Influence of the nitriding process on the durability of tools used in the production of automotive forgings in industrial hot die forging processes on hammers

This work concerns the analysis of the application of the nitriding process to forging dies used for the production of automative forgings on a hammer. The subject technological process concerns the production of forgings of a ring section made of AISI 304 stainless steel. The subject process is carried out on a LASCO HOU-160 forging hammer with a power of 16 kJ, in two operations, on the blocking impression and then on the finishing impression. In order to assess the influence of the nitriding process on the durability of tools, operational tests are carried out for three sets of tools after thermochemical treatment under real industrial conditions and then confronted with the results for standard tools (without a nitrided layer). The comprehensive studies carried out, including macroscopic analyses combined with scanning, numerical modeling, and microstructural tests for both standard tools and after nitriding, show a decrease in the durability of forging tools as a result of the use of nitriding in relation to the previous technology. It should also be considered that the process was carried out on hammers, for very thin forgings. Then, there are very high dynamic loads, which can lead to cracking of hard nitriding layers.