Tribological behavior of alumina obtained by low-pressure injection molding using factorial design

摘要

This work presents a tribological study of ceramics parts produced by low-pressure injection molding (LPIM) using factorial design technique. An experimental design of 2k + no was used to define the experiments and evaluate the influence of three variables on friction coefficient, wear rate and wear mechanisms. The normal load (5 N to 15 N), tangential velocity (0.05 m s(-1) to 0.15 m s(-1)) and counterbody type (with three contact pairs, alumina-alumina, alumina-silicon nitride and alumina-steel) were selected as the input variables. Discs of ceramic with phi 20x3 mm composed by 86 wt% alumina (99.8 % Al2O3) and 14 wt% organic vehicle were produced by LPIM process and sintered at 1600 degrees C, and used as samples in tribological tests. Unidirectional sliding wear tests were conducted in unlubricated conditions at room temperature using a ball-on-disk tribometer. The statistical analysis indicated that the friction coefficient and the specific wear coefficient were strongly sensitive to the individually variations of velocity and the counterface type, and especially to the interaction between these factors. The wear behavior was analyzed as a function of contact parameter that considered the contact Hertz pressure, velocity and hardness of the materials in contact. The hardness and the chemical nature of the counterface were determinant in the reduction of friction coefficient and the severity of LPIM-alumina wear. It was identified also that the transfering of oxide films from the active counterfaces protected the LPIM-alumina from severe wear and reduced the coefficient of friction, wear rate and brittle fracture of the structural ceramic.