Effect of TiB2 Content on the Microstructure, Hardness, and Erosive and Sliding Wear Resistance of Arc-Melted Al0.7CoCrFeNiTi0.2 High-Entropy Alloy

The effect of nominal TiB 2 additions (0 to 30 vol pct) on the microstructure, hardness, sliding wear, and solid-particle erosion resistance of arc-melted Al 0.7 CoCrFeNiTi 0.2 high-entropy alloy was investigated. X-ray diffraction showed a predominantly FCC matrix with a minor BCC/B2 contribution, while distinct TiB 2 reflections were observed only for the 30 vol pct material. SEM–EDS revealed increasingly pronounced Ti- and B-rich segregation with increasing TiB 2 addition and coarse plate-like TiB 2 particles at 30 vol pct. Hardness increased from 457 HV 5 for the reference alloy to a maximum of 663 HV 5 at 15 vol pct TiB 2 , then decreased to 574 HV 5 at 30 vol pct. Sliding wear resistance improved markedly up to 15 vol pct TiB 2 , for which the specific wear rate decreased by approximately 82 pct and the coefficient of friction reached its minimum. In contrast, the best solid-particle erosion resistance at 90 deg impingement was obtained at 5 vol pct TiB 2 , with approximately 38 pct lower volume loss than the reference alloy. Higher nominal TiB 2 additions increased erosion loss despite higher hardness. The results demonstrate that the nominal TiB 2 addition providing the best performance among the investigated compositions depends on the degradation mechanism and is governed by the combined effects of matrix strengthening, reinforcement morphology, microstructural heterogeneity, and impact- or sliding-induced damage.