Investigation of Microstructure and Corrosion Resistance of Ti-Al-V Titanium Alloys Obtained by Spark Plasma Sintering

Aleksey Nokhrin,Vladimir Chuvil’Deev,Pavel Andreev,Ksenia Smetanina,Artem Nazarov,Maksim Boldin,Gleb Shcherbak,Artem Murashov,Mikhail Chegurov,Galina Nagicheva,Mikhail Gryaznov,Sergey Shotin

doi:10.3390/met11060945

Abstract

The research results of the microstructure and corrosion resistance of Ti and Ti-Al-V Russian industrial titanium alloys obtained by spark plasma sintering (SPS) are described. Investigations of the microstructure, phase composition, hardness, tensile strength, electrochemical corrosion resistance and hot salt corrosion of Ti-Al-V titanium alloy specimens were carried out. It was shown that the alloy specimens have a uniform highly dense microstructure and high hardness values. The studied alloys also have high resistance to electrochemical corrosion during tests in acidic aqueous solution causing the intergranular corrosion as well as high resistance to the hot salt corrosion. The assumption that the high hardness of the alloys as well as the differences in the corrosion resistance of the central and lateral parts of the specimens are due to the diffusion of carbon from the graphite mold into the specimen surface was suggested.

Highlights

At present, titanium (Ti) alloys are one of the principal materials in nuclear and marine engineering [1,2,3,4]. α- and near-α Ti alloys (Russian industrial names PT-3V, PT7M, etc.) are used most often in nuclear power engineering [3,4], new two-phase α + β alloys are increasingly used in marine engineering in recent years [1,2]
The diffraction peak positions on the X-ray diffraction (XRD) patterns are close to the theoretical values for α-Ti
All studied Ti alloy specimens obtained by spark plasma sintering (SPS) had high strength and good plasticity in tension testing at room temperature

Summary

Introduction

Titanium (Ti) alloys are one of the principal materials in nuclear and marine engineering [1,2,3,4]. α- and near-α Ti alloys (Russian industrial names PT-3V, PT7M, etc.) are used most often in nuclear power engineering [3,4], new two-phase α + β alloys are increasingly used in marine engineering in recent years [1,2]. The extreme operational conditions (high temperatures, loads, impact of corrosion-aggressive ambient, radiation environment, etc.) to which they are exposed impose high requirements of the mechanical properties and corrosion resistance of the Ti alloys. Hot salt corrosion (HSC) is one of the most dangerous kinds of destructive corrosion for Ti products utilized at elevated temperatures and in corrosion-aggressive media [5,6,7]. HSC develops intensively beneath the deposits of crystal halogenide salts (chlorides, bromides, iodides) in the presence of water (bound in the salt crystals, occluded in the salt crystals, or present in ambient air) on the Ti alloy surfaces. The character of HSC (general corrosion, pitting corrosion, or intergranular corrosion) depends on the operational conditions (atmospheric humidity, oxygen pressure, temperature, thickness and composition of the salt deposits) and on the structure and phase composition of the Ti alloys [5]. The case of the intergranular HSC, which may lead to formation of cracks and rapid destruction of the Ti alloys in the external stress conditions, is the most dangerous [5,8,9]

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