Novel performances of in situ plasma nitriding-PVD duplex-treated nanocrystalline TiN coatings

To improve the load-bearing capacity, hardness and adhesion strength of the TiN coatings, the in situ plasma nitriding-PVD duplex treatment was applied. The substrate was pretreated by bombardment with highly ionised Ar+, functioned as an ‘ionic abrasive blasting’ for better adhesion. The microstructure and properties of the duplex-treated TiN coatings were characterized and analysed. The results show that the thickness of the plasma nitriding zone and the nanocrystalline TiN coating are about 50 μm and 4.1 μm, respectively. Owing to the ion etch-cleaning process prior to the duplex treatment and the γ′-Fe4N phase formed in the compound layer, the adhesion strength level of the TiN coating reaches HF1. The indentation profile analysis reveals that the nitriding process effectively increases the load-bearing capacity. Meanwhile, the instinct hardness reaches 2166HV0.05 and the sufficiently low wear rate coefficient is 8.30 × 10−9 mm−3 Nm−1. Moreover, the duplex-treated TiN coating has significantly improved the corrosion resistance.