Structure refinement effect on two and three-body abrasion resistance of high chromium cast irons

The effect of structure refinement on wear resistance of high chromium cast irons was investigated. The alloys were casted in molds containing a chill at the bottom in order to create a gradient of cooling rates, resulting in structures with carbide mean free paths ranging from 6.6±1 to 27.3±3 μm. Two-body abrasive wear tests were carried out on a pin-on-garnet paper tester model PLINT TE79 as described in ASTM G132 standard, and three-body abrasive wear tests on the Dry Sand Rubber Wheel (DSRW) abrasion tester as described in ASTM G65 standard. Wear coefficient decreased sharply from 6.6 to 15 μm of carbide mean free path and minor variations were obtained for coarser structures. All the samples showed cracking and fracture of M7C3 carbides. However, for the coarse structure it was verified that most of the larger M7C3 carbides showed only subcritical cracking and no fracture. The results suggest that the wear properties are not dependent on the bulk material hardness, but depend on structure refinement.