A Review on Steels for Cryogenic Applications

Cryogenic systems have played a crucial role in almost all of the finest technological achievements of mankind. Cryogenic applications demand materials with a unique combination of properties, which drastically limits the choice of materials. In most other engineering applications, because of wide tailorability of their properties and excellent combination of strength and toughness, coupled with lower cost compared with nonferrous materials, steels have become the preferred/dominant structural material for cryogenic applications. The contradictory requirement of higher strength without compromising toughness at cryogenic temperatures posed considerable challenges and led to the development of large array of steels tailored for specific applications. This review is an attempt to survey the metallurgical aspects, material selection, mechanical property evaluation, and application of various standard and nonstandard steels for cryogenic applications. This review covers the influence of low temperatures on material properties, simulative mechanical tests for property evaluation, metallurgy of steels, and application examples surveying the published literature to date. The review also analyzes the origins of low-temperature toughness, various application requirements, and the work carried out at authors' laboratories. The issues pertaining to mechanical tests at low temperatures and status of data generation in international scenario have been critically analyzed. Physical metallurgy aspects have been highlighted in the review, and microstructure-property-processing correlations for various steels have also been covered. One of the recent advances in steels for cryogenic applications, high-entropy alloys, which are proposed as alternatives for the conventional steels, have been reviewed, and mechanical property data have been critically analyzed. The potential of additive manufactured steels for low-temperature applications has been reviewed. Finally, this review article discusses challenges in processing-mechanical properties correlation for various grades of steels for cryogenic applications. It also provides useful information for researchers working on steels for cryogenic applications with a glimpse of recent advances made in this area.