Laser Surface Nitriding of Ti–6Al–4V Alloy in Nitrogen–Argon Atmospheres

Abstract

Surface-nitrided layers of Ti–6Al–4V alloy were fabricated using a diode laser in pure and mixed gas atmospheres of nitrogen and argon. The surface morphology, microstructure, hardness, and cracks of the nitrided layers were investigated. In all gas atmospheres, the layers showed smooth and humped regions, and consisted of planar nitrogen titanium (TiN), dendrites, and acicular martensite. The surface roughness was improved dramatically as the nitrogen concentration of the atmosphere was diluted with argon. Overall, the hardness of the nitrided layer was greatest for pure nitrogen and it tended to decrease as the concentration of argon in the atmosphere increased. However, the hardness of the layer for pure nitrogen also decreased rapidly, from the surface to matrix, in comparison to the diluted nitrogen atmospheres. It was shown that the number and size of dendrites, which determine hardness, are controlled by the nitrogen concentration. The dendrites of the nitrided layer were denser and smaller in a pure nitrogen atmosphere, than in diluted nitrogen atmospheres. Longitudinal and transverse cracks were observed in the nitrided layers. These two types of cracks were decreased or even eliminated as the argon concentration of the nitrogen–argon atmosphere was increased. Therefore, by diluting the nitrogen atmosphere with argon, the nitrided layer properties, in terms of surface roughness and cracks, can be improved, but this may also cause a reduction in the layer hardness.

Surface engineering and the application of laser-based processes to stents - A review of the latest development

“…Li et al [ 151 ] fabricated nitridated surface on Ti–6Al–4V alloy surface through diode LGN. They used a mixture of nitrogen and argon and found the higher fraction of nitrogen resulted in the higher surface hardness but also produced a nitridated layer with both longitude and transversal cracks.…”

“…Reduced nickel ion releasing, increased corrosion and wear resistance was also found on the Nd-YAG LGN NiTi surface [ 154 ]. Additionally, increased biocompatibility [ 155 ], especially increased endothelialisation [ 151 ] were also found on surface of stent-related materials after LGN. The positive function of LGN on stents and stent-related materials is obviously proved.…”

The Laser Alloying Process of Ductile Cast Iron Surface with Titanium Powder in Nitrogen Atmosphere

“…Titanium, besides high affinity to carbon, also has a high affinity to nitrogen and can form titanium nitrides and carbonitrides, which, like carbides, exhibit high hardness and can reinforce the composite structure for high wear resistance [25,26]. Many studies on titanium surface nitriding have been conducted, and the results are available in the literature [27,28], while only a few studies have been conducted on ductile cast iron surface alloying with titanium and nitrogen [29]. In the available research in this field [29], Si 3 N 4 was used as the source of nitrogen in the alloying process, and no titanium carbonitrides were found in the produced surface layers.…”

A Review on Friction Reduction by Laser Textured Surfaces in Internal Combustion Engines

“…In the field of materials science, lasers can be used e.g., for metal ablation [16], to create custom tailored metal alloys, insitu alloying of metals [16], or nitridation [17,18]. Liu et al created Ni60/Nickel-coated graphite/TiB 2 composite coatings for self-lubricating dry contacts [19] through laser ablation.…”