Deriving Velocity and Temperature During Cold Spray Deposition with Infrared Thermography

Cold spray deposition is increasingly used for repair and advanced manufacturing, with coating quality strongly dependent on particle impact velocity and temperature. While techniques for measuring in-flight particle velocity are mature, quantitative in-flight particle temperature measurement remains challenging due to micron-scale particle size, supersonic speeds, and low emitted radiance. High-sensitivity mid-wave infrared (MWIR) cameras enable radiometric temperature measurements at microsecond exposure times. We present an infrared thermography methodology to derive particle velocity and radiometric temperature during deposition using high-sensitivity MWIR imaging.

Two test scenarios illustrate this point and are compared. In the first scenario, a Telops FAST M3k equipped with a G1X microscope lens captured particle streaks at microsecond exposure times. Dedicated cold spray analysis software detected individual streaks, estimated particle trajectories, and computed time-resolved velocity and temperature. Measured velocities exhibited a stable mean across the acquisition, indicating consistent spray conditions, while the derived temperature range aligned with expectations based on process settings. In the second scenario, a Telops FAST M3sHD capable of achieving nanosecond exposure time, with a G1X lens enabled higher-definition measurements during deposition. The larger focal plane array and shorter exposure time reduced motion blur, yielding shorter streaks closer to true particle dimensions. This supports more robust characterization of particles, particle speeds, and accurately derived temperatures.

Together, these results demonstrate the ability of MWIR thermography to provide quantitative, time-resolved particle velocity and temperature measurements during cold spray deposition, supporting both research and operational monitoring. This approach offers a practical pathway toward the advanced physical understanding of particle characteristics and real-time process monitoring.