Measurement of the particle temperature and velocity in detonation spraying is significantly complicated by the pulsed character of the process. In the present study, these parameters are measured for powders with strongly different nature and properties such as WC/Co, Inox and Ti. Experiments are performed using an original computer-controlled detonation spraying (CCDS) installation developed by the authors. The system is distinguished by the mode of powder feeding into the gun barrel which is pulsed in time and localized in space. Evolution of the particle-in-flight velocity and size is examined by an original CCD-camera-based diagnostic tool developed by the authors. A significant spatial separation of the particles along the detonation plume is observed during their acceleration: 15 μm fine particles overtake 45 μm coarse particles by more than 10 plume diameters. For this reason, distributed scanning over the plume length is applied in order to obtain adequate results. A previously developed mathematical model of the process is experimentally validated. Calculations are found to be in a qualitative agreement with the experimental results. As far as particle-in-flight velocity is concerned, the agreement is even quantitative.

Cold and detonation spraying methods are based on the interaction of high-velocity particles with substrate. High quality coatings from various powder materials can be deposited. In both processes, the substrate experiences insignificant thermal effect. Thermally sensitive powder can be sprayed with no oxidation and decomposition. The initial powder microstructure and even nanostructure can be preserved under properly selected spraying conditions. This study is based on a comparative analysis of the mechanical, electrical, and heat transfer properties of a series of coatings deposited by cold and detonation spraying technologies. The coatings are produced from copper and aluminum powders using a commercial Cold Spray equipment CGT-4000 and an original computer-controlled detonation spraying (CCDS) installation developed by the authors. The coating microhardness, density, electrical and heat conductivity, adhesion, cohesion, etc. are measured and compared. Particular advantages and drawbacks of both spraying methods are discussed.

This study investigates the influence of spraying distance and substrate orientation on the formation of metallic coatings by detonation spraying. Deposition efficiency was determined for aluminum, copper, titanium, and steel powders sprayed at different distances on substrates oriented at different angles. The results show that detonation products maintain their influence on sprayed particles even outside the barrel despite the pulsed nature of the detonation spraying process. Numerical calculations of particle acceleration and heating inside the barrel are performed for several materials and a theory of the processes outside the barrel is proposed. Optimal spraying parameters allowing 60-80% deposition efficiency are defined and experimentally validated for the materials studied.

Laser assisted direct metal deposition (or simply DMD) belongs to the family of laser cladding. This is flexible and efficient method for elaboration of diverse coatings including functionally graded, multi-layered, etc. The coatings are characterized by excellent adhesion (metallurgical contact), low porosity and variable thickness up to several millimeters and even centimeters. Actually DMD technology is under intensive development. The most important objective is to increase product quality, process stability and reproducibility along with the simultaneous decrease of risks, failures and defects both on processes and on end-products. The use of the TRUMPF 505 DMD machine with 5 kW CO 2 laser allowed to scale-up the technology to an industrial level. The targeted applications are related to petrol, chemical and plastics industries where wear resistance is improved by deposition of a hard-phase coating; in aeronautics DMD is used for near net shape manufacturing from Inconel alloys.