Microstructure control in WCrTi medium-entropy alloy coatings by HiPIMS-induced ionization

Tungsten-containing medium-entropy alloys show a combination of good mechanical properties, corrosion, and thermal resistance, making them promising candidates for demanding applications. To overcome production challenges and reduce costs, the deposition of coatings is a useful strategy. This study therefore explores the synthesis of near-equimolar WCrTi Medium-entropy alloy (MEA) coatings using magnetron sputtering techniques. By changing the operating mode from direct current to high power impulse magnetron sputtering (HiPIMS) and bipolar HiPIMS, the sputtered species ionization fraction and their energetic bombardment are controlled. The effect of these plasma characteristics on the coatings structural and morphological properties is detailed. HiPIMS promotes a single bcc crystalline structure without requiring post-deposition thermal treatments. Energetic ion bombardment refines the microstructure and favors an oriented crystalline growth but, when excessive, introduces partial amorphization. These findings demonstrate the feasibility of producing W-containing MEA coatings for extreme environments using advanced sputtering techniques.