Microstructure And Wear Resistance Of TiB₂-TiC Composite Coatings Prepared By Plasma Cladding

In mines,machinery,metallurgy and other fields,a large number of key components are invalidated because of serious wear.Strengthening the surface of the components and forming high performance wear-resistant coatings on the surface is an important way to prolong the service life and improve the use performance,which can save the cost effectively.TiB2-TiC based metal matrix composites have excellent high temperature resistance,corrosion resistance and wear resistance.They have high quality of temperature resistant,wear resistant and corrosion resistant.It has broad application prospects in industrial production.Plasma beam has high energy density,high heating efficiency,simple equipment and technology,which is suitable for large-scale industrial applications.Under the support of the National 863 Project(Preparation and characterization of wear resistant composite coatings by plasma spray deposition,2015 AA034404).A kind of composite ceramic coatings with TiB2 and TiC as strengthening phases prepared on the surface of Q235 steel by plasma cladding which using Ti,B4C,Fe55 and MoS2 powders as precursor.The evolution process of microstructure in TiB2-TiC composite coating was discussed.The effects of Ti+B4C content,scanning speed and different content of MoS2 on the morphology,size and distribution of the enhanced phase were studied,and the wear mechanism was discussed.The main contents are as follows:1)Using Ti,B4C and Fe55 powders as precursor,Prepared composite coatings on the surface of Q235 by plasma cladding.The microstructure of the cladding layer is mainly composed of TiB2,TiC,?-Fe,Fe3(C,B)and(Fe,Cr)7C3.The TiB2 is polygon and rectangle,and TiC is irregular lump.With the increase of Ti+B4C content,the size of TiB2 and TiC becomes larger.The hardness of plasma cladding coating increases gradually which up to 970 HVo.5 and it is about 5.1 times of the Q235 substrate.When the content of Ti+B4C is increased to 30wt%,the wear resistance of the coatings is better and it is about 7 times of that of the Q235 substrate.The wear mode of the TiB2-TiC cladding coatings is mainly abrasive wear and peeling wear.2)When the cladding speed is changed,the size of TiB2 and TiC increases gradually with the decrease of the cladding speed,and the defects of the ceramic phase are increasing gradually The average mierohardness of the cladding eoatings is between 600 HVo.s-850 HV0.5 which is 3-4 times of the Q235 substrate.With the decrease of the coatings speed,the hardness and the wear resistance of the coatings decreases gradually.When the speed is 300 mm/min,the wear resistance of the coatings is better,which is about 7 times of the Q235 substrate.3)Plasma cladding coating was prepared by Ti,B4C,Fe55 and different contents of MoS2.The cladding coatings mainly composed of TiB2,TiC,TiS,Ti2CS,?-Fe,Fe3(C,B)and(Fe,Cr)7C3.With the increase addition of MoS2,the diffraction peak intensity of TiS and ThCS is enhanced.The microhardness of the plasma cladding coating decreases with the increase of the amount of MoS2 added,which is due to the low hardness of Ti2CS,but the overall hardness of the coating is much higher than that of the Q235 substrate.and the hardness of coatings decreased gradually along with the depth direction.With the increase addition of MoS2,the friction coefficient of the coating decreased gradually.When the addition of MoS2 reach to 10%,the wear resistance of the coatings is better,and the wear volume is about 1/2 of the coatings with no MoS2.When MoS2 is add to 15%,the wear resistance decreased due to the decrease of coating strength.