Intermetallic protective coatings on titanium

In the presented work, the powder siliconizing and liquid phase alloying were used for a surface hardening of titanium and to protect titanium against high-temperature oxidation. The powder siliconizing was carried out in a pure Si powder at 900–1100 °C/3–48 h and the liquid phase alloying was realized in an Al–20 wt.% Si melt at 800 °C/5–40 min. It was shown that the coating methods produced hard multi-phase surface layers composed of various kinds of silicides (Ti5Si3, Ti3Si and TiSi) and ternary Ti(AlXSi1−X)2 (τ2) phase. The binary silicide layers grew in accordance with the parabolic law while the ternary layer grew very rapidly. It was shown that the powder siliconizing at 900–1100 °C/3 h produced sufficiently thick and compact protective layers. The liquid phase alloying at 800 °C/10 min was efficient for preparation of protective layers. The oxidation experiments were conducted at 850 °C in air. Both the powder siliconized and liquid phase alloyed coatings were shown to provide a good protection against high-temperature oxidation.