Tribological properties of DLC films against aluminum and life of DLC coated die for ironing under dry condition

The pulse plasma CVD method with self bias discharge was applied to Diamond-Like Carbon (DLC) film coating of the the used under dry conditions. When DLC film was deposited on the the with deep hole, a uniform thick film was observed down the depth of the inner wall and the hardness and adhesive force of the film was adequate. Then, the tribological properties of DLC films against aluminum were studied with a ball-on-disk type tribometer under dry conditions. After repeated friction over a long period, the surfaces of DLC films derived from both methane and acetylene became smoother and the coefficient of friction for DLC film from methane in the initial sliding decreased. Lastly, the life of DLC film coated the was evaluated in ironing process of aluminum cup under dry conditions using an actual press machine. The die from methane gas showed significantly longer life than that from acetylene. It was inferred that longer life of the from methane was brought about by antiwear properties due to high hardness of DLC film during the continuous ironing process of aluminum cup.