Effect of Laser Gas Nitriding on the Microstructure and Corrosion Properties of Ti-6Al-4V Alloy
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概要
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Laser surface melting of Ti–6Al–4V alloy under a pure nitrogen environment of 30 L/min gas flow rate, was carried out with 200–600 mJ laser beams, produced by a Nd-YAG pulsed laser at 5 mm defocused distance, and 0.5–3 mm/s sample traverse velocities. The microstructure, hardness and corrosion behaviour of the nitrided samples were examined, using scanning electron microscopy, X-ray diffractometry (XRD), microhardness measurements across the workpiece cross-section and anodic polarization tests in 2 M HCl solution.The microstructures consisted mainly of a thin continuous layer of titanium nitride followed by nearly perpendicular dendrites, and below this, a mixture of small dendrites and large needles, which had a random orientation. The denderitic structure was the TiN phase, and the needle phase and the phase of the matrix between the dendrites were nitrogen-enriched α′-Ti. The density of TiN dendrites decreased gradually towards the interface between the nitrided layer and the substrate. The melted zone showed a range of hardness of between 400–1300 Hv, the hardness being found to be related to the dendrite populations. An improvement in corrosion behaviour, associated with the presence of a good TiN coating, was observed. Also, the improved pitting corrosion resistance is obtained due to the microstructural changes after laser treatment.
- 社団法人 日本鉄鋼協会の論文
- 2007-05-15
著者
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Monirvaghefi Mahmood
Materials Engineering Department Isfahan University Of Technology
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Salehi Mehdi
Materials Engineering Department Isfahan University Of Technology
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RAZAVI Reza
Materials Engineering Department, Isfahan University of Technology
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MOZAFARINIA Reza
Materials Engineering Department, Malek Ashtar University of Technology
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Razavi Reza
Materials Engineering Department Isfahan University Of Technology
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Mozafarinia Reza
Materials Engineering Department Malek Ashtar University Of Technology