Microstructure and properties of nano-Al2O3 particle reinforced Ni–Cr–Mo–Cu composite alloying layer

In order to improve the corrosion and wear resistance of 316L stainless steel (SS) in engineering application, Ni–Cr–Mo–Cu composite alloying layer reinforced by the nano-Al2O3 particles was prepared by double glow plasma alloying on 316L stainless steel surface, where Ni/nano-Al2O3 was firstly predeposited by brush plating. The composition and microstructure of composite alloying layer were analyzed by means of SEM, TEM and XRD. The results indicated that under alloying temperature (1000 °C) condition, the added nano-Al2O3 was partially dissolved into γ-Ni based solution matrix, resulting in γ-prime (Ni3Al) phase precipitation. The γ-prime phase grew in a unique crystallographic orientation relationship with the γ-Ni based solution matrix. This crystallographic relationship can be described as (1 1 1)γ-Ni//(1 1 1)γ′-Ni3Al. The corrosion resistance of the composite alloying layer was investigated electrochemically in 3.5% NaCl solution and in 5% HCl solution, and 100-h immersion tests in a 20% HCl solution. Compared with Ni–Cr–Mo–Cu alloying layer, nano-Al2O3 particles and in situ synthesized γ-prime phase slightly decrease the corrosion resistance of the alloying layer. The dry wear test results showed that the wear weight loss of composite alloying layer was 45% and 65% less than that of 316L stainless steel and Ni–Cr–Mo–Cu alloying layer, respectively.