Study on hydrogen behaviors around micropores within heavy forging during heating process

• Published in: International journal of advanced manufacturing technology Vol. 113; no. 1-2; pp. 523 - 533
• Main Authors: Fan, Junkai, Peng, Bo, Zhao, Wu
• Format: Journal Article
• Language: English
• Published: London Springer London 01.03.2021; Springer Nature B.V
• Subjects: CAE) and Design; Chemical potential; Computer-Aided Engineering (CAD; Cracks; Decomposition; Diffusion coefficient; Engineering; Finite element method; Forging; Forgings; Heat; Heat treatment; Heating rate; Hydrogen; Industrial and Production Engineering; Mechanical Engineering; Media Management; Original Article; Pressure effects; Hydrogen diffusion; Heating process; Micropore hydrogen pressure; Heavy forging; Hydrogen-induced cracks
• ISSN: 0268-3768; 1433-3015
• DOI: 10.1007/s00170-021-06660-z

Hydrogen and micropores are widely distributed and inevitable in heavy forgings. The accumulation of hydrogen in micropores results in the formation of higher hydrogen pressure inside. In this article, the influence of heating process on hydrogen behavior around micropores is studied by finite element method. The analysis model is established theoretically and the relationship among micropore hydrogen pressure, temperature, and lattice hydrogen concentration is derived based on chemical potential balance. The results show that, during the heating process, when decomposition condition is met, hydrogen molecules begin to decompose and diffuse out of micropores. Micropore hydrogen pressure is the result of volume expansion and decomposition of micropore hydrogen molecules. Microstructures with a smaller hydrogen diffusion coefficient are more likely to form higher hydrogen pressure in micropores during heating and are more likely to form hydrogen-induced cracks. The holding temperature has little effect on micropore hydrogen pressure. Among all heat treatment parameters, the heating rate has the most significant influence on hydrogen behavior around micropores. A larger heating rate can reduce hydrogen discharge time, but increase the micropore hydrogen pressure. From the perspective of reducing micropore hydrogen pressure and heat treatment time, a heating rate of 0.05 K/s is more appropriate. This study puts forward a new mechanism of hydrogen-induced cracking in heavy forgings and provides a new perspective for formulating heat treatment processes.