FAILURE ANALYSIS APPROACH TO FRACTURE STUDIES IN POWDER METALLURGY PARTS

摘要

This paper presents a failure analysis of tool steel and brass powder metallurgy (P/M) parts that failed during service. A detailed failure investigation of fractured tool steel and brass parts was carried out to assess the causes for their premature failures. The fractured surfaces of the broken pieces and the component surfaces were subjected to detailed examination. Investigations were carried out by visual methods, microhardness measurements, and using optical and scanning electron microscopes. In the case of the brass sample, visual examination of the surface indicated flat surface features. Detailed optical and electron microscopic studies corroborated by microhardness indentations have conclusively established that the failure was mainly due to the presence of very small impurities in the brass component material. In the case of the tool steel sample, the fractured surfaces of the component were subjected to destructive and nondestructive tests. Representative fractured pieces were examined visually and tested for their yield strength using simple tensile tests. Optical and scanning electron microscopies at appropriate magnifications were also performed to characterize its microstructure and fracture morphology. Detailed investigations of the fool steel part established that the failure was mainly due to inferior yield strength of the component resulting from improper heat treatment.