Microstructural study of Co-based superalloys and ODS steels obtained by Spark Plasma Sintering (SPS)
The CINN has collaborated with IMDEA Materiales and the University Carlos III in the microstructural study of Co-based superalloys and ferritic ODS steels consolidated by Spark Plasma Sintering. The results of these studies were presented as oral presentations in the VI edition of the National Congress of Pulvimetallurgy that took place in Ciudad Real (Spain) from 7th to 9th June 2017.
The abstracts of the two lectures given are shown below:
Microstructural study of a group 4 (Y-Al-Ti-Zr) ODS ferritic steel consolidated by Spark Plasma Sintering (SPS).
E.Macía1, J.Cornide1, A-García-Junceda2, L.A. Díaz3, M. Campos1.
1 UNIVERSIDAD CARLOS III
2 IMDEA Materiales
3 CENTRO DE INVESTIGACIÓN EN NANOMATERIALES Y NANOTECNOLOGIA (CINN)
Oxide Dispersion Strengthened (ODS) ferritic Steels are extraordinary candidates for nuclear applications due to their good behavior at high temperature and under irradiation conditions .ODS ferritic steel was produced by mechanical alloying and SPS to obtain a complex nanostructure. A four group elements (Y-Ti-Al-Zr) was selected to improve the stability of the precipitates since they are the main responsible for the thermal stability of fine structure. The heterogeneous distribution of stored energy due to the high energy attrition of MA powder will produce an inhomogeneous recrystallization during the consolidation step. After SPS consolidation a heterogeneous grain size distribution was attained, as recrystallization depends on the plastic deformation degree, on the composition of each particle and on the oxide dispersion promoted. Therefore sintering cycle was performed at 1373 K following fast heating rates (from 100 to 600 °C/min) to minimize porosity. The final microstructures were characterized by XRD and electron microscopy (SEM and TEM). In addition, Vickers microhardness and tensile tests was performed to analyze the mechanical response at R.T.
Microstructural study of Co-9Al-9W alloys produced by SPS with Ti and Ta as alloying elementsEstudio microestructural de aleaciones de Co-9Al-9W producidas por SPS con Ti y Ta como aleantes
Marta Cartón-Cordero1 , Mónica Campos2 , Eric Macia-Rodríguez2 , Luis Antonio Díaz, 3 Jesús Cano-Cabello2 , Andrea García-Junceda1 , José M. Torralba2
1 IMDEA Materiales
2 UNIVERSIDAD CARLOS III
3 CENTRO DE INVESTIGACIÓN EN NANOMATERIALES Y NANOTECNOLOGIA
Co-based superalloys with ϒ-ϒ dual phase microstructure are considered a good alternative for high temperature in extreme environmental conditions applications due to their good strength, wear behavior and high oxidation resistance. In this work a fully prealloyed gas atomized powder with the nominal composition of Co-9Al-9W (at%) has been used. With the aim of promoting the ϒ´ phase precipitate, 2 at% of Ti and 2 at% of Ta have been added through mechanical alloying to the original powder. In order to reach a high level of densification maintaining an ultrafine grain size in the microstructure, the powder has been consolidated through Spark Plasma Sintering (SPS). The ϒ´ phase precipitate is obtained after subsequent heat treatments, first a solution treatment and then aging. By X ray diffraction (XRD) technique and scanning and transmission electron microscopy (SEM/TEM), the structural and microstructural changes produced after the heat treatments from the as obtained material have been monitored. The addition of Ti and Ta to the base alloy improves the ϒ’ phase precipitation process, and also affect to its thermal stability, improving the high temperature performance of the alloy. To characterize this influence on the ϒ´solution temperature, a thermo-gravimetric analysis has been performed for different compositions and heat treatments.