Influence of porous high entropy alloy coating on wetting behavior and interfacial microstructure of Al-Si alloy on steel substrate

A porous FeCoNiCr high entropy alloy (HEA) coating was prepared on steel substrate via vacuum sintering. Wetting behavior of liquid Al-12Si alloy over coated and uncoated steel substrate was comparatively analyzed. The results show that the liquid Al-12Si alloy droplets were quickly spread and infiltrated into the porous structures under the enhanced capillary force by the micro-channels in the porous coating. A complete wetting ~ 0° contact angle (CA) was thus achieved; however, the CA was up to 41.2° in the case of uncoated steel substrate. In the case of uncoated steel substrate, the interfacial microstructure consisted of θ-Al13Fe4, η-Al5Fe2 and τ1-Al2Fe3Si3, while it changed to Cr-enriched FCC, AlFe-enriched BCC and AlNi-enriched B2 +Al-enriched BCC eutectic-like structure embedding in the HEA skeleton. The suppression of the formation of intermetallic compounds (IMCs) at the interface was mainly attributed to the sluggish diffusion and HEA effects of the porous coating. The altered interfacial metallurgical reactions and the enhanced capillary force were contributed to the improvement of wettability. This research provides a new method for improving the wettability and suppressing the interfacial IMCs in reactive metallic wetting systems.