Nauka i Tehnika (Aug 2014)
INVESTIGATION OF PROCESSES ON TREATMENT OF PLASMA COATINGS MADE OF MATERIALS BASED ON MULTIFUNCTIONAL OXIDE CERAMICS WITH LASER IRRADIATION IMPULSES
Abstract
The purpose of the presented paper is to optimize technological parameters of hardening high-energy processing used for sprayed coatings made of materials based on oxide ceramics with inclusions of solid lubricant. The paper presents results of the investigations on influence of power density and total number of laser irradiation impulses in a spot treatment on thickness of treated coating layers made of materials based on oxide ceramics. The considered wear-resistant coatings require increased cohesive and adhesive strength. Therefore, the total number of impulses should ensure melting and sealing of the coatings along the whole thickness that will fully contribute to obtain hardened nano-crystalline and amorphous structures.The work is based on complex metallography, X-ray diffraction and electron-microscopic investigations on modified structural elements of composite coatings being treated with highly concentrated energy sources. The following main processes of hardened plasma coating formations have been revealed in the paper: com paction of sprayed materials due to thermal and shock-wave impacts of laser irradiation impulses. In this case material porosity is decreasing, cohesive and adhesive strength of coatings is increasing, grain structure is crushed, amorphous and nano-crystalline phases of higher strength are formed all these facts are evidenced by an increase in average micro-hardness of deposited compositions. Duration of thermal laser irradiation impulse impact on the material is sufficient to activate chemical processes in the boundaries of main phases of the composite coating. This leads to formation of finely dispersed (including nanoparticle size) compounds that strengthen boundaries of the main phases and the coating as a whole. This is confirmed by the results of an X-ray diffraction analysis.
