Heat Treatment Effect on Hydrogen Permeation and Trapping in the API 5CT P110 Steel

Abstract

The effect of heat treatment on hydrogen diffusion and trapping on the API 5CT P110 steel was investigated trough electrochemical permeation tests and microstructural analysis techniques. Samples of as-received steel were tempered at different temperatures to obtain hydrogen permeation and trapping parameters and to characterize microstructural modifications that may alter these parameters. After permeation tests on each heat-treatment condition were verified changes on hydrogen kinetic parameters. Microstructural analysis revelated changes in dislocations density and volumetric fraction of titanium carbides, responsible to alterations in diffusivity, solubility and in hydrogen trapping characteristics. As these carbides are considered irreversible hydrogen traps, are beneficial because they become the steels less susceptible to hydrogen embrittlement. Therefore, the results suggest that there is an optimal tempering temperature which can make the API 5CT P110 steel more resistant against hydrogen embrittlement, since promote the formation of a higher number of irreversible hydrogen traps.