Criteria of Material Failure in Relation to Hydrogen Saturation

Abstract

A steadily rising interest which specialists in various fields show towards the problem of hydrogen affecting metallic materials and causing their failure is connected to all-increasing requirements set on the durability of machines and equipment in operation. Metallic structures are most often surrounded by such environment which contains hydrogenous components or hydrogen itself (in chemical industry, power engineering, etc). And it leads to various types of degradation in metals (hydrogen embrittlement, hydrogen corrosion, and so on), which, in its turn, could cause catastrophic results. Ultimate strength is considered to be a representative parameter of the process of hydrogen degradation in steels. The authors cite the results of testing conducted on hydrogen-saturated specimens made of A516-55 steel which register a significant decrease in the ultimate strength. It is proposed to use a diagram which describes a fall in metal strength and transition of structural materials into their brittle states following an increase in hydrogen concentration. Discussion is made on criteria for hydrogen-saturated materials of metallic structures failing when a momentary overload occurs under default working conditions.