Preparation And Properties Of SiC/Ta Composite Coatings Prepared On 4Cr13 Steel Surface

Martensitic stainless steel is widely used in industrial applications such as bearing structure,automobile component,hot-work die,turbine blade,oil and gas valve,and cutting tool of medical equipment,etc.due to its excellent mechanical properties,good wear resistance and corrosion resistance.However,when used in tribological and corrosive environment such as oil,chemical industry,shipbuilding and marine engineering,surface properties of martensitic stainless steel still face severe challenges.In this paper,Ta interlayers were prepared on the surface of 4Cr13 martensitic stainless steel using double glow plasma surface alloy technology(DGPSA)first;Then,H2 and TMS(Si(CH3)4)were passed into cavity as reaction gas to compound SiC coatings.SiC/Ta composite coatings were formed on the surface of 4Cr13 martens itic stainless steel,finally.Effects of concentratiosn of TMS and synthesis temperature of SiC on the microstructure,composition and structure of SiC/Ta composite coatings were analyzed.The hardness,adhesion strength,wear res istance and corrosion resistance were studied as well.Wear mechanisms and corrosion mechanism of SiC/Ta composite coatings prepared at different concentratiosn of TMS and different synthes is temperature of SiC were investigated.The results show as follows:(1)SiC/Ta composite coatings can be prepared on the surface of 4Cr13 martensitic stainless steel by the treatment of double glow plasma Ta-alloying and synthesis ing SiC.The thinkness of SiC/Ta composite coatings are 4.5-6 ?m,and the inter-diffus ion regions exsited at the SiC/Ta/substrate will cause a superior adherence.Along with the increase of the concentratiosn of TMS,defects such as cracks,holes appear gradually between SiC coatings and Ta interlayers.With the increase of synthesis temperature of SiC,SiC coatings gradually become loose from compact.(2)As concentratiosn of TMS increases,the content of SiC increased,while the total content of TaC and Ta2 C decrease in the surface of SiC coatings.With the increase of synthes is temperature of SiC,the total content of TaC and Ta2 C increases,SiC content relatively decreases in the surface of SiC coatings.(3)The adhesion strength between SiC/Ta composite coatings and substrates is high.And the hardness of surface is 1738 HV0.2,significantly higher than 4Cr13 subsrates'(279 HV0.2).The main reason for the raise is.the formation of carbide hard phase(SiC,TaC and Ta2C)in the SiC coating and the effective support of Ta interlayer.(4)The friction coefficient of 4Cr13 stainless steel after prepared SiC/Ta composite coatings is lower than that of the untreated stainless steel substrate,and the wear rate also was varying degrees of decline.Especially the wear rate of SiC/Ta composite coatings prepared using process parameters(H2/TMS flow rate = 10 sccm/1.0 sccm,synthesis temperature of SiC = 800 ?)is only 4 % of the untreated substrate,which shows good antifriction and wear res istance.Composition and hardness of SiC/Ta composite coatings are the main reasons for the wear resistance.(5)The polarization curve and impedance results show that the corrosion potential of the SiC/Ta composite coatings prepared by different process in 3.5 wt % NaCl are increased,and the corrosion current density is reduced.The impedance values are significantly greater than 4Cr13 substrate.All these illustrate SiC/Ta composite coatings can improve the corrosion resistance of 4Cr13 substrate.With the increase of concentratiosn of TMS,the performance of corrosion resistance becomes better;As synthesis temperature of SiC increases,corrosion resistant becomes better,then becomes worse.