Investigating the correlation between parameters of deep cryogenic treatment, microstructure and mechanical properties of Vanadis 4 Extra tool steel using cyclic indentation testing

Optimizing deep cryogenic treatments (DCT) for tool steels is challenging due to the complex interplay between process parameters, treatment sequences, and the resulting mechanical properties. Consequently, time-efficient methods to characterize the mechanical properties of cryogenically treated materials are required. In this study, the short-time method PhyBaL CHT , which is based on cyclic indentation testing (CIT), was used to systematically evaluate the influence of cryogenic processes on the cyclic deformation behavior and hardness of the tool steel Vanadis 4 Extra. For this purpose, various process sequences comprising quenching, static DCT or cyclic DCT (CDCT), and tempering ( T T : 450 °C; 500 °C; 550 °C) were investigated. The results obtained in CIT demonstrate that the tempering temperature is crucial for the mechanical properties and interacts strongly with the cryogenic process: applying cryogenic steps before rather than after tempering yields opposite changes in hardness and cyclic deformation behavior for T T = 450 °C compared to T T = 550 °C. Furthermore, it is shown that CDCT yields similar mechanical properties to static DCT while requiring considerably shorter processing time. Overall, the results show that PhyBaL CHT resolves small differences in the mechanical properties of cryogenically treated tool steels and support the applicability of PhyBaL CHT for comparative characterizations of these materials. These differences are discussed in relation to the microstructural changes observed by scanning electron microscopy and X-ray diffraction.