Dovgal A. Regularities of structure formation of new wear-proof composition materials based on system SiC-Al2O3 and coatings made of them for face sealing com-pressions

Degree thesis is about the development of new composition materials and coat-ings made of the system SiC-Al2O3 with enhanced wear resistance. In order to im-prove the properties of this system the following researches have been held: investiga-tion of effect of double-component oxide bound of Al2O3 and ZrO2 in eutectic content on the technological modes of acquisition, structure and properties of composition ma-terial; introduction of metallic bound in the system SiC-Al2O3 to enable the coating deposition of gas-flame techniques: acquisition of metallic constituent in form of the millings within the batch mixture of SiC-Al2O3 ingredients and investigation of its amount effect on the content, structure and properties of composition material. Application of two component oxide bound with eutectic content of Al2O3 and ZrO2 enables substantial decreasing of hot-pressing temperature that results in forming of high-dense fine-grain composition materials. Friction of these composition materials together with steel counterbody has the oxidative wear mechanism, material SIAL-Z (5,8 microns per kilometer) has the best wear resistance. During the wear tests together with ceramic counterbody abrasive wear mechanism takes place, at that I=4,7 microns per kilometer. On the ground of contact interaction research of the system SiC-Al2O3 with nickel and alloys of Ni-Al, optimal contents for coating with wear proof constituent SiC-Al2O3 have been chosen. The coatings are presumed to be deposited by gas-flame methods. In particular, high-velocity air fuel method has been used. The structure of HVAF-coating of (SiC-50% Al2O3)-50%(Ni-15% Al) is heterophase, consists of SiC-Al2O3 ceramic material grains of size 7-10 microns and its separate components surrounded by the nickel-aluminium bound. Wear rate of developed coatings is 30 microns per kilometer. It is twice less than the wear rate of hardened uncoated steel. It has been established, that wear process of HVAF-coatings of the system (SiC-50%Al2O3)-50%(Ni-15%Al) has the prevailing oxidative wear mechanism. In order to create the metal ceramic materials, effect of iron millings on the tech-nological modes of acquisition of ceramic materials of the system SiC-Al2O3, their structure and properties have been researched. Tribological performances of acquired materials have been tested. Wear rate of these materials together with the steel coun-terbody is 3,8 microns per kilometer, and together with ceramic counterbody it is 4,1 microns per kilometer. In both cases oxidative wear mechanism takes place.