Titanium boride coating by high power diode laser alloying of amorphous boron with titanium and its surface property investigations

Monisha, K and Shariff, SM and Sekar, A and Raju, R and Manonmani, J and Senthilselvan, J (2024) Titanium boride coating by high power diode laser alloying of amorphous boron with titanium and its surface property investigations. In: Optics and Laser Technology, 170 .

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Abstract

Present work deals with fabrication of superhard titanium boride coating on titanium surface with preplaced amorphous boron layer using high power diode laser alloying. Amorphous boron instantaneously converts into crystalline boron by the effect of high-power laser interaction, which rapidly drives the boron species into titanium liquid pool and form titanium boride precipitates by its convective flow. Negative Gibbs free energy (ΔG) and enthalpy (ΔH) of amorphous boron crystallization reaction introduces the concept of laser induced self-propagation synthesis. Gibbs free energy (ΔG) for the chemical reactions between Ti and B was calculated to confirm the spontaneous formation of titanium boride compound phases. The diffusion coefficient and activation energy were estimated to understand the phase formation and microstructural evolution. The structural phase, microstructure, microhardness and wear resistance of the laser borided titanium was investigated by XRD, optical and scanning electron microscopy, EDAX, Vickers microhardness analysis and linear reciprocating wear testing. The laser alloyed coating across the cross section shows formation of dendrites and whisker like microstructures. Average microhardness of 800–1600 HV0.2 was measured at different cross-sectional depths and an extreme hardness of about 3800–4700 HV0.2 was obtained in some regions of boron precipitates. The results showed a high negative value of Gibbs free energy of about −250 kJ/mol and −170 kJ/mol at ∼2000 °C respectively which confirms the spontaneity of TiB2 and TiB phase formation. The activation energy of the titanium boride is estimated to be 140 kJ/mol. The laser borided coating with the formation of TiB and TiB2 phases could be useful for surface engineering applications.

Item Type:	Journal Article
Publication:	Optics and Laser Technology
Publisher:	Elsevier Ltd
Additional Information:	The copyright for this article belongs to Elsevier Ltd.
Keywords:	Activation energy; Alloying; Borides; Boriding; Coatings; Free energy; Gibbs free energy; Microhardness; Scanning electron microscopy; Semiconductor lasers; Titanium compounds; Wear of materials; Wear resistance, Amorphous boron; Boron-layers; Diode-laser; High power; Laser alloying; Phase formations; Superhard; Titania; Titania surfaces; Titanium boride, Microstructure
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy)
Date Deposited:	28 Feb 2024 11:18
Last Modified:	28 Feb 2024 11:18
URI:	https://eprints.iisc.ac.in/id/eprint/83604

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