Metallurgical characteristics and machining performance of nanostructured TNN-coated tungsten carbide tool

The effect of depositing Nb-rich Ti Nb N coatings on the metallurgical characteristics and machining performance of tungsten carbide tools is investigated. The direct current reactive magnetron sputter deposited Ti Nb N thin film was crystalline in the as-deposited state. The surface of the film is characterized by a dense granular structure with very few voids and lower roughness than the pristine tungsten carbide surface. Nanoindentation studies revealed that the Ti Nb N coating enhanced the hardness and Young's modulus of the tungsten carbide tool to 35 GPa and 703 GPa, respectively, as compared to 20 GPa and 550 GPa respectively, for the uncoated tool. Scratch tests showed that the Ti Nb N coating increased the adhesion strength on the tungsten carbide tool. Similarly, the tool wear, surface roughness and cutting force in turning an EN24 alloy steel component displayed significant improvement due to the Ti Nb N coating. The minimum surface roughness, minimum tool flank wear and minimum cutting forces were predicted for Ti Nb N coated tools based on the Taguchi experimental design.