A retrospection of the effect of nitriding processes on the AISI H13 tool steel

AISI H13 hot-work die steel has proved to be a promising material for hot work die making. Still, there are challenges in using H13 steel, with an impressive advancement having been made in the recent past. The purpose of this article is to build up a comprehension of how mechanical and tribological properties of current altered hot working die tool AISI H13 steel are affected by surface hardening techniques at elevated temperature. In this article, emphasis was made on how the combination of nitriding methods such as gas, salt, plasma with austenitizing and tempering temperature influences the material properties. It has been reported in various articles that nitriding between 450°C and 550°C with moderate nitriding time and high hardness by PIII nitriding, could be achieved by avoiding compound layers by minimising nitrogen potential with better adhesion of diffusion layers. However, with low nitriding temperature, problem of corrosion occurs due to the formation of a thin non-compact layer having thickness < 1 µm of Ɛ- Fe2-3N and γ´ -Fe4N. Also, wear and hardness of the nitrided layer increase 4 times under varying conditions, but, as we move towards the core reduction in hardness was recorded. It is concluded that prior to plasma nitriding of preheated AISI H13 steel, austenitizing must be done to incorporate properties like resistance to thermal fatigue cracking and sliding wear at elevated temperatures. It is also recommended that if hot work dies are plasma nitrided prior to coating, then their life can be increased, such as the in case of aluminium extrusion dies.