Comparison of Microstructure and Phase Composition of Vacuum Induction Ti-48Al-2Cr-2Nb Alloy Melted in Crucibles with Plasma Spraying Coatings

摘要

The chemical and phase composition as well as the microstructure of γ-TiAl based alloys vacuum induction melted in ceramic crucibles with protective plasma spraying coatings have been investigated. The coatings made of ZrO_2·Y_2O_3, ZrO_2·CaO and SrZrO_3 on graphite and silicon carbides crucibles were used. In each crucible 3 to 7 melts (one by one) were earned out. It was concluded that from the ingots' microstructure, phase and chemical composition point of view the best results were obtained for SrZrO_3 coating on SiC crucible. It was found that the specimens made of the first and second ingots melted in the same crucible charcterized lamellar two phase γ+α_2 microstructure. In the third and next ingots Ti_2AlC carbides and precipitations of Ti_5Si_3 type occured.