FE-based development of highly wear resistant hot working tools by alloy modification in combination with a process- and material adapted nitriding layer

• Applicants: Professor Dr.-Ing. Bernd-Arno Behrens; Professor Dr.-Ing. Hans Jürgen Maier, since 10/2014
• Subject Area: Primary Shaping and Reshaping Technology, Additive Manufacturing
• Term: from 2014 to 2017
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 260050454

Within the applied research project adapted hot working tools for the special requirements in hot forming processes will be developed by realizing an adapted alloy modification in combination with a process- and material adapted nitriding layer. By controlled process guiding during the nitriding process defined nitriding layers will be adjusted to investigate the influence of the nitriding depth and hardness gradient on the tool performance. To adjust defined and reproducible nitrding layers the plasma nitriding process will be used. The alloy modification bases on previous research works. Here, a standard hot working steel will be alloyed with additional amounts of manganese to increase the effect of the cyclic edge layer hardening by lowering the austenitic temperature Ac1b.The time- and temperature depending hardness profile of forging tools has a significant influence on the wear resistance. The surface temperature of the dies increases highly during the forming process of raw parts with a temperature of up to 1200 °C. The surface temperature plays a decisive role on the contribution of thermal energy into the tools. An experimental measurement of the surface temperature is not possible due to the high working loads in the contact zone. Therefore, alternative experimental and numerical methods will be used within the project for a holistically consideration of the edge layer phenomena. To characterize the hardening behavior of the tools time and temperature depending hardness profiles will be identified by dilatometer tests. To use the real and process depending temperature profiles for this test, a numerical and experimental determination of the temperature profile in the edge layer of the tools will be performed. For this purpose, thermocouple elements will be positioned near the surface zones of the dies with varying depth and the temperature profiles as a result of the forging process will be determined. With this data the numerically calculated temperature profiles will be validated and the development of the surface temperature will be calculated. The surface temperature will be used as an input value for the measurements in the dilatometer. After the dilatometer tests, the serial forging tests will be conducted on an industry related automated forging line. Analogous to the cycle times in the dilatometer tests wear measurements will be performed after the forging tests. This approach allows the investigation of the transferability of the experimentally investigated hardness profile with the wear rates measured out of the serial forging tests. The data gained within the project will be used, to expand an existing FE-based wear model considering the time- and temperature depending hardness gradient.

• DFG Programme: Research Grants
• Ehemaliger Antragsteller: Professor Dr.-Ing. Friedrich-Wilhelm Bach, until 10/2014 (†)