Influence of Sintering Temperature and Cooling Rate on Microstructure and Mechanical Properties of Pre-alloyed Fe-Cr-Mo Powder Metallurgy Steel

摘要

Influence of carbon content, sintering temperature and cooling rate on microstructure and mechanical properties of a Fe-Cr-Mo alloy has been investigated. Graphite powder with varying wt% (0.4 and 0.8) was mixed with Fe-Cr-Mo prealloyed powder. The green preform compacts of 32 mm diameter were prepared by pressing in a cylindrical die at 650 MPa. The compacts were sintered for 1 h in a flowing gas mixture of 90% N-2 +10% H-2. Two different sintering temperatures (1120 and 1200 degrees C) were used. The sintered compacts were cooled at 3.5 degrees C/min or 6.0 degrees C/min. It was found that the higher sintering temperature of 1200 degrees C resulted in improved mechanical properties. Ferrite with pearlite was mostly observed in alloy with 0.4 wt% C while in 0.8 wt% C alloy, a carbide network was also observed. Graphite particles were observed at the prior particle boundaries in some of the alloys. The Fe-Cr-Mo-0.4C alloy processed at 1200 degrees C with 6.0 A degrees C/min exhibited best strength and ductility. The observed properties were correlated with the microstructure.