Improved micro drill bit tool life using nano-scale SiC/ Ni electroplating

Abstract

SiC/Ni composite layers were coated onto WC-Co plates to strengthen micro drill bits where the micro drill bits were machined from WC-Co plates. The composite layers were formed by direct current (DC) electrodeposition in a Watts-type bath, and two SiC concentrations were used to coat the WC-Co plates. The coating layer was optimized by evaluating the hardness and the friction coefficient. With 10 g/l of SiC, some nanoparticles agglomerated and were embedded into the coating layer; moreover, the composite coating layer was not uniform. Compared to the 10 g/l SiC coating, the nanoparticles were well dispersed and the coating was harder using 5 g/l of SiC. After electroplating the micro drill bits, a positioning accuracy test was conducted to assess processing capability. The processing capability index was measured as 1.944 for the uncoated drill bit, 2.110 for the 10 g/l SiC coating, and 2.717 for the 5 g/l SiC coating. Therefore, the micro drill bits coated with 5 g/l of SiC exhibited an optimized processing capability index. When using 100 µm-diameter drill bits, the composite coating layer, which is relatively thin, must be hard. Micro drill bits coated with 5 g/l of SiC had a 1 µm thick coating layer and an optimum processing capability.