Abstract
It is stated that the technique termed Electron Microfractography may become an important tool in an analysis on metal fracture. In the present work an application of this technique was examined to reveal the details of failure phenomena of sintered WC-Co alloy. Characteristics of failures were classified in three types from the feature of fracture surfaces. They are type A of cleavage steps fractured in WC grain, type BC of flat or lined face fractured in WC-WC grain boundaries or WC-Co inte-rfaces and type D of tear drops fractured in cobalt layer. On the basis of this classification, a model diagram of the fractures associated with WC grain size and cobalt content was drawn. 1) Type A appeared in the region where WC grain size is larger than about 5μ and Co con-tents are less than about 15%, 2) Type BC appeared in the region where WC grain size is smaller than about 2μ and Co contents are less than about 7%, 3) Type D appeared in the region where WC grain size is smaller than about 4μ and Co contents are more than about 20% and 4) Mixed types of fractures appeared in the intermediate regions between above three regions. This diagram was very useful for the Electron Microfractography of sintered WC-Co alloys.
