Towards Developing HIC-Resistant X70 Pipeline Grade Steel for Sour Service Applications**

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This proposal addresses the development of hydrogen-induced cracking (HIC)-resistant Ca-treated X70 pipeline grade steel for sour service oil/gas applications. The industry's need for improved HIC-resistance, in addition to higher strength and toughness as key performance properties in pipeline grade steels, is driven by the continued demand for the transportation of oil/gas products by steel pipelines coupled with the ongoing change in the oil/gas reserves (supply) from "sweet" to "sour" (H2S-containing). HIC is a brittle material fracture mode that occurs at stresses below the yield (permanent deformation) stress and involves the ingress of atomic hydrogen (H) and associated trapping at internal sites as necessary events. Internal trap sites span many length scales, ranging from constituent phase boundaries (observable using light optical microscopy) down to nanometer-sized strengthening intermetallic particles (observable using transmission electron microscopy). Individual H trap sites will first be spatially isolated and then linked to local HIC susceptibility via micro-mechanical testing (nano-indentation measurements) of micro-cantilever beams, with and without a H charging pre-treatment applied. The value of the research from a practical perspective is a science-based construction of a relative scale ranking the HIC susceptibility of individual internal trap sites. Such a ranking is vital to identify the more critical internal trap sites for the subsequent engineering of process modifications designed to control the deleterious effect of such traps. The results of this research will have medium to long term impact on: (i) sour service pipeline grade steel product development for Canadian steelmakers and (ii) operating reliability, integrity and safety of new and/or refurbished Canadian oil/gas transmission pipeline systems.**********