Hardness Assessment Considering Nitrided Layers Based on Tempering Tests for Numerical Wear Prediction for Forging Processes

• Published in: Materials Vol. 15; no. 20; p. 7105
• Main Authors: Behrens, Bernd-Arno, Brunotte, Kai, Wester, Hendrik, Lorenz, Uwe, Müller, Felix
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.10.2022; MDPI
• Subjects: Analysis; Annealing; Archard model; Forging; Hardness; hardness modeling; Investigations; Laboratories; Mathematical models; Mechanical properties; Metalworking machinery; nitrided layer; Nitriding; Nitrogen; Numerical prediction; Plasma; Production planning; Steel; Surface layers; Tempering; tool life; Tool steels; Tool wear; Tool-steel; wear calculation; Germany
• ISSN: 1996-1944; 1996-1944
• DOI: 10.3390/ma15207105

The nitriding of forging tools is an industrially established standard used to increase the hardness of the tool surface layer and reduce wear. However, this modification of the tool surface layer, as well as the microstructural changes that occur during this operation due to the thermo-mechanical load, cannot be considered during wear calculations with the widely used Archard wear model in the context of FE simulations. Based on previous work, this study further develops two tempering tests for the investigation of the hardness evolution of two nitride profiles based on H11 tool steel. Here, significant tempering effects could be observed depending on temperature, mechanical stress superposition and time. The results are used for setting up a new material model that is implemented in an existing numerical wear model. The validation is carried out in two laboratory forging test series. The evaluation shows that the hardness development in terms of tempering effects of a nitrided forging tool can be numerically predicted, especially for high forging cycles. However, due to the unexpected occurrence of adhesion effects, only limited applicability of the wear prediction then carried out is achieved.