ARCHIVES of FOUNDRY ENGINEERING Published quarterly as the organ of the Foundry Commission of the Polish Academy of Sciences ISSN (1897-3310) Volume 7 Issue 1/2007 147 – 152 32/1 Influence of gas detonation spraying conditions on the quality of Fe-Al intermetallic protective coatings C. Senderowski, Z. Bojar, W. Przetakiewicz Department of Advanced Materials and Technologies, Military University of Technology, Kaliskiego 2, 00-908 Warsaw, Poland *: e-mail: csenderowski@wat.edu.pl Received 08.02.2007; Approved for print on: 12.03.2007 Abstract The aim of this paper is to present generalized research results and analyses of the quality of coatings produced with self decomposing Fe-Al intermetallic powders deposited on 1045 steel in the gas detonation spraying (GDS). A number of GDS experiments has been carried out with significantly changed operational spraying parameters (the volume of the fuel gas, carrier gas, distance and the frequency of spraying) which define the process energy level directly influencing the quality of the coating. On the basis of the initial results the choice of the process parameters has been made to obtain the most advantageous set of geometrical and physical-mechanical properties of the coating material and substrate. The quality of the coatings was considered by taking into account the grain morphology, chemical content, phase inhomogeneity, cohesive porosity, as well as adhesive porosity in the substrate coating joint. The coating roughness was also considered. It was found that all GDS coatings produced are built with lamellar splats which result from the GDS process transformed (changed plasticity and geometry) powder particles forming the deposit. The result of the GDS spraying parameters optimization is the lack of signs of melting of the material (even in microareas) while the geometry of the deposited grains is considerably changed. This phenomenon has been considered as a proof of high plasticity of the GDS formed Fe-Al intermetallic coatings. Key words: Gas detonation spraying of coatings; Protective coatings, Fe-Al intermetallics. 1. Introduction During the analysis of the GDS process it has been found that the GDS Fe-Al intermetallic technique offers practically unlimited possibilities of spray parameters as well as coating chemical composition control and is very promising in that the coatings produced show unique properties (i.e. high abrasion, erosion and corrosion resistance, resistance to high temperatures and thermal shocks, good adhesion and low porosity) [1]. The essence of GDS is the use of the energy of the gas mixture blast to heat and relay high kinetic energy to the particles of the powdered coating material [2]. GDS deposited coatings are formed through the collision with a substrate material and deformation of the small grains of the powder which, together with the detonation products, create metallic spray. The energy source of the bonds between the deposited powder, substrate and coating layers is high kinetic energy as well as low thermal energy accumulated in the two-phase metallic spray [3]. The characteristic lamellar structure of the GDS coatings is a result of impulsive deformation of the Fe-Al intermetallic powders and promotes formation of inhomogenous multiphase (composite) structure of the coatings. The research results from the WAT database show that this technique brings advantageous effects during both in ‘in situ’ coating deposition (pure elements powder spraying) [4], and in spraying of the powders produced in advance and powdered intermetallic phases [5-9]. However, although the ARCHIVES of FOUNDRY ENGINEERING Volume 7, Issue 1/2007, 147-152 147