Structure, Stacking Faults, and Electrochemical Behavior of α-Ta Obtained By Chemical Vapor Deposition

Abstract

Stacking faults in tantalum deposited in a helium environment on a copper substrate by chemical vapor deposition and their effect on the protective properties are studied using X-ray diffraction, scanning electron microscopy, glow-discharge emission spectroscopy, electrochemistry, and strength assessment. It is shown that the probability of the formation of stacking faults in deposited body-centered cubic (bcc) tantalum in the {112} planes is a sensitive parameter with respect to the deposition conditions (temperature and helium content). With an increase in the helium concentration from high to medium values, the sum of probabilities of the formation of deformation (α) and twinning (β) stacking faults 1.5α + β in α-Ta increases five times (from 0.025 to 0.13%), and with a decrease in temperature from 800 to 750°C, the sum of probabilities increases 35 times (from 0.025 to 0.89%). A decrease in the probability of stacking faults in deposited α-Ta tantalum is related to a significant increase in the corrosion resistance and adhesion strength of the coating to the substrate. A mechanism for the formation of metastable hexagonal close packed (hcp) phases of tantalum on stacking faults in α-Ta in the {112} planes is proposed.