Microstructure and mechanical properties of surface treated cast titanium with Nd:YAG laser

Abstract

Objective: To investigate the effect of laser surface treatment of cast titanium alloy on microstructure and mechanical properties.Methods: Dumbbell-and plate-shaped cast titanium specimens were prepared for mechanical testing and microstructure analysis. After the cast surfaces of each specimen were laser-treated using a dental Nd:YAG laser machine at 240 V and 300 V with and without argon gas shielding, tensile testing and microstructure analysis were conducted.Hardness depth profiles were also made from the cross-section of laser-treated cast specimens. Microstructural and chemical analysis were performed by means of the SEM, XRD, AES and WDS.Results: The results of tensile testing and Vickers hardness depth profiling showed that laser treatment improved the mechanical properties. Bulk microstructure of as-cast titanium was mainly composed of α-grains with acicular and widmanstatten patterns.The laser melted zone was characterized by columnar beta grains. When the emission voltage of laser increased to 300 V, a larger grain size was promoted. The XRD analysis indicated that the beta phase formation was clearly noticeable after laser surface treatment. Supplementary marked peaks of the TiO, TiO 2 and Ti 2 N were detected without argon gas shielding. When argon shielding gas was used, the presence of titanium oxide was significantly reduced and the peaks of titanium nitride disappeared.Significance: Laser treatment on cast titanium surfaces showed significant enhancement of mechanical properties and modification of microstructures, and therefore could produce reliable titanium metal frameworks for dental prostheses.3

Influence of Rapid Solidification on the Thermophysical and Fatigue Properties of Laser Additive Manufactured Ti-6Al-4V Alloy

“…Consequently, improvements in machinery performance and safety in aerospace, automotive, can be realized by the method [21]. According to Poulon-Quintin et al [22], laser beams, because of specific thermal characteristics induced by laser irradiation, can generate specific microstructures including metastable phases and nano-crystalline grains. Laser processing offers unique and significant quality and cost advantages over traditional techniques.…”

Tensile and Flexural Strength of Commercially Pure Titanium Submitted to Laser and Tungsten Inert Gas Welds

“…Some studies have reported that welded structures present worse properties than cast specimens, such as lower mechanical resistance, higher corrosion and increased pore incorporation (11,22). Using scanning electron microscopy, it was observed that the laser-welding region is not completely melted and the 0.7 mm penetration depth reduced specimen's resistance, indicating that this method is not suitable for welding surfaces exceeding 1 mm in diameter (22).…”

“…The laser process is the most common method used to weld titanium. It is characterized by a monochrome electromagnetic light whose energy beam can be concentrated in a focal point resulting in the union process (11). Some advantages of this method are the absence of direct contact with the welded area, more defined welding area with less heating and no influence of magnetic field on the laser beam (13,14).…”

“…Thus, the processes that seem to be suitable to weld titanium are plasma, electron beam, laser, hearth brazing, infrared brazing, metal inert gas (MIG) and tungsten inert gas (TIG) (3,10). It is important to note that all these methods are performed in a protective atmosphere (11,12), because the contamination with gases turns the metal crumbly and it can result in alterations of the crystalline structure, that influence directly on the mechanical properties of the titanium and its alloys. The laser process is the most common method used to weld titanium.…”

Laser Surface Modification — A Focus on the Wear Degradation of Titanium Alloy

“…With this, vaporization is avoided due to rapid heating and solidification of the molten clad, which helps to inhibit long-range diffusion, avoid crystallization, achieve strong metallurgical bond with the substrate, and increase hardness [6,34]. Laser beam-specific thermal characteristics induced by laser irradiation help generate specific microstructures, including metastable phases and nano-crystalline grains, which is an advantage over conventional techniques [35]. The most important factor to consider during cladding process is the melting of the alloying material to the substrate.…”