Improved efficiency by vacuum sintering and low pressure carburizing of PM components

Heat treatment process of Powder Metal materials like Astaloy, requires four steps (De-waxing – HT Sintering – Carburizing – Surface Hardening), usually achieved in dedicated atmospheric furnaces for sintering and heat treat respectively, leading to intermediate handling operations and repeated heating and cooling cycles. Chromium alloys in particular are difficult to heat treat because chromium oxides easily form, which has a negative impact on mechanical properties. This paper presents the concept of the multipurpose batch vacuum furnace, able to realize all these steps in one unique cycle. The multiple benefits brought by this technology are summarized regarding the quality aspect and cost saving, like vacuum integrity along the entire cycle avoiding oxidation, no limitation on sintering temperature, repeatability of the process, gas quench flexibility, energy saving (no re-heating), cost savings and environmental benefits. The main goal is to use this technology to manufacture high load transmission gears in PM materials.