In my previous post I noted that the nanostructured coating showed enhancements in wear-resistance (2 to 4X); bond strength (up to 2X); and toughness, compared to its conventional coating counterpart. In the most severe wear applications, toughness, or survivability, is the most important characteristic of a coating. The enhanced toughness stood out as a unique feature of this coating, especially considering that the coating materials were ceramics. The source for the enhanced toughness found in the nanostructured ceramic coating was revealed by examining the crack patterns formed by micro-indentations.  It was apparent that the commercial coating had a higher number of wider and longer cracks as compared to the nanostructured coating.  Closer examination of the region around the cracks in the nanostructured coating revealed an interesting connection between the presence of nano-porous, unmelted or partially-melted particles and crack propagation.  These fine-pored agglomerates seemed to deflect the crack and/or blunt the crack tip, thus hindering its propagation.  The same effect was not observed on dense unmelted particles found in the commercial coating.  The enhanced toughness in the nanostructured coatings was likely the key feature that contributed to their far superior wear-resistance.

George E. Kim, Ph.D.

F.W. Gartner

Perpetual Technologies, Inc.

email: gkim@perpetualtech.ca