Microstructure control in WCrTi medium-entropy alloy coatings by HiPIMS-induced ionization
摘要
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.
Graphical AbstractMicrostructure (top-left panel) and morphology (bottom panel) of near-equimolar WCrTi films obtained by magnetronco-sputtering. Specifically, the W cathode was operated in direct current magnetron sputtering, high power impulse magnetron sputtering (HiPIMS) and bipolar HiPIMS with 50 V, 200 V, and 300 V of positive voltage. The top-right panel shows the W cathode HiPIMS and bipolar HiPIMS current and voltage waveforms. The Cr and Ti cathodes were operated in direct current magnetron sputtering in all cases.