The Influence Of Diffusion Heat Treatment On Wear And Corrosion Resistance Of TC4 Alloy With Ni/Cu/Ni Coating

Titanium and titanium alloys are widely used in the transportation pipeline of petrochemical industry due to their excellent properties.However,in the joints of titanium alloy oil well pipes,due to its low thermal conductivity and poor wear resistance,it is easy to cause bonding so that affect the application of titanium alloy.At present,copper plating is a common way to improve the wear resistance and anti-stick performance.However,it is found that Cu has poor corrosion resistance and is easily corroded during service.Therefore,Ni/Cu/Ni composite coatings were prepared on the surface of TC4 titanium alloy.The effects of different diffusion heat treatment temperatures on the wear resistance and corrosion resistance of Ni/Cu/Ni composite coatings on TC4 titanium alloy were investigated.The wear resistance and corrosion resistance of Ni/Cu composite coating and Ni/Cu/Ni composite coating were compared.The results of the comparison of wear resistance and corrosion resistance of Ni/Cu composite coating and Ni/Cu/Ni composite plating are that the Ni/Cu/Ni composite plating has a slightly lower wear resistance than the Ni/Cu composite coating,but the corrosion resistance is better.After the Ni/Cu/Ni composite coating on the surface of TC4 titanium alloy was heat treated at different temperatures for 3 h,the Cu,Ni and Ti atoms in the coating diffused to different extents.With the increase of heat treatment temperature,Cu,Ni and Ti atoms migrated.As the amount increases,the transition layer due to diffusion also becomes thicker.In the heat treatment temperature range of 600?to 800?,the solid solution Cu_3.8Ni,intermetallic compounds Ni₃Ti,CuTi,Cu₂Ti,Ti₂Ni,Cu₄Ti₃ are successively formed in the Ni/Cu/Ni composite coating.Due to the different types and amounts of solid solution and intermetallic compound formed,as the heat treatment temperature increases,the surface roughness of the composite coating decreases and the surface microhardness increases.According to the friction and wear test results,the type and quantity of solid solution and intermetallic compound formed increase with the increase of heat treatment temperature,resulting in solid solution strengthening and dispersion strengthening.The Ti-Ni intermetallic compounds and the Ti-Cu intermetallics compound formed by the diffusion process have relatively high hardness.The combination of these compounds can effectively improve the hardness of the composite coating,thereby improving the wear resistance of the composite coating.The potentiodynamic polarization curves,electrochemical impedance spectroscopy and corrosion morphology obtained by electrochemical test and immersion corrosion test show that as the heat treatment temperature increases,the voids on the surface of the composite coating become smaller,which hinders the penetration of corrosive ions.At the same time,the corrosion resistance of the coating is improved due to an increase in the type and amount of poorly soluble intermetallic compounds.