT13 added.The equivalent circuit of pure amorphous coating,5 wt.%and 10 wt.%AT13/Fe-based amorphous composite coating is R(Q(R(QR))).The efficiency circuit of 15wt.%and 20 wt.%AT13/Fe-based amorphous composite coating changes from(R(QR))to(R(Q(R(QR))))with the time continued.