Influence of niobium ion implantation on the microstructure and tribological properties of TiAlN coatings

To improve the performance of TiAIN coatings used for cutting tools, the metal vacuum vapor arc (MEVVA) ion implantation was used to enhance hardness and wear resistance of the coatings. In this paper, TiAIN coatings were deposited on the substrates of cemented carbide (WC-TiC-Co) with magnetic filtered arc ion plating(MFAIP) method and implanted with niobium ions at 40 kV with the doses of 1 x 10(17) and 5 x 10(17) ions/cm(2) by MEVVA ion source. HRTEM, EDS, and GIXRD tests are used to investigate the effects exerted by ion implantation doses on the microstructure, microhardness and tribological properties of the TiAlN coatings. EDS results showed that the projected range of Nb-implanted TlAlN coatings was about 130 nm and corresponded well with the results calculated by a TRIM code (112.5 +/- 19 nm). Amorphous and nanocrystalline composite structure with a thickness of about 50 nm was found in the surface layer of Nb-implanted coatings by HRTEM, and the nanocrystalline with a size of about 5-10 nm was distributed in amorphous structure. The analysis of GIXRD showed that after Nb ion implantation, the TiAIN peaks shifted toward the high 20 angle side and became broad as a result of lattice distortion and a new phase of NbN was formed. The microhardness of the coatings after Nb ion implantation increased remarkably, whereas the friction coefficient had no significant improvement. Wear loss and wear area of TiAIN coatings were significantly reduced with increasing dose of implanted Nb ion. (C) 2012 Elsevier B.V. All rights reserved.