Traitement de trempe martensitique par laser

Perspectives ouvertes par l'optimisation et le contrôle

Future prospect of the laser transformation hardening of surfaces by the optimization and the control of the treatments

¹ INSA GEMPPM, Calfetmat. Villeurbanne
² PSA Études et Recherches, DRAS, Centre SAMM, Bièvres
³ Groupe d'Etudes Appliquées au Laser, Institut de Technologie de Kunming, Chine

Abstract

In the first part we demonstrated our capability to increase the efficiency between laser beam and material with an absorbing coating that is reproducible and which nature and thickness are perfectly controlled. More an optical device leading to the transformation of repartition laser beam permitted us to decrease the space-time fluctuations of the energy repartition in the beam and to obtain not only hardened tracks with modulated geometries but also the treatment of sample geometries hard to be treted with classical technics. In order to release ourselves of the instability of laser emission power we realized a servo-control of this power.

In the second part we showed that an analytical model as original as simple in relation with a judicious but physical and « real time » measure (surface temperature) should permit us to believe to a control of the laser process and to a real implantation of this particular type of treatment in the industry world. We applied our knowledge, in the last part, to the treatment of notched fatigue specimens. We increased the fatigue limit of the whole specimen in regard with base material. The phenomenon was explained in term of compression residual stresses in the hardened tracks.