This paper deals with an adhesion test of coatings using laser-driven shock waves. Physical aspects concerning laser–matter interaction, shock wave propagation and interface fracture strength are described. This comprehensive approach using two numerical codes (HUGO and SHYLAC) allows the determination of mechanisms responsible for coating debonding and a quantitative evaluation of fracture strength. From this description, a coating test protocol is also designed. To diagnose coating debonding, it is based on the analysis of experimental rear free surface velocity profiles measured by velocity interferometer system for any reflectors (VISAR). Ni electrolytic coating (70–90 µm) deposited on a Cu substrate (120–190 µm) is used for the experimental validation of the test. The fracture strength is 1.49 ± 0.01 GPa for a laser pulse duration of 10 ns at 1.064 µm.

Spallation of materials induced by laser driven shock waves is generally produced under uniaxial (one-dimensional (1D)) deformation by irradiating a spot of diameter much greater than the sample thickness. Here, two-dimensional (2D) effects are introduced in shock wave propagation by drastically reducing the loaded spot. Experiments performed on aluminium samples detect the effect of lateral wave propagation, both on recovered samples and on time-resolved VISAR measurements. Damage zones are localized completely differently from that under uniaxial condition, according to the presence of 2D effects, and the signature of these 2D effects can be read on VISAR signals. Numerical simulations provide a full understanding of wave propagation and resulting damage in 1D or 2D configuration. Comparisons with experimental VISAR signals show the possibility of validating more accurately the dynamic damage criteria, including the 2D effects.

No abstract

Coating-substrate adhesion in cold spray is a paramount property, the mechanisms of which are not yet well elucidated. To go into these mechanisms, due to the intrinsic characteristics of the cold spray process (particle low-temperature and high velocity) direct observation and control of inflight particles and related phenomena cannot be done easily. For this reason, an experimental simulation of the particle-substrate reactions at the particle impingement was developed. This simulation is based on original flier impact experiments from laser shock acceleration. Relevant interaction phenomena were featured and studied as a function of shearing, plastic deformation, phase transformation primarily. These phenomena were shown to be similar to those involved in cold spray. This was ascertained by the study of the Cu-Al metallurgically reactive system using SEM, TEM, EPMA, and energy balance and diffusion calculations. This simulation could also be used to feed finite element modeling of cold spray and laser shock flier impact.

International audienceThe aim of this study was to compare three adhesion tests carried out on plasma-sprayed copper coatings on aluminium substrates. The first test, the bond pull test, designated EN 582 or ASTM C633, involves a uniaxial static stress and is commonly used in the coating industry. The second test, the LASAT (LASer Adhesion Test), is a recently developed technique based on spallation phenomenon due to laser induced shock waves. In this test, the coating delamination results from spallation at the coating/substrate interface due to uniaxial tensile stress. The last test, the bulge and blister test, involves a quasi-static measurement of the crack propagation energy at the coating/substrate interface. These three techniques have been used to evaluate the influences of different process parameters involved in the coating adhesion such as aluminium surface roughness, substrate pre-heating and plasma spray conditions