Effects of slurry pack cementation temperature on microstructure and wear resistance of Ti-Al co-deposited coating on copper plated nickel layer
(School of Materials Engineering, Nanjing Institute of Technology, Nanjing 211167, China)
Abstract: In order to improve the wear resistance properties of copper substrate, a layer of electroplated nickel was firstly deposited on copper substrate, subsequently these electroplated specimens were treated by slurry pack cementation process with a slurry pack cementation mixture composed of TiO2 as titanizing source, pure Al powder as aluminzing source and also a reducer for titanizing, an activator of NH4Cl and albumen (egg white) as cohesive agent. The Ti-Al coating was fabricated on the surface of electro-deposited nickel layer on copper matrix followed by the slurry pack cementation process. The effects of slurry pack cementation temperature on the microstructures and wear resistance of Ti-Al coating were studied. The results show that the microstructure of the coating changed from NiAl+Ni3(Ti,Al) to NiAl +Ni3(Ti,Al)+Ni4Ti3 to Ni4Ti3+NiAl, and to NiAl+Ni3(Ti,Al)+NiTi with slurry pack cementation temperature ranging from 800 °C to 950 °C in 12 h. The friction coefficient of Ti-Al coating decreased and the hardness increased with increasing the slurry pack cementation temperature. The minimum friction coefficient was 1/3 and the minimum hardness was 5 times larger than that of pure copper.
Key words: Ti-Al coating; Ni-Ti intermetallic compound; Ni-Al intermetallic compound; slurry pack cementation temperature; wear resistance