Enhancement of high-temperature oxidation resistance and mechanical properties of Ni3Al thin films by inserting ultrathin Cr layers

Ni3Al thin films and Ni3Al/Cr multilayer films with a chemically ordered intermetallic Ni3Al phase were deposited on NO6625 alloy substrates by magnetron sputtering at 400 °C. Compared with the single layers, the multilayer samples show superior high-temperature oxidation resistance and mechanical properties. Both of the samples can prevent the substrate from being drastic oxidized even at 1100 °C. Their oxidation kinetics was found to follow the logarithmic law at 900 °C and be converted to the parabolic law at 1000 °C and 1100 °C. The oxidation rate can be reduced by one order of magnitude after inserting the Cr ultrathin layer. Nanoindentation measurements revealed that the hardness was decreased from 8.4 GPa to 8.0 GPa while the elastic modulus was increased from 191.4 GPa to 219.2 GPa. Furthermore, nano-scratch test indicated that the multilayer exhibited improved scratch toughness than that of the Ni3Al thin film.