In the first, the effects of tribologically- penetrated hydrogen on the abrasive wear properties of mild steel have been studied. The wear experiments were conducted at 25℃ in 1 N $H_2SO_4$ aqueous solution including hydrogen recombination poison such as $As_2O_3$ or in absence of it using a pin-on-disc wear machine. The amount of penetrated hydrogen into mild steel during the wear process was varied with the current density and hydrogen recombination poison. As the current density, i.e., the amount of penetrated hydrogen, increased, the wear rate decreased and then increased rapidly above critical hydrogen concentration. The abrasive wear mechanism changes from ploughing, to cutting and then to cracking with the increase in the penetrated hydrogen of mild steel. It is suggested that the penetrated hydrogen below critical hydrogen concentration decreases the wear rate, accompanied by the increase in the surface hardness due to the impedement of dislocation movement. As the hydrogen concentration exceeds the critical value, the mechanism of the wear process changes predominantly from ploughing-cutting to cutting-cracking due to the formation of voids. Cracking is promoted by increasing brittleness due to the excessively penetrated hydrogen which favours crack formation and crack propagation processes.
In the second, the kinetics of tribologically-enhanced hydrogen evolution from the mild steel have been studied by using an electrochemical extraction technique and a mass spectrometric method. The hydrogen extraction measurements allowed to quantitatively distinguish the contribution of removal of highly hydrogen-segregated layers as wear debris from that of frictional heat to the tribologically-enhanced hydrogen evolution using a simplified mathematical model. It is suggested that the hydrogen evolutions enhanced by adhesive and abrasive wear process are due to mainly to removal of highly hydrogen - segregated layers facilitated by frictional heat, respectively. After the removal of highly hydrogen-segregated layers of approximately 12-μm thickness, i.e., initial period, the equilibrium between the amount of the diffusible hydrogen and trapped hydrogen is achieved in the following stage of adhesive wear process. In that stage hydrogen is evolved as a steady state flux of hydrogen from bulk specimen. The kinetics of hydrogen evloution enhanced during the abrasive wear follow a linear time relationship after an incubation period. The steady-state hydrogen evolution rate is affected by the applied load, environmental temperature and gas atmosphere. This is discussed in terms of dislocation density at the wear subsurface, flash temperature at asperities and chemistry of oxides on the wear surface, respectively.
In the third, the effects of applied potential on the corrosive wear of Al-Si alloy have been investigated. As the applied potential increased, the wear rate remained constant in the cathodic potential region whereas the wear rate reached the maximum value at the potential of 1.08 $V_{SCE}$, and then decreased in the anodic potential region. The analysis of solution and current after the wear test allowed to quantitatively distinguish the contribution of accelerating wear loss by passivating film from that of mechanical wear loss and that of dissolution loss to the corrosive wear loss. The passivating film produced at 1.08 $V_{SCE}$ increased the corrosive wear rate whereas that produced at 3.08 $V_{SCE}$ decreased the corrosive wear rate. The abrasive wear mechanism also changes from cutting to ploughing mechanism. It is suggested that the change of the corrosive wear rate with anodic potential arises mainly from the change of the structure of passivating film from ALOOH to $Al_2O_3$.
