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

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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.
Original languageEnglish
Pages (from-to)359-370
Number of pages12
JournalLasers in Engineering
Volume 20
Issue number5-6
Publication statusPublished - 28 Feb 2010

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Fiber lasers
Silicon nitride
silicon nitrides
fiber lasers
engineering
ceramics
machining
evaluation
gas composition
Gases
Chemical analysis
Exothermic reactions
compressed air
Compressed air
Surface topography
Heat affected zone
Processing
heat affected zone
exothermic reactions
Surface structure

Cite this

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title = "Surface characterization and compositional evaluation of a fibre laser processed silicon nitride (Si3N4) engineering ceramic",
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 Si3N4ceramic’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.",
author = "Pratik Shukla and Jonathan Lawrence",
year = "2010",
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T1 - Surface characterization and compositional evaluation of a fibre laser processed silicon nitride (Si3N4) engineering ceramic

AU - Shukla, Pratik

AU - Lawrence, Jonathan

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N2 - 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 Si3N4ceramic’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.

AB - 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 Si3N4ceramic’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.

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SN - 0898-1507

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