Analyzing the influence of a deep cryogenic treatment on the mechanical properties of blanking tools by using the short-time method PhyBaLCHT

Deep cryogenic treatment (DCT) is a promising post-process for increasing the service lifetime of highly loaded tools. However, the process parameters as well as the position of DCT during thermal post-processing have to be adapted on the materials used, leading to high experimental effort, costs and time to optimize and validate this kind of thermal treatment. Therefore, efficient methods to analyze the mechanical properties of materials treated with DCT are of great industrial and scientific interest. In this context, the short-time method PhyBaLCHT, which is based on instrumented cyclic indentation tests, is a promising approach, as it enables a rapid determination of the cyclic deformation behavior and hardness of a material. Consequently, in the presented work different material conditions of the thermally treated tool steels 1.2379 (X155CrVMo12-1; AISI D2) and Vanadis 4E (140CrMoVMnSi19-35-37) were characterized by using cyclic indentation testing. The different conditions were realized by performing different sequences of thermal post-processing, containing quenching, tempering and DCT. The results obtained in cyclic indentation tests show for both materials slightly lower hardness but significantly higher cyclic plasticity of the material conditions treated with DCT antecedent to the tempering process compared to conventionally quenched and tempered material. In additionally performed blanking tests, this further results in an increased wear resistance of cryogenically treated conditions. Because of the higher cyclic plasticity, the reduction of local stress intensities at the cutting edges caused by plastic deformation is more pronounced for the cryogenically treated tools, which results in decreased wear rate as well as less pronounced breaking of the cutting edges. Consequently, the presented results demonstrate that the PhyBaLCHT method is a powerful means to characterize the mechanical properties of cryogenically treated materials and enables an estimation of the wear characteristics of highly loaded tools.