To address the challenge of sealing clearance control in high-performance aero-engine compressors, this study developed a novel CoCrAlY-hBN-PHB abradable seal coating system for Ti 2AlNb components operating at ~650 °C. The work systematically investigated the effects of hBN (5–15 wt%) and PHB (2–10 wt%) content on the microstructure and high-speed tribological performance of coatings. The results demonstrate that coating hardness could be effectively tailored through composition design, but excessive hBN (>10 wt%) reduced deposition efficiency and induced anomalous hardening in the 15hBN + 10PHB coating due to in-situ compaction effects. Coating hardness was inversely correlated with abradability. Although the softest 10hBN + 10PHB coating exhibited optimal abradability, its excessively high interconnected porosity could compromise structural integrity and corrosion resistance. Tribological analysis revealed that the superior temperature rise rate of the blade tip caused preferential heat accumulation, generating localized temperatures exceeding 1072 °C that triggered B2 phase transformation and material transfer to the coating via microwelding. Concurrently, work hardening of the coating surface further degraded abradability and increased blade wear. The 15hBN + 6PHB composition was identified as the most balanced formulation, though further improvements by architectural grading, hBN/PHB distribution optimization, and blade tip thermal protection are necessary for practical application. This work elucidates the critical thermo-mechanical coupling mechanisms governing Ti 2AlNb/coating interactions and provides essential insights for designing next-generation abradable seal coating system.