Hydrogen-Stress Cracking of Type 410 Stainless Steel Splice Case Bolts
Type 410 stainless steel bolts were used to hold together galvanized gray cast iron splice case halves. Before installation, the bolts were treated with molybdenum disulfide (MoS2) antiseize compound. Several failures of splice case bolts were discovered in flooded manholes after they were in service for three to four months. Laboratory experiments were conducted to determine if the failure mode was hydrogen-stress cracking, if sulfides accelerate the failure, if heat treatment can improve the resistance against this failure mode, and if the type 305 austenitic stainless steel would serve as a replacement material. Based on test results, the solution to the hydrogen-stress cracking problem consisted of changing the bolt from type 410 to 305 stainless steel, eliminating use of MoS2, and limiting the torque to 60 N·m (540 in.·lb).