Influence of chemical composition and austenitizing temperature on hardenability of pm steels

The hardenability of powder metallurgy (PM) steels is an important measure of how well alloy systems can be used for sinter hardening. Several options are now available for sinter-hardening applications as new alloys have been developed over the last few years. Alloy composition has been optimized to take advantage of rapid cooling in sinterhardening furnaces while addressing the cost of the alloying elements. One of the most widely used methods for determining hardenability is the Jominy end-quench test in which bar samples are heated into the austenite range and water quenched on one end of the bar, producing a wide range in cooling rate within one sample. The hardenability of different alloy systems was examined utilizing the Jominy test coupled with sintering studies. Austenitizing temperature has an important effect on the measured hardenability of high-molybdenum-containing steels and selection of this process variable for these alloy grades has a profound effect on the predicted hardenability of different alloy systems. Thus, it is recommended that hardenability data in MPIF Standard 35 be re-evaluated at suitable austenitizing temperatures for alloys containing high levels of molybdenum and carbon.