The main phenomena limiting the useful lifetime of tools are frictional wear and thermal fatigue in case of hot-work tools. The cost of wear is very high and comprises not only a shorter working life due to premature failure, but also downtime required to replace the worn part or tool. Gas nitriding increases the surface hardness, reduces the coefficient of friction and creates at the surface a zone of high compressive stresses. Therefore it is well placed to improve the performance of cutting tools, but also in particular the performance of hot-work tools, such as forging and extrusion dies. Nitreg® nitriding with its precise control of surface concentration of nitrogen allows to obtain reproducible properties of treated parts, and so a consistently high performance.