Fracture Toughness and Fatigue Resistance of a Range of Sintered Steels

Abstract

A range of notched, sintered maraging and diluted maraging steel compacts have been fatigue tested in three point bending with two levels of notch root radii. The number of cycles to produce a detectable fatigue crack correlated well with an empirical parameter of the form ( ΔK/ p^0.3), thereby minimising the banding effect, possibly characteristic in these sintered steels. Decreased fatigue resistance have been observed with increased sintered density above a eritical porosity level. Comparatively higher crack growth rate have been found in the highly diluted maraging steel compacts due to the presence of soft ferrite in the matrix, which largely superseded the crack blunting effect due to porosities. The micromechanism of fracture was of ductile dimple type in every case.

In the sintered materials tested so far, including some sintered specimens of the Ancoloy SA (Hoganas)  variety, the increase in toughness value with the increased yield stress seemed to be the basic trend - a trend which would carry them into competition with the high-strength wrought steels.

Date of Award	Dec 1976
Original language	English
Awarding Institution	Aston University