Fabrication and characterization of in-situ duplex plasma-treated nanocrystalline Ti/AlTiN coatings

Plasma nitriding and plasma-assisted PVD duplex treatment was adopted to improve the load-bearing capacity, fatigue resistance and adhesion of the AlTiN coating. Ion etch-cleaning was applied for better adhesion before plasma nitriding. After plasma nitriding Ti interlayer was in-situ deposited by high power impulse magnetron sputtering (HIPIMS), followed by the AITiN coating through in-situ deposition by advanced plasma-assisted arc (APA-Arc). The microstructure and properties of the duplex-treated coating were carefully characterized and analyzed. The results show that the thicknesses of the nitriding zone, the gamma'-Fe4N compound layer, the Ti interlayer and the AlTiN top layer with nanocrystalline microstructures are about 60 mu m, 2-3 mu m(,) 100 nm and 6.1 mu m, respectively. The nitriding rate is about 30 mu m/h and the AlTiN coating deposition rate reaches 6.1 mu m/h. The interfacial adhesion of the Ti/AlTiN coating is well enhanced by ion etch-cleaning and a Ti interlayer, and the load-bearing capacity is also improved by duplex treatment. In addition, the instinct hardness of the Ti/AlTiN coating reaches 3368HV(0.05) while the wear rate coefficient of 5.394 x 10(-8) mm(-3)/Nm is sufficiently low. The Ti/AlTiN coating, which possesses a high corrosion potential (E-corr = - 104.6 mV) and a low corrosion current density ( i(corr) = 4.769 lambda A/cm(2)), shows highly protective efficiency to the substrate. (C) 2016 Elsevier Ltd and Techna Group S.r.l. All rights reserved.