Application of AlB$_{12}$–Al Electric Spark Coatings to Protect Titanium Alloys During Wear Under Fretting Corrosion

Abstract

The article deals with the study of the possibility of using AlB12-50 wt.% Al aluminium-matrix composite material electric spark (ES) coatings to protect titanium alloys during wear under fretting. Fundamental possibility of such coatings obtaining is estimated by theoretical calculation of Palatnik's criterion (1.22). Thermal conductivity coefficient and heat capacity of the composite were calculated or determined from an experiment. The coatings were deposited on ALIER-52 setup. Fretting corrosion tests were carried out on MFK-1 setup according to 'the coating-counterbody' system (counterbodyhardened Steel 45). Phase composition of the coating was studied with DRON-3M diffractometer and elemental x-ray spectrum analysis of the friction track surface was carried out using a JEOL JAMP9500F (SEM) microanalyzer equipped with an energy-dispersive x-ray microanalysis. The following phases namely TiB2, Ti aluminides, Ti, TiO, TiO2 and AlB10 were revealed by x-ray analysis in the coating. The absence of the AlB12 phase is noteworthy. It can be explained by thermal-oxidative destruction of aluminium dodecaboride under severe conditions of ES alloying (ESA). Regardless of the deposition mode, the wear of the sample with ES-coating is shown to be significantly less than that of the uncoated one. A conclusion is made about the prospect of using this electrode material for ESA of titanium alloys operating