Abstract
Tribo-properties of hard coated tools were evaluated under using cold-forming oils for steel by ball penetration test. Diamond-like carbon including Si (DLC-Si) is a special target of hard coatings for better properties of anti-galling and low friction, but it cannot show good performance under a dry condition for the severe test. Using pure mineral oil, VC, TiN and DLC-Si indicated large ball penetrating load. When oil containing phosphoric esters of 30% was applied, DLC-Si reduced the load by nearly 30% for VC and TiN, but some scratches were observed on the DLC-Si surface. Applying oil containing phosphoric esters and phosphoric acid, DLC-Si performed low friction without scratches on the surface. Also the load of DLC-Si was smaller than those of TiN and VC. The combination of DLC-Si and high performance oil was so effective.
