Liquid-phase hydrothermal deposition of MoS2 into TiAl coatings on Ti6Al4V alloy

Abstract

Antifriction layers on the Ti6Al4V alloy were obtained by creating a developed structure of lubricant pockets with dry self-lubricating substances. In this work, the structure and tribological behavior of TiAl intermetallic coatings after hydrothermal deposition of MoS 2 were studied. Coatings of titanium aluminides with a regular crack network were obtained by a Ti6Al4V alloy electrospark treatment in an equimolar mixture of titanium and aluminum granules . The etching in HF solutions significantly increases the crack width (from 0.77 to 4.8 μm). The liquid-phase hydrothermal synthesis was used to fill the cracks acting lubricant pockets in the coatings with MoS 2 . It was shown that a molybdenum disulfide layer consisting of spherical particles with a diameter of 3.09 ± 0.63 μm formed on the surface of the samples filling the cracks as a result of hydrothermal synthesis. The results of tribotechnical tests showed that the hydrothermal deposition of MoS 2 on TiAl coatings reduces their friction coefficient to 0.29 and the wear rate by 5.4 times. Cu-plating protects TiAl-layer during etching, increasing the capacity of lubricant pockets. Such treatment reduces wear rate and friction coefficient to 0.17. Lubricant working lifetime was 61 times longer on Cu-plated and etched TiAl coating than on Ti6Al4V polished surface. Studies have shown the promise of hydrothermal deposition of MoS 2 on the Cu-plated and etched TiAl coatings to improve tribological properties of the Ti6Al4V alloy. • TiAl/MoS 2 coating was prepared by ESD, Cu-plating, etching and hydrothermal coat. • The etching by HF acid converts the TiAl coating cracks into lubricant pockets. • The MoS2 presents in etched TiAl coating cracks after hydrothermal treatment. • The etching and MoS 2 deposition reduce COF of the TiAl coating from 0.97 to 0.29. • Cu-plating before etching increase the lubricant lifetime of TiAl/MoS 2 coating.