Motivation

In order to develop alloys for high-temperature applications, a broad property profile needs to be met. While focus is often on high temperature strength and creep resistance, critical properties are mostly oxidation resistance at high and ductility at low tmeperatures including the combination of the two.

Mo-Si-Ti and Cr-Mo-Si alloys were identified in the past that exhibit outstanding oxidation resistance and in contrast to other high refractory element containing alloys specifically against catastrophic oxidation, e.g. "pesting".

Particularly, Cr-Mo-Si is a favorable system, since it shows pesting resistance at 800 °C, oxidation resistance at 1100 °C, and surprisingly ductility in compression from room temperature up to 900 °C. To further characterize these promising Cr-Mo-Si alloys and improve the existing properties, the objective is to investigate the solubility limits of Mo and Si contents to find the alloy composition that ensure resistance against pesting, nitridation and oxidation, while maintaining room temperature ductility. The mechanical behavior (e.g. twin formation, ductility) of homogenized microstructures compared to dendritic microstructure will be analyzed. This also involves analyzing the sample microstructure after compression tests to understand the mechanistic origins of twinning in Cr-Mo-Si solid solution.

Methodology

Alloy Synthesis

• Arc melting
• Homogenization heat treatments

Analysis/Characterization

• Oxidation behavior (e.g. cyclic oxidation tests)
• Mechanical behavior (compression tests)
• Microstructure (BSD, EBSD)
• Crystal structure (XRD)
• Chemical verification (EDS, HCGE, ICP-OES)
• 3D atom probe tomography (APT)

Funding

Graduate school 2561 "Materials Compounds from Composite Materials" by Deutsche Forschungsgemeinschaft