Influence of Pt/Ru ratios on the oxidation mechanism of MCrAlYTa coatings modified with Pt-Ru overlays

TL;DR

This study examines how varying Pt/Ru ratios in NiCoCrAlYTa coatings affect oxidation mechanisms, revealing that higher Pt improves oxidation resistance by forming a denser alumina layer, while increased Ru leads to microcracks and oxide development.

Contribution

It provides new insights into how Pt/Ru ratios influence oxide layer formation and oxidation resistance, guiding cost-effective coating design through microstructural optimization.

Findings

Higher Pt content enhances alumina layer density and oxidation resistance.

Increased Ru content causes microcracks and oxide development in TGO.

Optimized Pt/Ru ratios can improve coating performance and reduce costs.

Abstract

This study investigates the influence of varying Pt/Ru ratios on the oxidation mechanism of NiCoCrAlYTa coatings with electrodeposited, vacuum-annealed Ptsingle bondRu overlays. Weight change measurements, scanning electron microscopy/energy dispersive X-ray spectrometry (SEM/EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) were used for high-temperature oxidation analyses, showing superior resistance with higher Pt contents. This was attributed to the creation of a denser, thinner, and more homogeneous layer of alumina (alpha-Al2O3) in the thermally-grown oxide (TGO) layer. On the contrary, an increase in Ru contents led to the development of other oxides and microcracks along with alumina in the TGO layer, undermining oxidation protection. The accommodation of Ti and Ta, in the minimally-deteriorative form of carbide, along with Y into the TGO layer with increasing Pt contents further enhanced oxidation resistance. In addition to the explored significant impact of the Pt/Ru ratio on oxide scale characteristics and oxidation resistance, the lower cost of Ru compared to Pt suggests the potential for designing cost-effective systems through optimized Pt/Ru ratios and microstructural engineering.