Effects of M 2 CO 3 (M = Li,Na,K) on electrolytic boronising of titanium in Na 2 B 4 O 7 melts

Abstract

The effect of M₂CO₃ (M = Li, Na, K) on electrolytic boronising of titanium in Na₂B₄O₇–20M₂CO₃ was investigated. The phase composition of boride was determined by X-ray diffraction. The morphology of boride was determined by scanning electron microscopy, and the composition of boride was measured by X-ray energy dispersive spectroscopy. The results show that the boride layer comprised TiB₂ and TiB. TiB₂ presented a dense phase, whereas TiB presented whiskers. TiB₂ became thicker in the order of Li₂CO₃, Na₂CO₃ and K₂CO₃, in the melts. Simultaneously, TiB whiskers gradually changed from short and thick to long and thin. This change was due to the different polarisation abilities of alkali metal ions in M₂CO₃ (M = Li, Na, K).