The infrared thermography control of the laser welding of amourphous polymers

International audienceIn laser welding technique, a real-time control of temperature distribution inside the irradiated materials is essential when attempting to optimize the process. For all laser welding methods that operate by the transmission principle, the difficulty of recording the developed temperature at the interface derives from the fact that materials to be welded are in contact throughout the entire process. In the present study, in order to overcome this issue, a contact-free method such the infrared thermography is used for surface temperature measurement. Corroborating this data with a numerical simulation of the temperature field evolution inside the components, an assessment of optimal process parameters is possible. The experimental investigations are made on amorphous polymers, in a typical configuration for through-transmission laser welding. The fine agreement obtained between the experimentally and calculated data, validate the infrared thermography as a non-destructive method for real-time monitoring of the welding process

LASER CLADDING ON ALUMINIUM BASE ALLOYS

laser cladding is often performed on iron or titanium base alloys. In the present work, this method is employed on aluminum alloys ; nickel or silicon are added by powder injection. Addition of silicon leads to sound surface layers, but with moderated properties, while the presence of nickel induces the formation of hard intermetallic compounds and then to an attractive hardening phenomena ; however a recovery treatment has to be carried out, in order to eliminate porosity in the near surface region

SURFACE TREATMENTS BY Cw YAG LASER

The feasability of surface treatments by cw YAG laser has been established. Concerning solid phasis treatment, we explored superficial quenching of grey cast iron. It brings out that it's no necessar to precoat the sample before treatment, the natural absorptivity is suffisant. Concerning liquid phasis transformation two examples are presented : surface alloying and cladding. For the first one, the power required for a given melted depth is 2 times lower than for a CO2 beam. Concerning the second example, it appears that the use of a step index fiber could ameliorate obtained results. Finally from a metalurgical point of view, obtained structures are the same than with a CO2 beam

Study of surface layers and ejected powder formed by oxidation of titanium substrates with a pulsed Nd:YAG laser beam.

International audienceLaser treatment of a titaniumsurface at certain conditions initiates the formation of titanium oxide layers as well as micro (nano) scale powder ejected from the surface of the substrate. The resultant morphology of the surface as well as the size and the structure of the particles are all strongly dependent on the treatment parameters (laser fluence, pulse frequency, overlap parameter, etc.). In this study, titanium substrates were treated with an industrial pulsed Nd:YAG laser in air, with varying parameters. Surface layers and ejectedmaterials were compared using scanning and transmission electron microscopy, X-ray diffraction and Raman spectroscopy. The rutile phase of TiO2 dominates in the surface layers, while the ejected powder is mainly formed of anatase nanoparticles