Sliding wear of Cr–Al2O3–ZrO2 and Mo–Al2O3–ZrO2 composites

The sliding wear behavior of a number of reactively sintered metal–alumina-composites (s-MAC) containing zirconia and pure alumina and yttria-stabilized zirconia (3Y-TZP) reference materials were investigated using a ball-on-disk method. Samples were tested against stainless steel (s/steel) and 3Y-TZP ball-sliders. Two series of tests were performed, firstly the samples were tested at low loads against both ball materials and in the second series, the Cr containing composites were tested against the s/steel sliders using increased loads. At low loads, tests against s/steel balls showed no significant differences between samples containing Cr when compared to samples containing Mo. Cr-bearing composites tested against 3Y-TZP showed lowest specific wear rate for this combination of couples. At the low loads no clear correlation was found between hardness and specific wear rate. One Cr containing material showed significantly lower wear than 3Y-TZP, even though it had a slightly lower hardness. Specific wear rates for 3Y-TZP slider balls were significantly higher than for s/steel balls, regardless of the disk material. At high loads, s/steel ball-metal transfer to the specimen disk becomes the dominant “wear” mechanism. This phenomenon occurred to such an extent that the specific wear determined for the sample disks was negative.