EFFICIENCY AND TEMPERATURE RANGES OF ACTIVITY OF DIFFERENT REDUCING AGENTS DURING SINTERING OF CR-PREALLOYED PM STEELS

Paper i proceeding, 2014

Sintering of high-performance PM steel components requires development of strong inter-particle necks and the vital prerequisite for their formation is successful removal of surface oxides. In the case of water-atomized powder prealloyed with chromium, surface oxide is composed of mainly iron oxide layer with some presence of more stable fine particulate oxides. Hence, as minimum full removal of the iron surface oxide layer during sintering is required. This can be achieved by a number of gaseous reducing agents (H2, CO or mixture of both) as well as by admixed graphite. The present study is focused on the analysis of the reducing ability of the different sintering atmospheres (concentration of active gases ≤10 vol.%) and their combined effect with different graphite grades by means of thermal analysis and microscopy techniques. Results indicate that combination of the dry hydrogen-containing atmospheres and fine graphite grades allows successful sintering of chromium alloyed PM steels.