21.6.2005 Pressing & Sintering

PM Steel for High Loaded Applications

Diesel engine components conventionally made of wrought steel are identified as candidates to be replaced by high performance PM steel. An investigation is made on notch sensitivity and bending fatigue performance of as sintered Chromium/Molybdenum pre-alloyed Astaloy CrL and sintered-hardened Astaloy CrM. Best bending fatigue performance, 437 MPa at load ratio R=-1, is found for 1120 °C (2050 °F) sintered-hardened Astaloy CrM+0.4% graphite with addition of methane to the sintering atmosphere. Astaloy CrL+0.85% graphite sintered at 1250 °C (2280 °F) with regular cooling 0.8%C/sec have a fatigue limit of 296 MPa. Lowest notch sensitivity index in this investigation is found for Astaloy CrM+0.4% graphite followed by Astaloy CrL+0.85% graphite sintered at 1120 °C (2050 °F) and 1250°C(2280 °F) respectively.