FAILURE ANALYSIS APPROACH TO FRACTURE STUDIES IN POWDER METALLURGY PARTS

摘要

This paper presents the failure analysis of tool steel and brass powder metallurgy (P/M) parts failed during service. A detailed failure investigation of fractured tool steel and brass parts were 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 brass sample, visual examination of the surface indicated flat surface features. Detailed optical and electron microscopic studies corroborated with microhardness indentations have conclusively established the failure was mainly due to the presence of very small impurities in brass component material. In the case of tool steel sample, the fractured surfaces of the component were subjected to destructive and non-destructive 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 microstnictiire and fracture morphology. Detailed investigations of the tool steel part established that the failure was mainly due to inferior yield strength of the component resulting from improper heat treatment.