Estimation of die service life in hot forging, considering lubricants and surface treatments

Abstract This study explains the effects of lubricant and surface treatment on hot forging die life. Thermal load and thermal softening, occurring when there is contact between the hotter billet and the cooler dies in hot forging, cause wear, thermal cracking and fatigue, and plastic deformation. Because the cooling effect and low friction are essential to the long life of dies, the proper selection of lubricant and surface treatment is very important in the hot forging process. The two main factors that decide the friction and heat transfer conditions are lubricant and surface treatment, which are directly related to the friction factor and the surface heat transfer coefficient. Experiments were performed to obtain the friction factors and surface heat transfer coefficients for different lubricants and surface treatments. For lubrication, oil-base and water-base graphite lubricants were used, and ion nitride and carbon nitride were used as surface treatment conditions. The effects of lubricant and surface treatment on die service life were expressed as the possible maximum production quantity. The new techniques developed in this study for estimating die service life can be used to develop more feasible ways to improve die service life in the hot forging process.