## 4 Economic Efficiency of High-Entropy Coatings  
According to [PERSON] et al. [15], the corrosive, erosive and abrasive effects of the geothermal steam were researched at Hellisheioi geothermal power plant in Iceland, where currently there are seven in-work geothermal turbines. Due to the very aggressive environment created by the geothermal steam chemical composition, temperature, pressure and abrasive particles [16], the maintenance costs for the geothermal turbine can go as high as USD 20 mil for an operating period of 15-20 years [17]. The main costs are represented by the turbine blades' replacement and turbine transportation for refurbishing, but also the downtime necessary for the mentioned reasons [15], which can lead to a cost of approx. USD 190,000/turbine/year. The main concerns regarding the high-entropy alloys are represented by the costs when comparing them with the commercial alloys and materials used currently for components or equipment parts. In order to reduce costs while benefiting from the superior properties of these materials, coating the in-work equipment was proposed as an alternative, viable solution. Due to the direct contact of the turbine blades with the geothermal steam, by depositing HEA on the leading edge, the corrosion-erosion effect could be reduced. According to the data published by [PERSON] et al. [19], the standard dimensions for the next-generation low-pressure geothermal steam turbine blades range from 348 mm to 789 mm for 50 Hz and from 290 mm to 665 mm for 60 Hz. There are usually 90 blades on the last row of the rotor, in the area of low-pressure steam, resulting in high replacement costs [20]. Figure 3: Mapping and EDS analyses results for the HEA coating. For replacing a carbon steel single turbine blade, the price is approx. USD 1.344 according to the India Mart website [21]. By considering the mentioned data, the cost calculation for coating a single blade was performed, where material and labor costs were included. The raw, pure (approx. 99.5%) elemental metallic powder materials were purchased from Laboratorium(r) Company, and the prices for the necessary quantity to produce 100 g of the high-entropy alloy material are presented in Table 2.  
The mechanical alloying processing cost for producing 100 g of the high-entropy alloy, processed in Fritch Pulverisette 6 Mono mill is presented in Table 3. To the processing costs, the price of the process control agent (PCA) was added. For milling 100 g of high-entropy alloy, 2 wt% N-Heptane was used. After obtaining the alloyed powder, samples were consolidated by pressing and sintering. For the pressing process, the costs were low and they were added to the other costs section in the final calculation. The calculation of economic efficiency also included the material loss resulted from the ball milling process, which was estimated at 3%. For the sintering process, the costs are presented in Table 4.  
The furnace sintering process was performed under an argon atmosphere, with a gas flow of 2 L/min, purchased from Linde(r), with a purity of 99.99% and a price of USD/L 0.01. The samples were sintered for 360 min in a sintering furnace, which resulted in a total argon cost of USD 7.42. After adding the costs of the argon to the sintering process costs, this resulted a total of USD 11.06 per batch of HEA samples. After the samples were consolidated and mechanically processed into electrodes, multiple successive layers of the high-entropy alloy were deposited on the stainless steel substrate. The calculations were performed for the standard coating applicator, which is often used to cover large areas in a shorter time. Working time and related costs for coating an area of 100 \(\times\) 100 \(\times\) 0.05 mm with CoCrFeNiMo\({}_{0.85}\) HEA are shown in Table 5.