Sri Lankan corundum as an industrial material

Ramani Kangaraarachchi

W A Geethapriya, a student of the pioneer batch of the Uva Wellassa University, who graduated recently with a Bachelor of Technology degree, tested erosive wear resistance of Sri Lankan corundum for his final year research project.

Geethapriya

He has revealed through this research that Sri Lankan natural corundum specimens are comparable or even better in wear resistance than the commercially available synthetic corundum. As non-precious corundum is abundantly produced in gem mines of Sri Lanka, this study will possibly open industrial opportunities for these relatively cheaper but better wear resistive materials.

Sri Lankan corundum has been famous all over the world as precious gemstones like ruby and sapphire for several centuries. However industrial use of non-precious Sri Lankan corundum has not been tried so far on a commercial scale. Corundum is a naturally occurring oxide of alumina (Al2O3). In Moh’s hardness scale it is only one unit below diamond, the hardest mineral.

Due to its hardness corundum also finds use in mortars, wire drawing dies, thread guides and gauge blocks. In industries it is valued mostly for its abrasive property. Corundum is also refractory, the melting point being 2010§C and hence it is used in a sintered form in the manufacture of special refractory crucibles, rods and other materials.

The expected high erosive wear resistance of corundum, which qualifies it for industrial applications, motivated Geethapriya to investigate its tribological properties to test the feasibility before selecting it as an industrial material. Tribology is the science and technology of interacting surfaces in relative motion.

Corundum

It includes the study and application of the principles of friction, lubrication and wear. The damage to a solid surface by progressive loss of material due to relative motion between the surfaces and a contacting substance is referred as wear. Slurry erosive wear resistance of corundum provides important clues of their suitability for potential industrial uses.

Geethapriya conducted a set of experiments using Sri Lankan natural corundum extracted from gem gravels in different parts of the country. Synthetic corundum, which is commercially available and widely used in industrial applications, but relatively expensive, was also used in this investigation to assess the viability of natural corundum as an industrial material against the synthetic counterpart.

He constructed a slurry pot tester where silicon carbide particles suspended in distilled water were used as the erodent. This simple and low-cost instrument provided him with a smart tool to test the erosion of the corundum specimens as a function of time comparing that with the synthetic corundum.