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Gigacycle Fatigue Crack Initiation in Cr-Mo Prealloy Sintered Steel
Xu Chen,Danninger Herbert,Khatibi Golta,Weiss Brigitte 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
Crack initiation and short crack propagation was studied on the polished notched surfaces of Cr-Mo prealloy sintered steels with 7.35 sintered density. An ultrasonic resonance test system operating in push-pull mode at 20 kHz and R=-1 was used. It showed that crack initiation took place in several places, small cracks growing oriented to the local pore structure rather than to stress orientation. Their growth rate is markedly higher than the corresponding one of long cracks. Finally, several microcracks join to form a dominant crack.
Gigacycle Fatigue Endurance Strength of High Density Mo and Cr-Mo Prealloyed Sintered Steel
Xu Chen,Danninger Herbert,Khatibi Golta,Weiss Brigitte 한국분말야금학회 2006 한국분말야금학회 학술대회논문집 Vol.2006 No.1
For attaining optimum fatigue resistance of PM steels, high density levels are necessary. In this work, sintered steels Fe-1.5%Mo-0.6%C and Fe-1.5%Cr-0.2%Mo-0.6%C were produced with density levels of 7.1 to . Ultrasonic fatigue testing with 20 kHz was performed in push-pull mode up to 10E9 cycles. It was shown that the fatigue endurance strength is strongly improved by higher density levels, but also higher sintering temperatures are beneficial. The Cr-Mo steels proved to be superior to the plain Mo alloyed, due to a more favourable as-sintered matrix microstructure.