Strive for energy efficiency, due to the concerns about climate changes and sustainable use of natural resources, requires new approaches in material design and processing. The use of emerging additive manufacturing (AM) methods could enable the processing of advanced materials in complex shapes with large material and cost savings as well as effective recycling strategies. For high-temperature applications there is a big demand on novel materials with superior mechanical properties as well as oxidation and wear resistance. High Entropy Alloys (HEAs) represent one of the promissing group of such materials, showing a high potential for being the next generation high-temperature materials [1,2].

The calphad technique has been already established as an essential tool for screening of new HEAs. In the current study a combinatorial approach for simulation-aided design of promissing compositions with high throughput screening technique were utilized in order to explore the CrCoFeNi-system with additions of

Al (3 to 15 at.-%) and Ti (3 to 9 at.-%). The proposed design concept aims for a microstructure consisting of fcc matrix and ordered bcc B2 with gamma’ precipitations under condition of sigma-free compositional range. For the laser powder deposition an in-house developed COAXshield powder nozzle was utilized enabling the monitoring of the whole cladding process while providing Ar gas-shielding to protect the powder and the molten material against oxidation. Both pre-alloyed powders and mixtures of element powders were used and in situ mixed to achieve the desired alloy compositions. As built and heat treated (HT) conditions were thoroughly analyzed by means of scanning electron microscopy (SEM), including advanced EDS and EBSD techniques. Furthermore, micro-hardness measurement was used to evaluate the mechanical properties of the new designed alloys.

It could be shown that the performed calphad simulations by means of ThermoCalc software allow a fast and effective prescreening of the investigated compositional system. For the HT at temperature T = 1077 °C for

t = 24 h the predicted phase compositions are in good agreement with experimental data obtained from SEM analysis. The prcipitation hardening behavior of the explored HEA-system should be further thoroughly investigatated in order to achieve a desired optimal microstructure with advanced mechanical properties.

Literature

[1] S. Praveen, H. S. Kim, High-Entropy Alloys: Potential Candidates for High-Temperature Applications – An Overview, Adv. Eng. Mater. 2018, 20, https://doi.org/10.1002/adem.201700645.

[2] S. Gorsse, D. B. Miracle, O. N. Senkov, Mapping the world of complex concentrated alloys, Acta Materialia 2017, 135, 177, https://doi.org/10.1016/j.actamat.2017.06.027.