Arc additive manufacturing of gradient hot forging die with shaped waterways

Under the working environment of high temperature and strong load impact, hot forging die is prone to failure which reduces the service life of die. Using arc additive manufacturing in the die cavity, a gradient material hot forging die with high precision, superior performance, and conformal cooling channels is developed. This improves the toughness of the die cavity and reduces the working temperature, thereby forming an isothermal field, which is an effective method to enhance the lifespan of the hot forging die. Three kinds of gradient flux-cored wires are designed for the surface of 5CrNiMo steel, and the microstructure and mechanical properties between gradient interfaces were studied. Based on the spatial curved structure of shaped waterways in the hot forging die cavity, a study was conducted on the strategy of partitioned forming for the manufacturing of the die with shaped waterways. In order to avoid interference with the arc gun, the hot forging die is divided into four regions, namely the transition region, upper, middle, and lower region, based on a combination of cavity depth and internal U-shaped and quadrilateral structures. The results show that the developed flux-cored wires have good moldability with straight sides of deposited metal under different process parameters and flat surface without cracks, pores and other defects. Under the same working conditions, the life of hot forging die formed by the gradient materials is more than multiple times that of the single material hot forging die, and the temperature gradient field of the shaped waterway die is 7 ℃/cm smaller than that of traditional straight waterway.