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Abstract
The strength of extruded and heat-treated bar of 18Ni 350 maraging steel produced from prealloyed powder has been found to be comparable to that of conventional, wrought 18Ni 350 maraging steel. Impact toughness was considerably higher. In contrast, properties of bar Obtained from an elemental powder mix were markedly inferior to wrought 18Ni 350 maraging steel. The high toughness of Charpy V-notch specimens produced from prealloyed powder was partly attributed to the presence of continuous, aluminium-rich stringers.This resulted in delamination of the specimens during testing and led to a fibrous fracture. Charpy V-notch specimens produced from the elemental powders also contained stringers. However, these were not continuous and therefore did not cause delamination. The resulting fracture surface was flat and relatively featureless. Electron-microprobe analysis has shown that the morphology of the stringers is largely determined by their composition and the composition at the stringer/matrix interface.
Notes
* Manuscript received 30 March 1972.