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Corrosion behaviour of hardfacing alloys used in the mining industry

Nguyen, Vu Tran (2015). Corrosion behaviour of hardfacing alloys used in the mining industry. Bachelor of Engineering (4th Year Project) Thesis, Charles Darwin University.

Document type: Thesis
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Author Nguyen, Vu Tran
Title Corrosion behaviour of hardfacing alloys used in the mining industry
Institution Charles Darwin University
Publication Date 2015
Thesis Type Bachelor of Engineering (4th Year Project)
0912 - Materials Engineering
Abstract In practice wear resistance is an important requirement for equipment and structures typically in mining, metallurgical and power industries. A common method that is extensively used to provide wear resistant is hardfacing. The method is to deposit harder materials on the base metal by welding processes. The deposited materials form a layer on the surface of the cheaper core material and improve wear resistance performance.

Most of the hardfacing materials are based on carbide of chromium. While research has been done on improving the wear resistance of these alloys, there is little attention to the corrosion resistance of these materials despite that fact that they are exposed to corrosive environments. For example, hardfacing materials expose to highly corrosive medium such as alumina processing or acidic sugar cane juice in sugar cane industry are reported to be corroded.

In this thesis, four different commercial hardfacing electrodes with different chemical compositions will be used to produce a diverse MxCy stoichiometry and a number of different microstructures. Electrochemical anodic polarisations and potentiostatic test were conducted in highly caustic solution of 2M NaOH at pH above 14. It was found that there were little differences in the corrosion resistance with the additions of other alloying elements. Importantly, microstructure examination after the test showed that the carbides were preferential to be corroded comparing to the matrix when the potential is increased, which contradicts to the results of other research in the literature. The use of Pourbaix diagrams suggests a possible explanation for this behaviour.
Keyword hardfacing alloys
corrosion resistance
wear resistance
metal carbides
carbide dissolutions
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Created: Wed, 15 Jul 2015, 09:49:34 CST by Jessie Ng