Puhachevska Y. Development of composite materials and coatings on the base of titanium-chromium diboride for wear-resistance improvement of titanium alloys in conditions of fretting - corrosion

Thesis is devoted to the development of TiCrB2-(Ni-Cr) composite materials, determination of optimal parameters of plating ESA - coatings by electrodes on the TBHN composites base and research of structure-phase composition influence on tribological properties. The conducted researches of titanium alloys wear mechanism have allowed formulating criteria of material composition choosing at operation in conditions of fretting-corrosion. It is developed the new composite material TiCrB2-(Ni-Cr) on the bases of these principals. It is made choice of metallic bound optimal composition - Nі - 15 mass % Cr on the base of established regularities of wetting and contact interaction TiCrB2 with nickel and its alloys. The three compositions of materials with 30, 40, 50 mass % of metallic bound are developed. The composite materials of TiCrB2 - (Ni - Cr) system have heterophase structure from nickel-chromium matrix with gradually distributed grains of titanium - chromium diboride. During friction process on material surface the discrete oxide films have created due to selective oxidation of refractory and metallic components of composite with formation of compound titanium and chromium oxides (oxides of refractory component) and compound nickel and chromium oxides (oxides of metallic bound) which operate as protective preventing raised wear of material. The discrete film which forms on refractory component of composite is a operative, so the highest wear-resistance has composite with 30 mass % of bound. Due to realization of oxidizing wear mechanism composite materials have high wear-resistance which exceeds wear-resistance of titanium alloys in 2 - 4 times. As a result of titanium alloy electric spark-alloying by TBHN electrodes on its surface have formed coatings which consist of modifying layer, saturated by refractory component 0,5 mkm and zones with titanium - chromium diboride conglomerates 3 - 4 mkm. Such coatings increase wear-resistance of titanium alloys ВТ-3 and ВТ-22 in 2 - 4 times.