Characterization of DLC thin film and evaluation of machining forces using coated inserts in turning of Al–Si alloys

A diamond-like carbon (DLC) thin film was deposited on cemented carbide cutting tool substrate by PECVD technique. In the first part of this research work a DLC thin film characterization was carried out. It was determined the following important characteristics: hydrogen content, nanohardness, Young modulus, friction coefficient and thickness of DLC coating. The DLC hydrogen content was situated between 10 and 20 at.% while the friction coefficient was 0.2. The DLC nanohardness and Young modulus were respectively 21 GPa and 205 GPa. The coating thickness was approximately 2.5 μm. The Ra roughness of the DLC coated surface was around 0.037 μm while the Ra roughness of the uncoated surface was around 0.030 μm. In the second part of this work cutting and feeding forces were evaluated when turning Al–Si alloys, using DLC coated and uncoated cemented carbide cutting tools. For the machining forces evaluation, a cutting speed of 450 m/min and cutting depth of 0.5 mm was used. The silicon content in the aluminum alloys was 12 wt.% and 16 wt.%. The feeding force was found to be higher when turning the aluminum alloy with 16 wt.% of silicon. The use of DLC coated cemented carbides tools reduces the feeding component of the machining forces, despite the silicon content in the aluminum alloy. However, the cutting force is not significantly affected either by the presence of a DLC thin film or by the silicon content in the aluminum alloy.