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An ultrasensitive hydrogen detector is described which has a detection sensitivity of a few parts per billion in the gas stream. The detector's performance, range, and accuracy were evaluated by analyzing titanium standards from the National Bureau of Standards containing known amounts of hydrogen at the following levels: 32 ± 2 ppm, 98 ± 5 ppm, 215 ± 6 ppm. The fractional random error in the mean value of these standards at 95 percent confidence level was found to be ±5.01 percent, ±1.67 percent, and ±1.08 percent, respectively. Preliminary results of the hydrogen analysis of cadmium plated steel specimens heat treated to 260 to 280 ksi strength level when compared with the notched tension testing (failure) data show that the safe limit for (total or bulk) hydrogen concentration as measured by this technique is about 1 ppm. Results on forged steel specimens heat treated to 170 to 195 ksi level indicate that here the embrittlement failure can occur at levels exceeding 2 to 2.5 ppm. Testing costs are much lower compared to notched tension tests, and the results are reliable. The objective of this paper is to expose the readers to a new hydrogen detection system and (among its other applications) its use for studying the hydrogen embrittlement problem in high-strength structural materials.
hydrogen embrittlement, notch tests, cadmium coatings, plating, heat treatment, high strength steels, titanium alloys
The Boeing Company, Seattle, Wash.