BS in Materials Engineering
Materials Engineering Department
Hydrogen embrittlement of high-strength steel (4340M) was quantified through tensile testing and fractography (SEM). Three types of samples were obtained: rotating beam fatigue specimens, round (notched) tensile specimens, and flat panel specimens. In addition, three different plating types were analyzed (Ni, Cr, Cd-Ti) with a set of samples that was shot peened and a set that was not. Since some of the samples went through a hydrogen relief bake, another factor in our experiment was the amount of time it took for the samples to reach the baking process after they were electroplated (bake delay). There were three levels of bake delay that were studied for each type of plating: specified bake, delayed bake, and no bake. The notched tensile specimens and the rotating beam specimens were tensile tested, and their fracture surfaces were imaged and analyzed. The flat panel specimens were notched and manually fractured in a vise, and fractography was performed to characterize failure modes. To determine the amount of hydrogen input and release from the various samples, LECO combustion analysis was performed. The hydrogen content was used to correlate the various processing conditions (electroplating type, shot peening, bake delay) to their tensile properties and failure modes.