High Strain Rate Deformation Phenomena in Explosive Powder Compaction and Cold Gas Spraying

Abstract

Abstract In cold gas spraying, the powder is not molten before impact on the substrate. The bonding of the coating only depends on powder characteristics and impact conditions. To optimize coating microstructure and properties, spray conditions have to be tuned for a particular powder. The optimization procedure usually requires a systematic variation of spray conditions and an analysis of the sprayed coatings which is time consuming and costly. Therefore, alternative test methods which are less expensive and operate with similar load mechanisms on powder particles have to be developed. High strain rate deformation can be easily studied by explosive powder compaction. In this method, the powder is loaded by a shock wave and deformed under high strain rates. The bonding conditions of powder particles should be similar to those obtained in cold spraying. By a special design, shock loading in explosive powder compaction can cover a wide energy range in one single experiment. Therefore, the method appears feasible to determine the energy input required for successful bonding of particles. To evaluate the capability of the method, microstructural features of particle/particle interfaces are investigated and compared to those of cold sprayed coatings. In addition, the results can supply more information concerning the bonding mechanisms in cold gas spraying.