Smoothing and Structural Hardening of the Additive Surface of the TiZrNb Alloy by Electric Spark Treatment with an AlCaZrY Electrode

The conditions of healing of surface defects and structural strengthening of additive surface of Ti-ZrNb samples obtained by selective laser melting (SLM) with subsequent vacuum electric spark treatment (EST) by low-melting AlCaZrY electrode were investigated. The effect of electrode polarity on kinetics of mass transfer, structure, chemical and phase composition of modified surface was studied. The investigations were performed by methods of scanning electron microscopy, energy-dispersive spectroscopy and optical profilometry. It is shown that the use of the optimal mode of EST reduces the roughness of the additive surface by 3 times as a result of local melting of protrusions and filling of cavities up to 200 μm deep with the melt formed in-situ during the EST process. It is found that the structure of such a coating consists of an aluminum matrix strengthened by dispersed intermetallic inclusions Ti3Al with a size of about 4 μm. The applied treatment made it possible to increase the wear resistance of the TiZrNb alloy against a steel ball by 2 times, and also to reduce the friction coefficient from 0.37 to 0.29.