By: P.P. Shukla and J. Lawrence

Wolfson School of Mechanical and Manufacturing Engineering, Loughborough University,
Leicestershire, LE11 3TU, United Kingdom

Ceramics have a wide usage in the engineering sector. Various applications in the aerospace and
automotive industry extensively use ceramics due to their desirable mechanical and thermal properties
in comparison to metal and metallic alloys. Commercial advantages offered by laser systems such as
high speeds, shorter processing times, accuracy, and deep penetrating treatment are attractive in
comparison with conventional processing techniques. Processing of engineering ceramics from
employing industrial lasers can be an asset to manufacturers by achieving reduced lead times,
production cost, faster delivery and achieving better tolerances. Laser processing can be a superior
technique applicable to engineering ceramics such as glazing for improving the surface finish,
aesthetics and enhancing the ceramics (component) functional life, providing that the effects of the
laser/ceramic material interaction are better understood.
Surface treatment by means of fibre laser radiation using various processing gas compositions was
conducted on cold isostatic pressed silicon nitride and zirconia engineering ceramics to observe
changes in their surface integrity, chemical composition and distribution of the heat affected zone. The
as received and fibre laser treated surface topography was measured in 3D using white-light
interferometry. Scanning electron microscopy was then used to observe the microstructural integrity
prior to and after the fibre laser treatment. Energy dispersive X-ray was employed thereafter to detect
the change in the chemical composition.
Laser surface treatment softened the treated zone specifically with silicon nitride and increased in
hardness within the interface and the respected untreated areas. The highest material removal for
silicon nitride ceramics was achieved using the oxygen gas. However, a change in the materials
topography resulted in the silicon nitride ceramic being much courser. Argon and nitrogen resulted in
producing the finest surface finish with a lower material removal in comparison with the sample treated
by oxygen. Although, nitrogen showed a significantly modified surface in comparison to the results of
other gases used. Investigation into thermal and microstructural analysis is further being undertaken for
both ceramics.
The surface topography of the fibre laser treated zirconia ceramics was considerably different to that of
the silicon nitride ceramics due to both materials comprising of different microstructure structures,
thermal properties and their effects during laser processing. The surface melting and solidification of
zirconia occurs at lower temperatures compared to silicon nitride ceramics. To create a sufficient
melted zone and to redistribute the surface; higher laser power is required which on the other hand, has
the tendency to produce cracks in to zirconia due to the thermal shocks induced. This was why zirconia
ceramic was processed using lower power opposed to silicon nitride for locally melting and
redistributing the melt zone. From this, the grain boundaries had began to connect and bind into each
other particularly using argon and oxygen. Using argon produced one of the finer surface finish and
lower material removal. It can be concluded that the fibre laser treatment using argon would be most
effective for surface treating and modification of zirconia based engineering ceramics

The above brief overview was extracted from its original abstract and paper presented at The International Congress on Applications of Lasers & Electro-Optics (ICALEO) in Orlando, FL. To order a copy of the complete proceedings from this conference click here

(Paper 204)