“…Jawahir et al [2], following the recommendations of research and standards organizations, indicated three limits (−150 • C, −153 • C, and −180 • C) below which cryogenic temperatures can be defined. The authors noted that −180 • C is a logical limit since the boiling points of the stable gases helium, nitrogen, neon, hydrogen, and oxygen are below −180 • C. Analyzing the processing of steels under negative temperature conditions, Diekman [4] applied the concepts of cold treating and cryogenic treatment, stating that the optimal temperature for cold treating is −84 • C, whereas typical CrT processes consist of a slow cool-down from ambient temperature to approximately −193 • C. In a comprehensive review paper dedicated to martensitic steels [3], the following concepts were summarized: cold treatment (>−80 • C); shallow CrT (from −80 • C to −160 • C); and deep CrT (<−160 • C); however, some authors using different cooling methods during machining have used the term cryogenic to denote any measured temperature from 0 • C to −100 • C [23][24][25][26]. It should be noted that the CrT is sometimes termed cryogenic processing, deep cryogenic processing, deep CrT, cryogenic tempering, and deep cryogenic tempering [4].…”