Nitridation of Titanium-Tin Alloys during Heating in Air

摘要

The scaling behavior of titanium alloys containing Sn up to 20 mass% in air at 1373 K was investigated. The Ti-Sn alloys were prepared by arc melting furnace. Four layers were detected in the scale formed on the alloys; i.e., TiO_2, TiO, nitride and Sn-rich layers. The nitride phase consisted of stoichiometric titanium nitride (TiN) and finely dispersed metallic tin. The TiO phase was formed by the oxidation reaction of TiN in the nitride phase. The Sn-rich phase was formed at the interface between the TiO_2 phase and the base alloy in the initial stage of heating, and then the rapid nitridation reaction occurred at the interface between the TiO_2 layer and the Sn-rich layer. The formation of the Sn-rich layer consisted of liquid tin and Ti_6Sn_5 seemed to be essentially needed for the nitride formation. The rate controlling process of the rapid nitridation reaction was considered to be the transport of titanium through the Sn-rich phase.