The structure, hardness, carbon content and amount of stabilized austenite of a boron cast iron, subjected to various austemperings, and their effects on the resultant wear properties were investigated. The wear tests consisted of friction pairs, where the test pieces were made of B-cast irons previously austempered under various temperature and time conditions. The other friction pair component consisted of a Cr-plated alloyed cast iron. It was found that optimum wear properties were exhibited by austenitizing at 890C for two hours, followed by austempering at 350C for two hours. Under these conditions the resultant microstructure was predominantly fine bainite coupled with retained austenite (approximately 25 vol%). This structure exhibited a hardness of 42 HRC and possessed a wear resistance that was approximately nine times superior to that found in conventional B-cast irons. Moreover, the retained austenite was carbon rich, and contents of up to 2 wt% were found to go into solid solution in the γ-phase. Prolonged exposure to relatively high temperature austemperings promoted the decomposition of C-rich austenite into coarse bainite and cementite. Under these conditions, the wear properties of the B-cast iron were significantly impaired and the austempering treatments were no longer effective in improving the wear life.
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