Fatigue behavior of a low alloy P/M steel

摘要

In recent years, PM steel parts have been used due to materials saving and cost. Mechanical properties of PM parts made of Ultrapac-LA (Fe-.5Mo- 1.5Cu-1.75Ni) with 0.2 and 0.5% graphite addition have been studied. The chemical composition of Ultrapac-LA is similar to Distaloy AB. Specimens with dimensions of 89×6×5.5 mm were prepared. The green compacts were sintered at 1120°C in a 75 H{sub}2 - 25 N{sub}2 atmosphere for 40 minutes to densities in the range of 6.7g/cm{sup}3 to 7g/cm{sup}3. They were tested in static and cyclic loading, and their microstructures were studied by optical microscopy. Results show that porosity has a definite effect on fatigue resistance of this alloy. The formation of bainite and martensite at higher carbon content and proper heated treatment increased tensile strength, fatigue strength and apparent hardness, while a higher green density maintained satisfactory ductility. It was possible to achieve ultimate tensile, yield and fatigue strength as high as 882, 710 and 188 MPa, respectively, with apparent hardness of 286 HV.