LUBRICANT REMOVAL IN METAL-POWDER COMPACTS

Four lubricants, zinc stearate, lithium stearate, Acrawax C, and Kenolube P11 were examined for their burn-off characteristics under different atmospheres, dew points, heating rates, and temperatures. From thermo-gravimetric analysis (TGA) and residual carbon measurements, it was shown that when water vapor was introduced in the atmosphere, the debinding rate neither increased nor decreased, contrary to previous findings in which water vapor was shown to impede debinding. However, in high dew point atmospheres, carbon soot on the surface of the part was completely removed. Results also showed that a higher hydrogen content, higher temperature, and slower heating rate enhanced binder removal. The green density had no effect on debinding over the range studied. Among the four lubricants examined, Acrawax C gave the lowest amount of residue, followed by Kenolube P11, lithium stearate, and zinc stearate. These observations support those from previous experiments performed in a N2/10%H-2 atmosphere.