Kablov

This article deals with the results of a thermodynamic analysis of nitrides phase state, their quantity in the alloy HA30-VI when the quantity of nitrogen varies in the initial furnace-charge at different melting stages. Thermodynamic calculations allow to estimate the phase composition of liquid melt and crystal nickel alloy HA30-VI. It was investigated whether titanium nitride, hafnium and carbides in equilibrium conditions were part of that alloy. Minimal permissible quantity of nitrogen required to eliminate the formation of nitrides was calculated.

Nitrogen behavior under different thermo-time modes of the melting alloy HA30-VI in the induction furnace was investigated; optimal temperature of melted nitrogen depuration was determined. The negative influence of nitrogen on the formation of parasitic grains with random orientation near the surface of mono-crystal casting was shown. Non-uniform distribution of nitrogen with the height of cast mono-crystals was determined.

The authors study the influence of nitrogen on the form of primary carbides in charge intermediates of alloy GS 30-VI. Metallographic researches of the structure and forms of primary carbides were conducted in initial charge intermediates with various impurity content of nitrogen. It was established that with the increase of nitrogen content from 0,0004-0,0008% to 0,0015-0,0035% carbide morphology acquires a rounded or polyhedral form instead of laminar. The authors present the dependence between the impurity nitrogen content in the heat-resisting alloy and the quality of produced single-crystals. The authors propose a formation mechanism of primary carbides of various morphology during melt solidification.