Cryogenic Treatment of Martensitic Steels: Microstructural Fundamentals and Implications for Mechanical Properties and Wear and Corrosion Performance

Abstract

Conventional heat treatment is not capable of converting a sufficient amount of retained austenite into martensite in high-carbon or high-carbon and high-alloyed iron alloys. Cryogenic treatment induces the following alterations in the microstructures: (i) a considerable reduction in the retained austenite amount, (ii) formation of refined martensite coupled with an increased number of lattice defects, such as dislocations and twins, (iii) changes in the precipitation kinetics of nano-sized transient carbides during tempering, and (iv) an increase in the number of small globular carbides. These microstructural alterations are reflected in mechanical property improvements and better dimensional stability. A common consequence of cryogenic treatment is a significant increase in the wear resistance of steels. The current review deals with all of the mentioned microstructural changes as well as the variations in strength, toughness, wear performance, and corrosion resistance for a variety of iron alloys, such as carburising steels, hot work tool steels, bearing and eutectoid steels, and high-carbon and high-alloyed ledeburitic cold work tool steels.

Effect of Cryogenic Treatments on Hardness, Fracture Toughness, and Wear Properties of Vanadis 6 Tool Steel

“…However, the 4%C-19%Cr-4%W alloy outperformed all the other alloys, with much lower carbide amounts despite comparable bulk hardness. Many examples of the beneficial effects of carbide phases have been reported in one of the most recent review papers [36]. At this place, it should be noted that, in 1994, Meng et al [37] observed that cryogenic treatments foster the precipitation of transient η-carbides at low tempering temperatures.…”

Effects of Cryogenic- and Cool-Assisted Burnishing on the Surface Integrity and Operating Behavior of Metal Components: A Review and Perspectives

“…The benefits of low-temperature effects on the structural modification of metallic components have only been realized and exploited during the last 100 years and are a direct consequence of advances in science and technology that enable the creation of ultra-low-temperature environments [2]. Previous studies [3] have shown that such approaches were already attempted in the first half of the last century, whereby negative temperatures were used to improve the operational behavior of watch parts, engine blocks, military aircraft components, and chainsaw blade links. Liquefied carbon dioxide was used as a coolant in machine operations as early as 1919 [2].…”

“…Cryogenic is derived from the Greek word "κρ ύoς" meaning cold. Cryogenic conditions have a very wide range of applications in modern engineering: to improve the properties and operational behavior of steels (martensitic [3][4][5][6][7] and austenitic [8][9][10][11][12]) and non-ferrous alloys [13,14], workpieces [15], finished components [3] and tools [16][17][18], and as a cooling medium for machining [19][20][21][22] and plastic deformation [2]. It is, perhaps, for this reason of broad applicability that there is no consensus among researchers on temperature-based terminology.…”

“…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].…”

“…Therefore, using the same method but with different magnitudes of the governing factors, many deforming processes can be undertaken, and, as a result, the processed components will have different surface integrity (SI) values. During the last two decades, numerous review papers have been published, primarily dedicated to (1) autonomous CrT of steels [3,[71][72][73], tool materials [74], cutting tools [75], steels and non-ferrous alloys [76], and (2) CrA machining [2,[77][78][79][80]. However, excluding Jawahir et al [2], in which some attention is paid to burnishing, there is no comprehensive review paper dedicated to CrA burnishing.…”