Wear-resistant boride composites with high percentage of reinforcement phase
A highly wear resistant sintered, hot pressed, or otherwise compacted ceramic composite material is described, consisting of two discrete phases of the form AlxMgyB14 where x and y ≦1 or like hard, orthorhombic compounds, and TiB2 or like Group IVB transition metal di-borides, and with an unexpectedly high contentof transition metal di-boride in the range from 40 to 90 percent (28 to 85 volume percent).
The measurement of wear resistance
Abstract This is a discussion of several important aspects of evaluating wear resistance. It is focused on abrasion, which is a large area of the complex field of wear. There is no universal wear test . Instead it is necessary to analyze the factors that are most important in a given wear situation and to evaluate these separately or in simple combinations. Such evaluations or tests have the aim of making possible the wise selection of materials and the prediction of service performance. A good wear test should have demonstrated reliability (which is the same as reproducibility), ranking ability, and validity. The merit of these several qualities should be checked by statistical mathematics to avoid erroneous conclusions and misplaced confidence. Simplified statistical tests are provided here to facilitate such checking. This discussion is illustrated with data from a laboratory abrasion test that has a useful relation to ball mill wear. It is only one of several that apply to important areas of abrasive wear, but it illustrates a desirable approach to the problem of material selection.
Wear mechanism of plasma-sprayed alumina coating in sliding contacts with harder asperities
The wear mechanism of plasma-sprayed alumina was studied by scratching a model alumina coating using a diamond indenter. Single scratching on polished virgin surface, repeated scratching over the same track and parallel interacting scratching were investigated. The predominant mechanism of material removal was found to be microfracture within the quasi-plastic zone, which takes place preferentially at splat boundaries and pre-existing cracks and is driven by inelastic strain. When scratching was made on a virgin surface the wear rate was relatively low, but when parallel scratches interacted, subsequent scratching was made on already heavily strained material, thus, the wear rate was much higher. The wear debris produced during single and parallel interacting scratching was in the form of small angular particles whose dimensions were related to the splat structure and pre-existing cracks. In repeated scratching over the same track, surface material experienced repeated inelastic deformation and, thus, crack development at the splat boundaries, and this resulted in the production of thin platelet wear debris.