Tribological behavior of MgO doped alumina ceramics

Abstract

In this study, the coefficient of frictions under variable normal load and reciprocating frequencies of alumina ceramics have been investigated with various level (upto 4 wt%) of nano-crystalline MgO addition. A linear reciprocating tribotester was used to carry out the experimental investigations in dry condition using a silicon nitride (Si3N4) ball as a counter surface on the sintered samples. The friction tests were performed for a sliding time of 30 min with reciprocating frequency of 15, 30, 45, 60 Hz keeping the normal load fixed at 0.5 kgf and at normal loads of 0.3, 0.5, 0.7, 1.0 kgf keeping the sliding frequency fixed at 30 Hz. The friction coefficient increases with increasing sliding frequency, normal load but decreases with nano-magnesia addition. The friction coefficient data is used to develop an algorithm following the best fit topology to predict the addition level of magnesia in alumina for given friction coefficient and sliding frequency or normal load. Among various curve fitting techniques like polynomial fit of degree two, exponential fit of degree one and two, smoothing spline and Weibull fit, with minimum root mean square error, cubicspline fit method is adopted to form smooth curves in MATLAB. The validated result lies within a maximum error of 3.37% for cubicspline fit.