Titanium Matrix Composite Ti/TiN Produced by Diode Laser Gas Nitriding

A high power direct diode laser, emitting in the range of near infrared radiation at wavelength 808-940 nm, was applied to produce a titanium matrix composite on a surface layer of titanium alloy Ti6Al4V by laser surface gas nitriding. The nitrided surface layers were produced as single stringer bea...

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Bibliographic Details
Published in:Metals (Basel ) 2015-01, Vol.5 (1), p.54-69
Main Author: Lisiecki, Aleksander
Format: Article
Language:English
Subjects:
Aluminum
Chemical vapor deposition
composite
Dendritic structure
Diode lasers
Infrared lasers
Investigations
Laser beams
laser gas nitriding
laser surface treatment
Lasers
Metal matrix composites
Metals
Microhardness
Near infrared radiation
Nitriding
Nitrogen
Radiation
Residual stress
Semiconductor lasers
Solidification
Surface layer
Surface layers
Titanium
Titanium alloys
Titanium base alloys
Titanium nitride
titanium nitrides
Wear resistance
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Summary:A high power direct diode laser, emitting in the range of near infrared radiation at wavelength 808-940 nm, was applied to produce a titanium matrix composite on a surface layer of titanium alloy Ti6Al4V by laser surface gas nitriding. The nitrided surface layers were produced as single stringer beads at different heat inputs, different scanning speeds, and different powers of laser beam. The influence of laser nitriding parameters on the quality, shape, and morphology of the surface layers was investigated. It was found that the nitrided surface layers consist of titanium nitride precipitations mainly in the form of dendrites embedded in the titanium alloy matrix. The titanium nitrides are produced as a result of the reaction between molten Ti and gaseous nitrogen. Solidification and subsequent growth of the TiN dendrites takes place to a large extent at the interface of the molten Ti and the nitrogen gas atmosphere. The direction of TiN dendrites growth is perpendicular to the surface of molten Ti. The roughness of the surface layers depends strongly on the heat input of laser nitriding and can be precisely controlled. In spite of high microhardness up to 2400 HV0.2, the surface layers are crack free.
ISSN:2075-4701
2075-4701
DOI:10.3390/met5010054