There is a major driving force to replace Co as the metallic binder for WC carbide composites due to environmental, ethical and economic factors. One of the principle benefits of Co as a binder for WC is that it “wets” the WC surface very well, ensuring a strong carbide-binder bond for load transfer, which improves the mechanical and wear resistance properties. One method of improving the bonding of other metallic binders to WC would be to form a “rim” of a second carbide around each WC grain, or to dissolve another element into the WC structure to changes its wettability by other metallic binder metals such as Ni or Fe alloys.
This project will consider two different carbide additions to assess their effect on the WC grain structure after spraying and after heat treatment. TiC has a lower Gibbs free energy than WC, meaning that it should be favoured to form during heat treatment. This project will aim to investigate if Ti can be incorporated into the WC structure upon WC reformation, or if it will act as a seed onto which WC grains may grow during heat treatment.
MnC has a “less negative” gibbs free energy of formation than WC, and so should form as a carbide around the periphery of the WC grains – a true “core-rim” structure. IF this does occur, then the carbide-metallic binder interface would then be dictated by the wettability of MnC and not WC, opening the potential for alternative binder systems.
Coatings will be analysed by combined DSC and TGA to determine the energy changes that occur due to compositional developments with heat treatment. Heat treatment trials below and above each characteristic DSC peak will enable ethe change in composition to be determined through XRD/EDS and SEM analysis. Longterm heat treatment (125 hours) at 900°C will enable the coating compositions to reach equilibrium and determine if the concept of TiC/MnC addition was successful in being able to develop the desired phase composition in the coating.
Undergraduate
None
No lab has been assigned to this project