Cold gas spraying (CGS) is a coating technique, in which solid particles are accelerated to supersonic speed in a low temperature gas jet, typically Nitrogen or Helium, to the surface of a component. Exceeding sufficiently high velocities upon impact, the high-strain-rate deformation of particles leads to adiabatic shear instabilities at interfaces with the substrate or already deposited coating layer. The current study is part of the collaborative project CORE (Computerized Refurbishment) funded by dtec.bw aiming to utilize CGS as an advanced repair technique for industrial applications. The residual stresses developed during the cold spray process play an important role in the performance and mechanical integrity of CGS-repaired parts. In this early stage of the project, main focus is payed to adjusting the CGS process parameters and possible boundary conditions contributing to stresses. In the later stage, these findings should be transferred to the local repair of components.

Here, two different coating systems are investigated: i) Aluminium alloy Al6061 coating on Al6061 substrate material and ii) Ti99.7 coating on Aluminium alloy AlMg3 substrate material. This should allow to study influences of different material combinations and of different CGS process parameters on the residual stress state development.

For residual stress analyses, two methods are considered i.e. incremental hole drilling and X-ray diffraction. Both approaches are appropriate for analysing local residual stress depth distributions. Results of both approaches are compared for the above-mentioned coating systems. The residual stress analysis is complemented by metallographic investigations, surface topography measurements, hardness measurements and determination of effective elastic constants by means of ultrasonic phase spectroscopy to assess the coating quality and microstructure.