Development of a Test Method for Environmental Shear Testing of Dissimilar Metal Interfaces

Abstract Low alloy steels are often clad with nickel alloys to improve corrosion resistance, thereby ensuring the safe transport of corrosive substances that could otherwise damage the steel. Clad components are commonly used in subsea production systems for the safe transport of sour fluids and are subjected to various loading conditions; however, there are currently no standardised methods for environmental testing of dissimilar joints under shear loading. This paper details the development of a small-scale sour shear loading test method, applied to an ASTM A182 F22 (2.25Cr-1Mo) to Alloy 725 (UNS N07725) dissimilar joint. Through finite element analysis, notched specimens were designed to achieve specific levels of shear strain across the dissimilar interface. These specimens were then subjected to a constant load for at least 720 hours in NACE Test Solution B, to assess resistance to shear strain and environmentally assisted cracking. Additional specimens underwent testing to failure under slow rising displacement after the load hold period, to determine the failure load and fracture mechanisms. This method shows promise as a screening test for evaluating the integrity of dissimilar interfaces against environmental cracking under shear loading conditions.