Effects of spark plasma sintering treatment for cold-sprayed metallic coatings

Spark plasma sintering (SPS) is a pressure-sintering technique that employs a large pulsed direct current (DC). The SPS is expected to improve the adhesion strength between particles without causing excessive growth of refined crystal grains for cold-sprayed metallic coatings. In order to investigate the effects of SPS, cold-sprayed Cu coatings were treated by both the SPS and an annealing heat treatment (AHT) under a wide range of temperatures. The microstructures and mechanical properties of the treated specimens were investigated primarily by scanning electron microscope observations, electron backscatter diffraction analyses, hardness tests, and tensile tests. The microstructural properties of the SPS specimens treated at 300°C, such as porosity, crystal grain size distribution, and distribution of plastic strain, were close to those of the AHT specimens treated at 400°C. Moreover, the hardnesses of the SPS specimen and the AHT specimen were in the same range. However, in spite of these results, the tensile strength of the SPS specimen was obviously higher than that of the AHT specimen, which is likely to be caused by the improvement in adhesion strength between particles under the SPS. From these results, it was found that SPS treatment at lower temperatures than that employed in AHT is effective for improving the mechanical properties of cold-sprayed Cu coatings.