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 XDTM ZL201–TiB2 in situ composite
The microstructure and dry sliding wear behaviour of XDTM ZL201–TiB2 in situ composite were studied by scanning electron microscopy, transmission electron microscopy, X-ray diffraction, pin-on-ring friction and wear testing. The microstructural constituents of the ZL201–TiB2 composite aged at 175°C for various ageing times were found to be dispersive submicrometre TiB2 particles, fine θ″, θ′-precipitates and α-Al solid solutions. As contrasted to the unreinforced ZL201 alloy, the ZL201–TiB2 composite possessed a higher microhardness and wear-resistance as well as a shorter ageing time for peak hardness. With the increase of sliding distance, transition of the dominant wear mechanism for the ZL201–TiB2 composite occurred from adhesive wear to fatigue wear in sliding contacts. At the earlier stages of wear, adhesive wear characteristics featured by mild scratchings and plastic smearing were observed on the worn surface and platelet-type wear debris; but at the later stages, contact fatigue failure of a relatively thick surface layer in relative motion, which revealed a build-up of layer-like structure and the presence of spherical particles of debris, became the dominant factor for the removal of composites. © 1998 Chapman & Hall