EFFECTS OF TRIBOLOGICALLY-PENETRATED HYDROGEN ON THE ABRASIVE WEAR OF MILD-STEEL IN H2SO4 SOLUTION

Abstract

The present work examines how tribologically-penetrated hydrogen affects the abrasive wear of mild steel in H2SO4 solution. The pin-on-disc type wear tests were carried out as a function of applied load at 298 K in 0.5 M H2SO4 aqueous solution in the presence and absence of 10(-4) As2O3 mol l-1 as a hydrogen recombination poison with and without concurrent hydrogen-charging into the mild-steel pin specimen. Hydrogen-charging was electrolytically made for 4 h as a function of current density of 0.5 to 100 mA cm-2. Subsequently, hydrogen-extraction measurements were performed from the worn pin specimen by using electrochemical hydrogen permeation technique, in order to determine the amount of hydrogen tribologically-penetrated into the pin specimen. The increased amount of the penetrated hydrogen by abrading action indicated tribologically-enhanced hydrogen penetration. The amount of penetrated hydrogen increased with charging current density or by addition of hydrogen recombination poison. As the current density increased, the corrosive-wear rate decreased and then increased, regardless of applied load or addition of hydrogen recombination poison. This indicated that a critical amount of the penetrated hydrogen exists, which is necessary for transition to cracking and dominates the mechanism in abrasive wear. Two-staged variation of the corrosive-wear rate with respect to the amount of penetrated hydrogen is discussed in terms of ploughing/cutting to cutting/cracking transition in the mechanism of abrasive wear.