Fiber optic sensor for diffusible hydrogen determination in high-strength steel

With the increasing use of higher strength steels, the hydrogen content necessary to promote hydrogen assisted cracking (HAC) has become very small. This much lower hydrogen content level is approaching the uncertainty level of present diffusible hydrogen analytical practices, thus requiring the development of new analytical techniques. Efforts are being made to develop more sensitive and less time consuming methods for hydrogen measurement. An advanced design for a transition metal oxide based fiber optic diffusible hydrogen sensor has therefore been developed. The sensor allows measurement of hydrogen content directly from a welded structure, eliminating the need for duplicate welded coupons. The sensor generates the necessary analytical signal in less than one hour, and has been calibrated to yield results in ml H2100 g weld metal. The sensor is also extremely sensitive to hydrogen and relatively inexpensive. The sensor shows excellent promise as an advanced hydrogen measurement technique, and research is continuing to establish procedures for transfer to industry.