National Physical Laboratory

Controlled Fracture of Tool Materials

Video showing controlled crack growth in WC-6%Co hardmetal

Secondary electron
Secondary electron image (formed by Electron Back-Scattered Diffraction Analysis) from cracked WC-11%Co hardmetal

Crystal orientation
Crystal orientation image (formed by Electron Back-Scattered Diffraction Analysis) from cracked WC-11%Co hardmetal

Many tool materials that are crucial to efficient manufacturing are made from materials such as ceramics and hardmetals. These materials typically are exceptionally strong, but suffer from low toughness so that final failure occurs through catastrophic fracture processes. Developing a better understanding of these mechanisms so that optimised tool materials can be manufactured is dependent on producing quantitative ways of controlling crack growth in these materials.

With SR funding, a world leading test system has been constructed that can carry out in situ slow crack growth experiments in a high resolution SEM. The system employs closed loop force feedback using a piezoelectric actuator to enable precise control of crack kinetics. Tests have been carried out on a range of WC/Co hardmetals with different grain sizes and binder phase contents. Electron Back Scattered Diffraction (EBSD) analysis of areas around the crack tip has been correlated with microstructural observations of the crack path, and with measurements of the strain field around the crack determined through in situ image correlation.

Last Updated: 21 Feb 2012
Created: 25 Jul 2007

Registration

Please note that the information will not be divulged to third parties, or used without your permission

Login