Wear and friction studies of alumina: Correlation with electron triboemission
Mazilu, Dan A.
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The first question addressed in this thesis is whether the cumulative triboemission from the abrasion of alumina by a diamond indenter (repeat-pass sliding) correlates with the volume of material removed and, in particular, whether transitions in the rate of material removal are mirrored in the cumulative triboemission rate. As a function of load and number of diamond passes, several wear regimes are observed that are characterized from SEM micrographs by different relative proportions of plastic flow material and fractured surface in the wear scar. In all but one wear regime, the correlation between the wear volume and cumulative triboemission is modest (linear regression coefficient R2 = 0.71); including the one atypical wear regime worsens the correlation. The wear volume and cumulative triboemission are shown to be random variables with normal and lognormal distributions, respectively. Again, excluding the atypical wear regime, the correlation between the logarithms of the estimated population means is significantly better (R2 = 0.91) than the correlation between wear volume and cumulative triboemission for individual samples. In addition to the overall correlation between wear volume and cumulative triboemission, transitions from one wear regime to another are marked by changes in the slope of the mean cumulative triboemission versus pass number. These transitions correlate with the relative fraction of plastic flow debris in the wear scar. The second question addressed in this thesis is whether the introduction of the chemical vapor aluminum tri-sec butoxide, [C2H5CH(CH3)O]3Al, ATSB, into the boundary layer of an alumina-on-alumina sliding contact can reduce wear and friction. A split-plot factorial experiment was conducted; the factors tested, in addition to the presence or absence of ATSB, were normal load, sliding speed, and surface roughness. The main conclusions of the experiment are that ATSB has no statistically significant effect on specific wear, but that the presence of ATSB reduces friction by 21% at low sliding speed (0.02 m/s) and increases friction by 26% at high sliding speed (1.2 m/s).
- Doctoral Dissertations