Effect of process variables on gas nitriding of H13 tool steel with controlled nitriding potential

AISI H13, a typical material used for hot extrusion dies, is gas nitrided using automated two-stage controlled nitriding process with the aim to evaluate the controlled nitriding process on nitride layer formation in terms of morphology, case depth and hardness variation across the nitride layer. A sequentially coupled thermal-diffusion analysis of actual nitriding cycle is performed numerically using finite element code, ABAQUS. The results show that the growth of nitride layer and the nitrogen concentration distribution in the diffusion zone can be accurately predicted numerically in close agreement with experimental results. The influence of nitriding time, temperature and potential is studied and it is found that these parameters significantly affect the nitride layer formation in terms of nitrogen concentration and hardness variation as a function of nitride case depth.