G. E. Kim, Perpetual Technologies, Inc., Ile des Soeurs, QC, Canada; M. Brochu, McGill University, Montréal, QC, Canada; A. L. Moran, United States Naval Academy, Annapolis, MD; T. Addona, n-WERKZ, Ile des Soeurs, QC, Canada
A commercially viable means of processing nanostructured MCrAlY powder has been developed, applied, and tested for thermal barrier coating (TBC) application. The new approach does not use liquid nitrogen, which has previously been the primary means of processing similar nanostructured metal powders and which is cost-prohibitive for many commercial applications. In addition, the new approach offers the advantage of reduced processing time as compared to cryomilling. MCrAlY coating samples with and without YPSZ top coats were produced using conventional thermal spray processes, i.e., HVOF and APS. Preliminary results from static oxidation and thermal cycling tests show clear advantages over their counterpart coatings. Compared to thermal spray coatings using conventional NiCrAlY bond coats, the nanostructured bond coat samples showed delayed formation of mixed oxide thermally grown oxide (TGO) and the TBC samples resulted in a 50% improvement in thermal cycles to failure. Failure analysis of the thermal cycled samples validate this.
Summary: Very recent advancements in processing nanostructured metal powders without the use of liquid nitrogen holds much promise for the application of nanostructured MCrAlYs (and other metals) for commercial applications. Nanostructured MCrAlY coatings with and without YPSZ top coats show unique and attractive features, when compared to their conventional counterpart coatings. Reduction in overall TGO growth rate and the propensity towards delayed formation of mixed oxides has been identified as key attributes associated with the coating's nanostructure. This has led to the notable improvement in thermal cycling performance of TBCs with nanostructured MCrAlY coatings.
