In order to investigate the importance of pore size and hardness on the fatigue strength of a prealloyed powder metal (Fe-3.0 Cr-0.5 Mo-0.5C mass%) with the density of ρ= 7 .Og/cm3, ultrasonic fatigue tests were conducted at a test frequency of 20 kHz in air at room temperature. The fatigue limit of the powder metal was the maximum critical stress under which fatigue cracks initiating from the pore stop propagating. Therefore, the fatigue limit was accurately predicted by the -√area parameter model, σw.= 1.43(HV + 120)/(√area)"6, for the surface defect. Here, as √[area was employed the effective maximum pore size, -√areae//, max, in the control volume of the ultrasonic fatigue specimen which was estimated from the statistics of extremes distribution of the pore sizes at the polished surface. As HV was employed Vickers hardness, HV98..1 N, of the microstructure which included both the matrix and pores. The usage of -√Jareaeff, max and HV98..1 N, in the √/area parameter model is practical use and useful for predicting the fatigue limit of the powder metal. In addition, the usage of √■<jQ.YQQ.eff, max indicates that the dominating cause of fatigue strength for the powder metal is the maximum pore size rather than the porosity or density.
|Number of pages||10|
|Journal||Nihon Kikai Gakkai Ronbunshu, A Hen/Transactions of the Japan Society of Mechanical Engineers, Part A|
|Publication status||Published - Feb 2009|
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering