Titano-Aluminizing of Nickel based Super-Alloys

Abstract

The experimental researches aimed to find a way how to increase the percentage of γ’-Ni3(Al, Ti) phase in the superficial layers of the nickel base super-alloys, particularly of the INCONEL 738 super-alloy and also to determine the thermodynamic stability conditions of this strengthening phase by ensuring an over-unity Al wt%/Ti wt% ratio in these layers. The chosen solution was to realize a simultaneous Al-Ti cementation (TitanoAluminizing) using solid powdery media containing TiO2 and Al powder as active suppliers of Ti and Al. Besides these components, in the cementation media there are, or not, other components which participate actively in the reduction of TiO2 such as fluoride and magnesium powder. These components have as role the dispersing/blocking of the sintering tendency of the mixture components. In the mixture, there are also components which have as role cleaning/activation of the surfaces subject to thermochemical processing. The experimental results led to the conclusion that the Al wt%/Ti wt% ratio can be widely modified, but with keeping of it over-unity, by means of rigorous control of solid powdery media phases composition, such as to ensure that the strengthening phase γ’-Ni3 (Al, Ti) is existent and stable in the superficial zone of the simultaneous cemented layers.