Application of the laser spallation technique to the measurement of the adhesion strength of tungsten carbide coatings on superalloy substrates

Laboratoire de Combustion et de Détonique (UPR 9028 du CNRS), ENSMA, BP 40109, 86961 Futuroscope Chasseneuil Cedex, France

Corresponding authors: boustie@lcd.ensma.fr eric.auroux@free.fr Romain@ensma.fr

Received: 5 June 2000
Revised: 7 September 2000
Accepted: 18 September 2000
Published online: 15 October 2000

Abstract

High power pulsed lasers are used to induce shock waves in Hastelloy X targets coated with tungsten carbide of 70 μm and 50 μm thickness. In suitable irradiation conditions, a debonding of the substrate/coating interface due to the generation of tensile stresses is observed. Experimental results are analyzed with the use of numerical simulations yielding the stress history at interface and its dependence on laser pulse intensity up to 600 GW/cm² with 1 ns and 3 ns durations under direct irradiation, and 23 ns with water confinement. As a consequence of shock decay during the propagation through the substrate, a strong variation of incident intensity results in a small variation of tensile stress. This allows an accurate determination of the debonding threshold which is found in the range of 1.0 to 1.3 GPa for short laser pulses (1 and 3 ns) and 0.5 to 0.6 GPa for long laser pulses (23 ns confined).