Numerous efforts have been carried out over the years to improve process control in the thermal spray industry. Among those, the need for online monitoring of the thickness of the coating is unquestionable as it leads directly to better uniformity, less powder usage and increased productivity. In 2006, a new technology based on 3D profiling has been adapted to the thermal spraying environment and has shown conclusive results for online real-time monitoring of the thickness of single layers as they were being sprayed. A micron level resolution was achieved independently of the process, the powder and the thermal effects related to thermal spraying. In this paper, we present the latest results from early industrial implementations. New applications of this technology for substrate geometries with increased complexity are also investigated.

In the past ten years, significant progress has been made in the field of advanced sensors for particle and spray plume characterization. However, there are very few commercially available technologies for online characterization of the as-deposited coatings. In particular, coating thickness is one of the most important parameter to monitor and control. Current methods such as destructive tests or direct mechanical measurements can cause significant production downtime. This paper presents a novel approach that enables online, real-time and non-contact measurement of individual spray pass thickness during deposition. Micron-level resolution was achieved on various coatings and substrate materials. The precision has been shown to be independent from surface roughness or thermal expansion. Results obtained on typical HVOF and plasma sprayed coatings are presented. Finally, current fields of application, technical limitations and future developments are discussed.