High temperature oxidation resistance and microstructure change of aluminized coating on copper substrate
(School of Materials Engineering, Nanjing Institute of Technology, Nanjing 211167, China)
Abstract: The outermost coating with single phase Ni2Al3 was obtained on copper surface by electrodepositing nickel followed by slurry pack aluminizing at 800 °C for 12 h. The oxidation resistance and microstructure of the coating oxidized in ambient air at 1000 °C for 25-250 h were investigated using SEM, X-ray diffraction and optical microscope methods. The results show that the copper with single phase Ni2Al3 coating possesses the best high temperature oxidation resistance, and the mass gain of the coating is 1/15 that of pure copper and 1/2 that of nickel coating, respectively. The specimen surface after being oxidized for 25 h still comprises Ni2Al3 phase. However, when the time of oxidizing treatment increases to 50 h, the NiAl phase is formed. It is also found that the Ni2Al3 phase completely turns into NiAl phase after oxidizing treatment for 100 h and above. The NiAl coating shows excellent high temperature oxidation resistance when oxidation time is 250 h.
Key words: copper; Ni2Al3 coating; high temperature oxidation resistance; NiAl phase; pack aluminizing