Nanostructured Cr-C Coatings for Application at High Temperatures

M. J. L. GINES; F. J. WILLIAMS; C. A. SCHUH

Journal of applied surface finishing

NASF

Lugar: Washington; Año: 2007 vol. 2 p. 112 - 121

1559-9590

Unlike common hexavalent Cr-based coatings, those pro- duced from trivalent baths can exhibit significant functional property enhancements upon heating, either in-situ during service, or prior to service during an annealing step. These property changes arise from evolution of the structure and phases in the deposits, and it is the purpose of this inves- tigation to discuss in more detail the processing-structure- property relationships of annealed Cr-C deposits derived from carbon-containing trivalent baths. These coatings are amorphous in the as-deposited state, but chromium nano- crystallization and carbide precipitation occur when they are subjected to thermal treatments similar to those encountered in practice. Transmission electron microscopy and x-ray dif- fraction line analysis reveal the evolution of structure on the nanoscale, while microhardness and wear resistance are dis- cussed with reference to the structural evolution.