Study of high-temperature oxidation resistance of M(Cr30W5C1.5) alloys.

The research is devoted to the study of high-temperature oxidation resistance of multi-component alloys of the system M(Cr30W5C1,5), where the matrix base (M) is a combination of elements Co, Fe, Ni, Al and Mn, and in addition, they contain 30 wt. % Cr, 5 wt.% W and 1.5 wt.% C: AlCoNiFe(Cr30W5C1,5), Al2CoNiFe(Cr30W5C1,5), MnCoNiFe(Cr30W5C1,5), CoNiFe(Cr30W5C1,5), Co(Cr30W5C1,5), Ni(Cr30W5C1,5) and Fe(Cr30W5C1,5). The relevance of the work is due to the search for alternatives to traditional Co-baltochrome alloys (stellite), the use of which, despite the high level of useful characteristics, is limited due to high cost. The purpose of the study was to determine the influence of matrix composition on the oxidation kinetics during heating in an air environment. The research methodology included alloy synthesis by vacuum melting, confirmation of the composition and microstructure of the samples (scanning electron microscopy, X-ray diffraction), and thermogravimetric analysis of the behavior of the obtained samples when heated from room temperature to 1300 °C. The results showed that the temperature threshold for the onset of accelerated oxidation for all alloys is in the range of 1000–1100 °C and depends on the matrix composition. AlCoNiFe(Cr30W5C1.5) and Fe(Cr30W5C1.5) systems showed the highest threshold temperatures. The composition of the studied samples promotes the formation of protective oxide layers (Cr2O3 and Al2O3 in systems with aluminum) and suppression of the growth of undesirable phases, which is confirmed by the data of X-ray phase analysis and microstructural studies. It is shown that up to the threshold temperatures of accelerated oxidation the stability of the studied compositions to oxidation in air is lower or is of the same order with the sample composition corresponding to the composition of Stellite 6. The results obtained in the course of the work confirm the prospectivity of multicomponent alloys based on high-entropy alloys for application in mechanical engineering, power engineering and aircraft construction.