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Modification of the Microstructure and Properties of Laminate Titanium Alloy - TiAl Intermetallic Phases Composites By A Duplex Surface Engineering Treatment

Modification of the Microstructure and Properties of Laminate Titanium Alloy - TiAl Intermetallic Phases Composites By A Duplex Surface Engineering Treatment

Laminate TiAl3 - titanium alloy composites have unique mechanical properties which result from a combination of the properties of the Ti-Al type intermetallic phases, such as the high stiffness and low density, and the properties of the titanium alloy, primarily its high ductility. These composite materials have already been used in industry, but their application is limited by the low resistance to frictional wear and to oxidation at elevated temperatures. The process of diffusion bonding of titanium alloys with an aluminum foil, followed by magnetron sputtering combined with glow discharge-assisted oxidizing, yields a gradient-type material, i.e. a laminate composite built of the TiAl3-reinforced titanium alloy with a diffusion surface layer of the Al2O3+Ti-Al intermetallic phase type.

The paper presents the results of examination of the structure (by optical, SEM and TEM microscopy), phase composition, chemical composition, frictional wear resistance of the Al2O3+TixAly intermetallic composite surface layers produced on the composites, described above, by a duplex method that combines magnetron sputtering and plasma oxidizing processes. The composite surface layers have a diffusion character, and their microstructure, thickness and phase composition can be modified by modifying the parameters of the hybrid process, in particular the parameters of the glow discharge oxidizing, since these decide about whether the structure of the layer is nano-crystalline or fine-grained and thereby about the properties of the laminate composite.

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Titanium nitride coatings synthesized by IPD method with eliminated current oscillations

Abstract

This paper presents the effects of elimination of current oscillations within the coaxial plasma accelerator during IPD deposition process on the morphology, phase structure and properties of synthesized TiN coatings. Current observations of waveforms have been made by use of an oscilloscope. As a test material for experiments, titanium nitride TiN coatings synthesized on silicon and high-speed steel substrates were used. The coatings morphology, phase composition and wear resistance properties were determined. The character of current waveforms in the plasma accelerator electric circuit plays a crucial role during the coatings synthesis process. Elimination of the current oscillations leads to obtaining an ultrafine grained structure of titanium nitride coatings and to disappearance of the tendency to structure columnarization. The coatings obtained during processes of a non-oscillating character are distinguished by better wear-resistance properties.

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