*2.1. Materials*

In the present study, AlCoCrFeNiTi powder (hereinafter referred to as HEA powder) was prepared by ball milling using equimolar related elemental powders with a size of less than 75 μm as starting materials. Ball milling was conducted with a planetary ball mill (XM-4, Sanxing Instruments Ltd., Xiangtan, China). Both the pots and the balls were made of 304 stainless steel. More details about the ball milling process can be found in our previous study [14]. The powder milled for 30 h was mechanically blended with a commercial atomized Ni60 powder (30–80 μm) with an AlCoCrFeNiTi/Ni60 weight ratio of 7:3. Chemical composition of the Ni60 powder is listed in Table 1.


**Table 1.** Chemical composition of Ni60 powder (wt %).

#### *2.2. Coating Preparation*

316 stainless steel discs with a diameter of 25 mm and a thickness of 8 mm were used as substrates. To increase the coating bonding strength, the substrates were cleared with alcohol and sandblasted with alumina (<1 mm) before coating deposition. Sandblasting was carried out with the following parameters: compressed air pressure (0.50 MPa), blasting time (30 s), blasting angle (90◦). A plasma spraying system (PRAXAIR-3710, Praxair Surface Technologies, Indianapolis, IN, USA) was employed to prepare the HEA/Ni60 coating. Plasma spraying was done with the following parameters: plasma arc power (45 kW), main gas (Ar) pressure (0.41 MPa), secondary gas (N2) pressure (0.45 MPa), powder carrier gas (Ar) pressure (0.28 MPa), rotating speed of powder feeder (0.8 <sup>r</sup>·min−1), spray distance (100 mm), and gun traverse speed (200 mm·s<sup>−</sup>1).
