Sinteraustempering Of Two Mo-(Cu)-(Cr)-(Ni)-(Mn)-C Steels In A Semi-Closed Container In Flowing Nitrogen

Abstract

Three types of heat treatment, sinteraustempering in 500°C, 400°C and 350°C; sinterhardening and sintering with cooling at the rate 10K/min) as the final operation, on steels sintered semi-closed container were investigated. Results of mechanical properties, microstructure investigations and fracture and EDX analyses are reported. The study involved two PM steels: DH-1 (Fe-2%Cu-1.5%Mo-0.5%C) and 34HNM (Fe-0.2%Mo-0.8%Mn-1.5%Cr-1.5Ni-0.4%C). Prealloyed Höganäs DH (Direct Hardening) iron powder and graphite powder (grade C-UF) were used to produce DH-1 steel. Prealloyed Astaloy CrL iron powder, low carbon ferromanganese, elemental nickel and graphite grade C-UF powder were the starting powders of 34HNM steel. Pressing was in rigid dies at 660MPa according to PN-EN ISO 2740 standard. After compaction, green compacts were sintered in a specially designed semi-closed container at 1120°C for 60 minutes in a nitrogen atmosphere. The chemical composition of the sintering atmosphere was modified by adding ferromanganese and/or activator into the container.

Keywords

• semi-closed container
• sinteraustempering
• sintering
• nitrogen
• microstructure
• mechanical properties