Influence of Trace Water and Oxygen in a Hydrogen Environment on Pure Fe Friction and Wear

Abstract

The influence of trace water and oxygen in a hydrogen environment on the sliding behavior of pure iron was studied using a newly developed pin-on-disk apparatus in a vacuum chamber equipped with an advanced gas replacement system. The hydrogen environment in the siding tests contained 0.5 to 95 ppm water and 0.07 to 2 ppm oxygen; a turbo-molecular pump was used for evacuation and a chemical filter for reducing water and oxygen in the hydrogen gas supplied to the chamber. The concentrations of water and oxygen in the hydrogen overflow from the chamber were determined using moisture and oxygen sensors, respectively. Other potential contaminant gases were analyzed using a quadrupole mass spectrometer during evacuation and were found to be insignificant. The amount of wear and the appearance of wear debris as well as the sliding surfaces were significantly different for the different concentrations of water and oxygen. The roles of these gasses are discussed.

Influences of Trace Water in a Hydrogen Environment on the Tribological Properties of Pure Iron

“…The relationship between concentrations of water and oxygen in hydrogen environments for this study is shown in Fig.3 in comparison with that for the previous study [5]. It is confirmed that all of oxygen concentrations for this study were within 6.5 ppb regardless of a water concentration which ranged between 2 and 8,500 ppb.…”

“…After confirming that concentrations of water and oxygen in the gas were stabilized at the targeted values, a sliding test was started. Table 2 shows experimental conditions and these conditions are same as ones used in our previous studies [1,4,5,8]. To know the influences of atmospheric gases, moderate values for a load and sliding speed were selected.…”

“…Another issue which was left unsolved in the last study is separating the influences of oxygen and water from each other. The experimental technique used in our previous studies [4,5] could not control the concentrations of oxygen and water independently.…”

“…Over the past several years, the authors' research group has studied the influences of a hydrogen environment on tribological properties of various materials [1][2][3][4][5][6][7][8]. The studies were motivated by the significance of hydrogen as an energy carrier and the necessity for overcoming its congenital defect, i.e., low energy density in terms of volume.…”

“…To know the influences of oxygen and water more precisely, a pin-on-disk apparatus with an advanced gas replacement system was developed [5]. Sliding tests of self-mated pure Fe had been conducted in vearious hydrogen environments which contained trace oxygen and water ranged in 60 to 2,000 ppb and 500 to 100,000 ppb, respectively.…”