Enhanced adhesion of Ti-DLC films by Ti plasma etching treatment

The weak adhesion of DLC films has always been a poser and a hot issuer in the previous researches of DLC films. In order to satisfy the cutting requirement of difficult-to-cut materials and adapt to the severe service conditions, the methods to improve adhesion must be more efficient and convenient. The Ti plasma etching treatment was carried out by mid-frequency magnetron sputtering method. A Ti-DLC film was deposited on the etching treated surface. The film thickness and surface roughness were measured by stylus profiler. The surface morphology was characterized by SEM. The composition of DLC films was characterized by micro Raman spectrometer. The adhesion strength was measured by liner-loading scratch tester. The etching treatment removed a micro layer of 407nm on the substrate and increased the surface roughness from 3.50nm to 18.26nm. The surface WC crystals were exposed and partly broken by Ti plasma. Compared with the DLC films on non-treated surface and Ti layer, the DLC films on etching treated surface had the highest adhesion strength of 34.14N. The DLC films had similar compositions, so the adhesion difference came from the surface treatments instead of the inherent properties of DLC films. The Ti plasma etching treatment removed a micro layer of substrate material and it brought higher chemical activity, which contributed to improve the adhesion. The increased roughness deferred the continuous spalling of DLC film in the scratch test. The changes worked together to improve the adhesion strength of DLC films.