Controllable sinking electrical discharge machining performance of dendritic-structured W-containing refractory high-entropy alloys

W-containing refractory high-entropy alloys (RHEAs) are promising for elevated-temperature applications, while the complexity of dendritic microstructure poses challenges in achieving controllable machining performance. In this work, the controllability of sinking electrical discharge machining (EDM) performance on dendritic-structured (TiVCr)₉₅W₅ and (FeVCr)₉₅W₅ RHEAs was evaluated using a mathematical model that expresses the relationship between discharge parameters and machining performance. A superior controllability of the material removal rate and surface roughness (Ra) was obtained by the high accuracy and good predictability of the model, with the R² value close to 1 and a predicted error for Ra below 5%. This was attributed to the stable removal behavior of the dendritic microstructure. Melting was the primary removal mechanism for both dendrites and inter-dendrites. The W element can stabilize the removal behavior of constituent elements. No obvious compositional variation was observed within the crater formed in dendrites. As more W diffused into inter-dendrites, the variation of Cr and V in inter-dendrites reduced from approximately 20.0% to less than 2.0%. Similar melting removal mechanisms led to an analogous relationship between the machining performance and processing conditions of the two RHEAs. Compared to the relatively high surface roughness achieved by wire-EDM, the optimized Ra values of 0.329 and 0.728 μm for (TiVCr)₉₅W₅ and (FeVCr)₉₅W₅, respectively, demonstrated the superiority of sinking EDM for RHEAs. The present findings have confirmed the superior controllable sinking EDM performance for W-containing RHEAs, providing useful guidance for the processing of W-containing RHEAs in practical applications.