EFFECT OF SINTERING ATMOSPHERE ON MICROSTRUCTURE, PROPERTIES AND FRACTURE OF Cr-Mn SINTERED STEELS

The effect of sintering at 1120°C and 1250°C in 5%H 2 +95%N 2 and pure N 2 atmosphere on microstructure, mechanical properties and fracture mechanisms of the Fe-(Cr)-(Mn)-(Mo)-C sintered steels was studied. Also sintering in air, as well using an idea of a „self-cleaning” effect of manganese was investigated. The results of investigations of mechanical properties show that the investigated alloys belong to medium strength steels with tensile and yield strengths of up to 957 and 562 MPa, respectively. The advantage of investigated steels is they have a higher hardness, up to 473 HV30. Following microstructural research, the change of fracture mechanisms from predominantly interparticle ductile mode with shallow dimples to mixture of cleavage/intergranular modes was identified for low carbon (~0.15%C) and high carbon (~0.7%C) for both levels of Cr content. The effect of the “self-cleaning” of air atmosphere with optimal addition of ferromanganese lumps reflected in strength properties comparable with N 2 and H 2 +N 2 atmosphere has been identified as a relatively positive.