Hydrogen solubility in pure iron and effects of alloying elements on the solubility in the temperature range 20 to 500° C

Abstract

Hydrogen solubility in pure iron and iron based binary alloys have been measured in the temperature range 20 to 500° C under hydrogen at atmospheric pressure. For pure iron, hydrogen solubility decreases as the temperature decreases until about 300° C and then increases reaching maximum at 80° C. The maximum solubility at this temperature was about 0.9 ppm. This large value is thought to result from chemisorption of hydrogen at the grain boundary. The addition of alloying elements, Mo, W and Ni increased the temperature at which hydrogen solubility had its maximum and had no other effects on the trend of hydrogen solubility change as a function of temperature for pure iron. The higher heats of chemisorption of hydrogen onto Mo and W compared with Fe may be responsible for the change in temperatures. Other possible methods of trapping hydrogen in iron and iron based binary alloys are discussed.