20th International Forgemasters Meeting - IFM 2017

It is generally accepted that hydrogen is only a contributor to failure when in its monatomic form. As a result, an important measurement in determining whether hydrogen damage is present in a material is a measure of diffusible (mobile) hydrogen. This measurement cannot currently be conducted either quickly enough or reliably enough to be used during industrial steel manufacturing. Moreover, unlike most precursors to mechanical failure, hydrogen embrittlement cannot be detected by any type of industrial nondestructive evaluation. As a result, hydrogen damage must be precluded from engineering components. To reduce the manufacturing cost and facility throughput demands associated with currently specified hydrogen soaking treatments, hydrogen mobility in high strength HY-80 steel was studied. Two heats of HY-80 were manufactured; one heat using aged lime in an induction furnace after secondary refining to create material with high diffused hydrogen, and a second heat containing high embrittling element concentrations to bound the worst case condition for the onset of temper embrittlement. The first two strategies for reducing the cost and time of hydrogen removal treatments evaluated alternate diffusion based treatments both below and within the temper embrittlement range respectively, with post austenization and tempering to recover properties for those treatments in the embrittlement zone. The second two strategies evaluated hydrogen transport by non-equilibrium processes. Both induction and vibratory treatments were used to create a controlled directional stress wave through test materials. This was done to investigate the theory of hydrogen entrapment at dislocation cores and that these dislocations would still be mobile and therefore capable of accomplishing hydrogen transport. Results for non-equilibrium strategies were inconclusive showing marginal improvements for vibratory treatments conducted on cast blocks. However, assays conducted using traditional thermal diffusion mechanisms showed the ability to reduce required soaking times by more than 30% via optimization of treatments below the temper embrittlement range, and by up to 90% via soaking in the embrittlement range at 900°F followed by a subcritical anneal and re-heat treatment.