Abstract
Hard coatings on tools are very effective for wear resistance and the prevention of scuffing in forging; thus, many new coatings are developed yearly. The function of hard coatings in the reduction of friction has markedly improved recently; however, a method for its effective evaluation under practical forging conditions has not yet been developed. In this research work, we discussed the effectivity of the taper cup test, which we developed, as a new evaluation method. The taper cup test estimates the friction coefficient under a high surface expansion ratio, which is almost the same level to as those for mass-produced forging components. In the case of using no lubricant, diamond-like carbon (DLC) has a much lower friction coefficient than TiAlN and TiN. In the case of using one-liquid lubricant, friction coefficient is affected by surface roughness depending on the type of hard coating. In addition, continuous forging smoothened the surface, there by decreasing friction coefficient.
