Abstract
By use of up-to-date methods of gaseous detonation spraying it is possible to obtain coatings with wide range of thermal and kinetic energy of sprayed particles and their state (liquid, solid, semiliquid, with change of their chemical and phase composition duration of stay in impulse hot gaseous detonation jet, etc.). The philosophy of gas detonation sprayed coating structure and properties control include next basic methods: (1) change of values and ratio of thermal and kinetic energy of sprayed particles; (2) governing of thickness and sizes of single layers of coating (“coating spot“), D-Gun rate of fire, and relative velocity of moving of D-Gun and workpart; (3) change of dispersion and shape of powder particles; (4) regulation of thermal cycle of coating in process of spraying by use preliminary, concomitant or post spraying heating or cooling; (5) use of variable spraying modes for obtaining of individual layers and zones of coating (change of composition and flow rate of gases and powder, D-Gun fire rate, powder dispersion, distance of spraying, etc.); (6) settlement of ratio between percentage of amorphous, microcrystalline and crystalline phases, metastable and equilibrium phases by selection of rational conditions of spraying; (7) control of degree of physico-chemical transformations into powder particles (polymorphic transformations, dissociation, oxidation, interaction between components of composite powders, etc.), change of time of particles stay into gas products flow, composition and parameters of gaseous medium, etc.; (8) alloying of sprayed powders as for assurance of necessary properties of coatings as for improvement of their inclination to coating formation (oxidation resistance into high temperature gas flow, inclination of seizure, etc.); (9) use of composite powders; (10) spraying at mode with powder particles which have premelting temperature at time of coating formation; (11) treatment of sprayed coatings (thermal, thermo-chemical, thermo-mechanical, etc.); (12) control of coating macrostructure by successive deposition of layers, bands and spots of coatings with smooth or abrupt change of composition, deposition of discrete coatings; etc. Abstract only; no full-text paper available.
