Effect of normal load on two-body abrasive wear of an Fe-B-Cr-C based alloy with minor Cu and Ni additions

Abstract

During the abrasive wear process of Fe-B alloy, the Fe2B resists the abrasive and protects the matrix from being shoveled off; in return, the matrix supports the Fe2B against fracture. Therefore, there is a need to characterize the effect of matrix on the abrasion resistance of Fe-B alloy. Two-body abrasive wear tests of as-cast Fe-B alloys with various matrix contents are performed on a pin-on disk tribometer at the normal load ranging from 7 N to 30 N. At the load of 7 N, the abrasion resistance of Fe-B alloy increases with increased Cu and Ni contents, especially for the high Cu and Ni additions (namely, the Vm/Vp becomes greater than 3.7 (where the Vp and Vm show the volume fractions of pearlite and martensite, respectively)), and the wear mechanism changes from micro-ploughing to micro-cutting. Nevertheless, the abrasion resistance of Fe-B alloy decreases with the increase of normal load. At the same time, the wear mechanism changes from micro-cutting to a mixed mode of micro-cutting and micro-ploughing. The wear mechanism of Fe-B alloy can be described as follows: with the decrease of Vm/Vp or the increase of normal load, the M2B-type boride will be crushed by a perpendicular force F⊥ owing to a high degree of deformation, and the broken M2B debris will be eradicated and dislodged by the Al2O3 abrasives, then the abrasion resistance of Fe-B alloy will be reduced greatly. Accordingly, it has been proven that the Fe-B alloy with martensite matrix or high Vm/Vp matrix can be effectively subjected to severe abrasive wear in a low contact stress.