Structure and Properties of Ti-Al-Ta and Ti-Al-Cr Cladding Layers Fabricated on Titanium

Daria V Lazurenko,Ivan Yu Petrov,Andreas Stark,Ivan A Bataev,Mikhail G Golkovsky,Ilia S Laptev,Alexey A Ruktuev,Florian Pyczak

doi:10.3390/met11071139

Abstract

Being one of the most high-demand structural materials, titanium has several disadvantages, including low resistance to high-temperature oxidation and wear. The properties of titanium and its alloys can be improved by applying protective intermetallic coatings. In this study, 2 mm thick Ti-Al-Ta and Ti-Al-Cr layers were obtained on titanium workpieces by a non-vacuum electron-beam cladding. The microstructure and phase compositions of the samples were different for various alloying elements. The Cr-containing layer consisted of α2, γ, and B2 phases, while the Ta-containing layer additionally consisted of ω′ phase (P3¯m1). At the same atomic concentrations of aluminum and an alloying element in both layers, the volume fraction of the B2/ω phase in the Ti-41Al-7Ta alloy was significantly lower than in the Ti-41Al-7Cr alloy, and the amount of γ phase was higher. The Ti-41Al-7Cr layer had the highest wear resistance (2.1 times higher than that of titanium). The maximum oxidation resistance (8 times higher compared to titanium) was observed for the Ti-41Al-7Ta layer.

Highlights

Titanium and Ti-based alloys are widely used in aerospace engineering, shipbuilding, chemical engineering, and power engineering due to their outstanding properties, such as high strength, excellent corrosion resistance, and low density
The Cr-containing layer consisted of α2, γ, and B2 phases, while the Ta-containing layer consisted of ω phase (P3m1)
The structure of the cladding layers was thoroughly characterized using a combination of X-ray diffraction (XRD) and scanning electron microscopy (SEM) together with energy dispersive X-ray (EDX)

Summary

Introduction

Titanium and Ti-based alloys are widely used in aerospace engineering, shipbuilding, chemical engineering, and power engineering due to their outstanding properties, such as high strength, excellent corrosion resistance, and low density. Long exposure of titanium to air at a temperature above 700–800 ◦C results in forming an oxide scale that can be peeled off from the surface [1,2]. The oxygen absorbed by titanium is spent on the formation of a scale and dissolves in it [3,4]. These factors have a negative impact on the durability of parts being used at high temperatures. The low wear resistance of titanium is explained by its high tendency to adhesion during friction. Titanium can be used in various friction units (fasteners, threaded joints, radial thrust roller bearings, rotating shafts, etc.), its utilization is impossible without preliminary surface treatment

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Discussion

Conclusion