Detonation spraying is a well-known technology which is applied for deposition of diverse powders, in particular cermets, to form various protective coatings. Actual progress is related to a recently developed technique of computer-controlled detonation spraying and its application in non-traditional domains as development of composite and graded coatings or metallization of plastics. The gas detonation parameters are analyzed to estimate the efficiency of different fuels to vary particle-in-flight velocity and temperature over a broad range thus providing conditions to spray diverse powders. A particle of a given nature and fixed size could be sprayed in a solid state or being strongly overheated above the melting point by variation of the quantity of the explosive gas mixture which is computer-controlled. Particle-inflight velocity and temperature are calculated and compared with jet monitoring by a CCD-camerabased diagnostic tool and experimental data on splats formation.

No abstract

This article is a focused review aimed to describe the potential of the computer-controlled detonation spraying (CCDS) for producing and designing coatings with variable chemical and phase compositions and microstructure and promising properties. The development of the detonation spraying method is briefly analyzed from a historical perspective and the capabilities of the state-of-the art facilities are presented. A key advantage of the CCDS is the possibility of using precisely measured quantities of the explosive gaseous mixtures for each shot of the detonation gun and different oxygen to fuel ratios, which can create spraying environments of different chemical properties—from severely oxidizing to highly reducing. The significance of careful adjustment of the spraying parameters is shown using material systems that are chemically sensitive to the composition of the spraying environment and temperature. Research performed by the authors on CCDS of different materials—metals, ceramics, intermetallics and metal-ceramic composites is reviewed. Novel applications of detonation spraying using the CCDS technology are described.

No abstract

The present work was aimed to demonstrate the possibility of forming Fe66Cr10Nb5B19 metallic glass coatings by detonation spraying and analyze the coating formation process. A partially amorphous Fe66Cr10Nb5B19 powder with particles ranging from 45 µm to 74 µm in diameter was used to deposit coatings on stainless steel substrates. The deposition process was studied for different explosive charges (fractions of the barrel volume filled with an explosive mixture (C2H2 + 1.1O2)). As the explosive charge was increased from 35% to 55%, the content of the crystalline phase in the coatings, as determined from the X-ray diffraction patterns, decreased. Coatings formed at explosive charges of 55–70% contained as little as 1 wt.% of the crystalline phase. In these coatings, nanocrystals in a metallic glass matrix were only rarely found; their presence was confined to some inter-splat boundaries. The particle velocities and temperatures at the exit of the barrel were calculated using a previously developed model. The particle temperatures increased as the explosive charge was increased from 35% to 70%; the particle velocities passed through maxima. The coatings acquire an amorphous structure as the molten particles rapidly solidify on the substrate; cooling rates of the splats were estimated. The Fe66Cr10Nb5B19 metallic glass coatings obtained at explosive changes of 55–60% showed low porosity (0.5–2.5%), high hardness (715–1025 HV), and high bonding strength to the substrate (150 MPa).