Surface characterization and compositional evaluation of a fibre laser processed silicon nitride (Si3N4) engineering ceramic

Shukla, Pratik and Lawrence, Jonathan (2010) Surface characterization and compositional evaluation of a fibre laser processed silicon nitride (Si3N4) engineering ceramic. Lasers in Engineering, 20 (5-6). 359 -370. ISSN 0898-1507

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Abstract

Fibre laser surface treatment of a cold isostatic pressed (CIP) Si3N4 engineering ceramic was performed using various processing gas compositions to observe the changes on and within the surface of the engineering ceramic; in particular, surface topography, material removal, chemical composition, surface hardness and distribution of the heat affected zone (HAZ). Surface melting and distribution of the melt zone were found with all fibre laser radiated samples, as well as surface finish and the material removal varying with changes in the gas composition. Fibre laser processing of the Si3N4 with N2 assist gas proved to be the most effective combination for effecting micro-structural changes as small sized elongated grains were found as a result of the faster cooling rate. Consequently, O2, ambient air and compressed air produced considerable amount of morphological changes. This was found to be due to de-composition, material removal of the upper most surface layer and the Si3N4 ceramic’s interaction with the assist gas compositions and the atmosphere at elevated temperatures. Maximum material removal was found when O2 assist gas was employed, taking in account of the O2 generating an exothermic reaction and consequently excessive heating. The compositional analysis revealed a chemical change occurring within all fibre laser radiated surfaces of the Si3N4 engineering ceramic as fibre laser radiated Si3N4 was transformed to SiO2.

Keywords:Fibre laser, Si3N4 engineering ceramic, processing gases, material removal, surface finish, chemical composition
Subjects:J Technologies > J300 Ceramics and Glasses
J Technologies > J310 Ceramics
F Physical Sciences > F361 Laser Physics
Divisions:College of Science > School of Engineering
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ID Code:9221
Deposited On:29 Apr 2013 16:09

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