Studies on preparation, characterisation and evaluation of properties of Fe 3Al-based intermetallic alloy of composition Fe–16Al–5.44Cr–1Nb–0.5C

Abstract

Efforts on preparation of iron aluminide-based (Fe 3Al) alloys by various techniques are being explored worldwide in view of their excellent combination of metallurgical properties suitable for high temperature applications. So far no process has yet emerged suitable for its commercial exploitation. In the present investigation, an attempt has been made to prepare Fe 3Al-based alloy (iron aluminide alloy) of composition Fe–16Al–5.44Cr–1Nb–0.5C (wt.%) by non-conventional non-furnace process. The process essentially involves the use of cheap, indigenously available oxides of iron, chromium and niobium for their co-reduction with large excess of aluminium, in presence of carbon under flowing argon atmosphere in a specially designed water cooled copper reactor. The charge composition is judiciously adjusted to fulfil two functions simultaneously. Firstly, to attain the alloy composition and secondly, to utilise exothermicity of the overall reactions for their successful completion. A typical charge constituting Al 10 wt.% over stoichiometric amount, Cr 2O 3 stoichiometric amount, Nb 2O 5 and C, double the requisite theoretical amount and lime (CaO) 10 wt.% of total charge (specific heat, 2930 kJ kg −1) resulted in an alloy of nearly targeted composition with about 98 wt.% yield. The alloy formation by the above technique is substantiated by studies on alloy characterisation with respect to composition, phases and microstructure and property evaluation by strength, hardness, rolling and oxidation resistance to indicate its suitability for high temperature applications.