Microstructure, tribological and cutting performance of Ti-DLC/α-C:H multilayer film on cemented carbide

Ti-DLC/α-C:H multilayer film was synthesized on cemented carbide by alternating Ti doped DLC and hydrogenated amorphous carbon through a combination of mid-frequency reactive magnetron sputtering and linear ion source technology. The microstructure, adhesion, toughness and wear behavior as well as the cutting performance were studied by the means of AFM, Raman, SEM, scratch test, ball-on-disk friction test and dry turning experiment. The results showed that the smooth and uniform surface morphology of Ti-DLC/α-C:H was the complementary results of each monolayer film, with decreasing sp3 content and rising sp2 graphite cluster compared with the monolayer α-C:H. The multilayer film displayed the adhesion of 110 N and toughness of 2980 N2, both of which were superior to each monolayer film. The friction coefficient of Ti-DLC/α-C:H was 0.075 with wear rate of 4.82 × 10−8 mm3/Nm decreasing by an order of magnitude compared with the monolayer α-C:H. The Ti-DLC/α-C:H coated YG8 cemented carbide cutting tool exhibited the longest service life of 25 min which was 1.4 times longer than the α-C:H coated and 1.7 times than the non-coated. The abrasive wear was the primary flank wear form of both non-coated and DLC coated tools with no distinct oxidative wear or diffusion wear.