Combinatorial Materials Research for the Development of New Advanced CoNi-Base Superalloys

Nanomechanical testing methods are very well suited to complement combinatorial materials researchCombinatorial materials research using diffusion couplesDiffusion couple. Diffusion couplesDiffusion couple allow the investigation of the microstructureMicrostructure and the mechanical propertiesMechanical properties of multiple alloy compositions in a single sample without the need to cast many different alloys. To expand the investigation of mechanical propertiesMechanical properties on diffusion couplesDiffusion couple to higher temperatures, indentation creepIndentation creep is a highly suitable technique. In this work, the diffusion coupleDiffusion couple approach was utilized in combination with a high-temperatureHigh temperature indentation creepIndentation creep testing technique, using a 25 µm flat-punch indenter, to conduct combinatorial investigations on a Co–Ni diffusion coupleDiffusion couple and on a multinary γ/γ′ CoNiCr-base superalloySuperalloys diffusion coupleDiffusion couple with increasing Cr content. For the Co–Ni system, the highest room temperature hardness and highest creep resistanceCreep resistance at 550 °C was observed between 50 at.% Co and 80 at.% Co. For the γ/γ′ CoNiCr-base superalloySuperalloys CoWAlloy2, an optimum Cr content of 14 at.% has been found. Up to this Cr content the hardness and creep resistanceCreep resistance is not altered and the precipitationPrecipitation of undesired phases does not occur. With further increasing Cr content, the γ′ volume fraction decreases significantly and undesired W- and Al-rich phases precipitatePrecipitates, leading to an increase in hardness but a deterioration of the creep propertiesCreep properties.