Comparison of Carburizing and Boronizing Processes on Mechanical and Wear Properties of PM Parts

In this study carburizing and boronizing processes were applied to powder metallurgy steel specimens and the mechanical and tribological properties of the substrate and coatings were evaluated under various process conditions. The specimens, made from industrial test pieces, were carburized in a powder pack for a duration of 2-5 hrs at 850-950 ˚C. Similar specimens were pack boronized for 4 hrs at 950 ˚C. The effect of austenitization-quench treatment was also investigated on some specimens. The wear tests were carried out by means of a pin-on-disc tribotester against ball bearing steel. The results indicate that by appropriate selection of process parameters it is possible to obtain high wear resistance together with moderate toughness. Boride layers with hardness values of 1700HV are properly formed on PM samples. The wear resistance, therefore, is significantly increased with practically no reduction in impact resistance. It is concluded that boronizing treatment can be more suitable for some PM parts under tribological conditions.