Adaptive nanolaminate coating by atomic layer deposition

Atomic layer deposition (ALD) was used to deposit ZnO/Al2O3/V2O5 nanolaminate coatings to demonstrate a coating system with temperature adaptive frictional behaviour. The nanolaminate coating exhibited excellent conformity and crack-free coating of thickness 110 nm over Inconel 718 substrate. The ALD trilayer coating showed a hardness and elastic modulus of 12 GPa and 193 GPa, respectively. High-temperature tribology of the nanolaminate trilayer was tested against steel ball in dry sliding condition at 25 degrees C (room temperature, RT), 200 degrees C, 300 degrees C, and 400 degrees C. It was found that the nanolaminate coating showed a low coefficient of friction (COF) and wear rate at RT and 300 degrees C. The trilayer coating was found intact and stable at all temperatures during the friction tests. The adaptability of nanolaminate coating with the temperature was verified by performing the cyclic friction test at 300 degrees C and RT. The low COF and wear rate had been attributed to the (100) and (002) basal plane sliding of ZnO top layer, and the interlayer sliding of weakly bonded planes parallel to (001) plane in V2O5 bottom layer. Furthermore, even after the removal of ZnO coating during the tribotest, the bottom V2O5 layer coating stabilized the COF and wear rate at RT and 300 degrees C.