Fractography on Fatigue Fracture Surface of Sintered Ferrous Materials

Abstract

The relationship between the behavior of fatigue crack growth and the pattern of fractured surface was investigated on the sintered irons and alloyed steels for various stress ratios by using 1/2 compact type specimens. The results obtained were summarized as follows:
(1) The fracture pattern in the fatigue crack growth on the sintered ferrous materials consisted of shear and intergranular fractures, striation like pattern, and pore surface.
(2) The fracture surface reflected the shear and local intergranular fractures in the region of low crack growth rate, while most of the fracture surface were occupied by the straiation like pattern in the region of high crack growth rate.
(3) As the stress ratio increased, the fracture surface in the fatigue crack growth became coarser and many microcracks appeared within the facets. This behavior was independent on the density and the addtional alloying elements.