Theses and Dissertations

Issuing Body

Mississippi State University


Rhee, Hongjoo

Committee Member

Doude, Haley R.

Committee Member

Limmer, Krista

Date of Degree


Document Type

Graduate Thesis - Open Access


Mechanical Engineering

Degree Name

Master of Science (M.S.)


James Worth Bagley College of Engineering


Department of Mechanical Engineering


High hardness steels can be affected by delayed brittle cracking often attributed to hydrogen embrittlement. Improved resistance to hydrogen embrittlement would be beneficial to many industries including military, automotive, and high-rise construction. While other prevention methods include coating, trapping, and barriers, design efforts in this study were focused on improving intrinsic properties to be more resistant to hydrogen embrittlement. Four alloys targeting 477 – 534 HB were designed and produced in-house and compared against a commercial grade 500 HB alloy. Charpy V-notch (CVN) impact toughness and tensile specimens were made according to ASTM E23 and ASTM E8 to characterize mechanical properties. Hydrogen embrittlement testing was performed using ASTM E8 test samples electro-chemically charged in either sodium hydroxide or sulfuric acid with thiourea in solution. Results suggested that alloying for lower strength and better toughness by reducing C and Mn results in lower hydrogen embrittlement susceptibility.