Cantor and Yeh were the first who suggested that the conventional alloying strategy has been very restrictive with respect to the whole range of possible materials and suggested the new alloy concept of high entropy alloys (HEA). HEA consist of five or more principal elements in equimolar or near equimolar ratios, each element having concentrations between 5 and 35 at. % with simple crystal structures such as fcc, bcc or hcp. The most prominent representative the so called “Cantor alloy” CrMnFeCoNi is usually synthesized using the widely adopted melting and casting route. The present contribution investigates the possibilities to use additive manufacturing (AM) by means of laser cladding to build up coatings of this alloy on a matrix made of a regular structural material. The major objective is to explore how the synthesis route influence the structure and properties of CrMnFeCoNi in the as cladded and the heat treated condition.
In the current work the two methods laser powder and laser wire deposition were applied to build up coatings of CrMnFeCoNi. For the laser powder deposition an in-house developed COAX4.0 powder nozzle is utilized allowing the monitoring of the whole cladding process. Both pre alloyed powders and mixtures of element powders were used and compared with respect to cost and processability as well as homogeneity, oxide contamination and composition of the coatings. The laser wire deposition used a so-called COAXwire nozzle and a laboratory-fabricated wire of the cantor alloy with a diameter of 0.6 mm for the cladding process. Metallography, micro-hardness measurements and advanced scanning electron microscopy including EDS and EBSD were used to analyze the differently synthesized coatings.
It can be shown that both, laser powder deposition with pre alloyed powder and laser wire deposition is capable of generating coatings of single phase fcc CrMnFeCoNi possessing high chemical and structural homogeneity without macroscopic segregations and only containing a small amounts of impurities. Although the processing by laser powder deposition with mixtures of elemental powders is more difficult and requires more optimizing it proved to be the most flexible way of enabling in-situ variations in composition.