Panashenko V. Structural and phase transformations during wear of spark-deposited and laser-spark composite ZrB2-containing wear-resistant coatings on titanium alloys.

Thesis is devoted to the development of new electrode ZrB2-based materials with LaB6, ZrSi2, SiC, AlN adds for increasing wear resistance of titanium alloys in air to abrasive wear (AW) and fretting corrosion (FC). During spark deposition of coating, globules form on the coating surface. The globules are enriched with ZrB2 and have positive effect on the coating wear resistance. Durability of the spark coatings from AW does not correlate with hard phases total content in electrode/coating material. But it correlates with content of ZrB2, which during tribooxidation forms ZrO2 dispersion strengthened borosilicate phase (BSF) that acts as a solid lubricant. SiC additive into the electrode material increases coatings resistance to AW under high load. Laser fusion (LF) of the spark coating reduces the surface microhardness from 17 GPa to ~9.5 GPa, and its resistance to AW/FC increase by 3.2/2.6 times. In the tribooxidation process the both coatings form nanosized surface layers. In the case of the spark coating, this surface layer consists of BSF that is dispersion strengthened with Ti-Zr dioxides, and the layer consists mainly of hard oxide matrix (HOM), in the case of (ESD+LF)-coating. The alternating scheme of layers in multilayer ESD coating considers wetting of the ceramics and titanium substrate with intermediate layer. Wear resistance of the multilayer ESD coating to FC is 1.7 times higher than WC+3%Co ESD coating, and after its LF is 3.3 times higher.