A comparison study of wear and fretting fatigue behavior between Cr-alloyed layer and Cr-Ti solid-solution layer

This work reported a comparison between the wear and fretting fatigue (FF) behaviors of a Cr-alloyed layer and a Cr-Ti solid-solution layer. The hardness and toughness of both layers were evaluated to support this comparison. The results showed that the Cr-alloyed layer had high surface hardness but poor toughness, while the Cr-Ti solid-solution layer had excellent toughness but low hardness. The FF properties of the modified Ti6Al4V alloy depended on the trade-off between two factors: wear resistance and fatigue resistance. Although the Cr-alloyed layer could effectively resist the wear in fretting areas, its poor toughness caused the fatigue resistance to drop sharply and hence led to a premature failure in FF test. Due to the relatively good fatigue resistance, the Cr-Ti solid-solution layer had slightly higher FF life than that of the Cr-alloyed layer; however, its low hardness resulted in severe wear in correspondence with the fretting area and thus a failure to improve the FF properties of Ti6Al4V alloy. When combined with shot peening post-treatment, the FF life of both layers increased by about three times compared to that of the Ti6Al4V alloy. A further study showed that the poor toughness or low hardness still exerted negative influence on combination-treated samples.