Effects of titanium and boron alloying with non-equimolar AlCrNbSiTi high entropy alloy nitride coatings

• Published in: Surface & coatings technology 2024-04, Vol.482, p.130709, Article 130709
• Main Authors: Moirangthem, Igamcha, Wang, Chaur-Jeng, Lou, Bih-Show, Rahmadtulloh, Ismail, Tiwari, Krishnakant, Lee, Jyh-Wei
• Format: Article
• Language: English
• Subjects: AlCrNbSiTiN; High entropy alloy coatings; Nanoindentation; Superimposed HiPIMS-MF; TiB2
• ISSN: 0257-8972; 1879-3347
• DOI: 10.1016/j.surfcoat.2024.130709

Among various fabrication technologies for high entropy alloy coatings, high power impulse magnetron sputtering (HiPIMS) technologies have been utilized to synthesize dense microstructure and high hardness coatings with enhanced mechanical and chemical properties. Mid-frequency (MF) pulses have been introduced in the off-time of HiPIMS pulses of the superimposed HiPIMS-MF system to improve the deposition rate. In this study, AlCrNbSiTiBN coatings were deposited using a superimposed HiPIMS-MF system connected to an Al4Cr2NbSiTi2 high entropy alloy target and a direct current (DC) power source for TiB2 target in a reactive Ar and N2 gas mixture. The DC power of the TiB2 target was varied to increase the titanium and boron contents. With increasing Ti and B contents, the microstructure transforms from loose granular and crystalline structure to denser and refined nanocrystalline phases. A residual stress-free coating with a B content of 4.2 at.%. and a hardness of 16.2 GPa was achieved without intentional heating and substrate bias. The poor corrosion resistance of the coatings with lower B contents can be enhanced with a further increase of B content up to 6.4 at.% and reaching a maximum of 10.3 times improvement than that of AISI 304 stainless steel. •Six AlCrNbSiTiBN coatings were deposited using a superimposed HiPIMS-MF system.•Increasing Ti ratio and N reduce the lattice parameter.•Coating structure changes from granular to dense nanocrystalline with increasing B content.•Coating with (Ti+B)/(Al+Cr+Nb+Si) ratio of 0.47 exhibits a hardness of 16.2 GPa.•Coating with (Ti+B)/(Al+Cr+Nb+Si) ratio of 0.58 shows the best corrosion resistance, 10.3 times of AISI 304 steel.