Htri Crack Repack -

HTHA, HTRI crack, hydrogen attack, decarburization, methane fissuring, Nelson curve, ultrasonic backscatter, Cr-Mo steel. 1. Introduction 1.1 Historical Context and Terminology High-Temperature Hydrogen Attack (HTHA) was first identified in the 1940s and 1950s in refinery hydroprocessing units. The term “HTRI crack” emerged from early collaborative research at the Heat Transfer Research Institute (HTRI) in California, where investigators documented intergranular cracking in carbon steel heat exchangers exposed to hydrogen at 400–500°C. However, “HTRI crack” is a misnomer; the correct metallurgical phenomenon is HTHA, and the term is now discouraged except in historical reference.

For alloy carbides (e.g., Cr₂₃C₆, Mo₂C): htri crack

[ \text{Fe}_3\text{C} + 4\text{H} \rightarrow 3\text{Fe} + \text{CH}_4(g) ] The term “HTRI crack” emerged from early collaborative

Author: [Generated for Academic Review] Date: April 2026 Abstract High-Temperature Hydrogen Attack (HTHA) is a damaging degradation mechanism affecting carbon and low-alloy steels exposed to hydrogen at elevated temperatures and pressures. Historically mislabeled as “HTRI crack” due to early studies at the Heat Transfer Research Institute, HTHA involves the internal decarburization of steel and the formation of methane bubbles at grain boundaries, leading to fissuring and loss of mechanical properties. This paper provides a comprehensive analysis of HTHA, including thermodynamic and kinetic foundations, metallurgical transformation, nondestructive examination (NDE) challenges, and modern mitigation strategies. The transition from carbon steel to Cr-Mo steels with post-weld heat treatment (PWHT) is evaluated. Recent advances in advanced ultrasonic backscatter techniques and risk-based inspection (RBI) are discussed. The paper concludes with case studies and future directions for hydrogen service in the context of a hydrogen economy. Historically mislabeled as “HTRI crack” due to early