Effect of nitriding conditions of Ti6Al7Nb on microstructure of TiN surface layer

(Ti,Al)O2 Whiskers Grown during Glow Discharge Nitriding of Ti-6Al-7Nb Alloy

“…It is characteristic for the PN process that the nodules are the coarser, the higher the nitriding temperature, while the bright spots representing point surface defects remain practically the same. The cross-section scanning and transmission electron microscopy (SEM/TEM) investigations not only confirmed the presence of a surface undulation representing the nodular features, but also proved that they increase with the PN temperature both for the Ti-6Al-4V [ 8 ] and Ti-6Al-7Nb [ 2 , 9 ] alloys. However, none of the images published so far gave any indication of the nature of the point-like objects observed with the SEM method.…”

“…Next, the samples were heated with a resistive table up to 620 • C. Afterwards, the glow discharge process was started and maintained for 6 h. Finally, the flow of nitrogen was cut off to stop discharge, the resistive heating was switched off, and the system was cooled down with a chamber. The scheme presenting the sample placing in the chamber is described elsewhere [2].…”

“…A glow discharge plasma nitriding (PN) of parts made of Ti-6Al-4V and Ti-6Al-7Nb alloys is gaining an upper hand over gas nitriding (GN), as it allows the increase of surface hardness without compromising a high strength of the core material [ 1 ]. This is because the former process could be performed at much lower temperatures than the latter one, i.e., the PN secures formation of a continuous and slightly porous TiN surface layer even after processing duration of eight hours carried out at 600–850 °C [ 2 ], while achieving the comparable results with the GN of the same duration must be performed at 800–1050 °C [ 3 ]. A problem in the case of PN treatment is that it causes a surface roughening, increasing with the treatment temperature [ 4 , 5 ].…”

Improving the wear resistance of heavy-duty elements in tribomechanical systems by a combined laser-thermochemical processing method

“…For steels, the greatest strength, hardness, and wear resistance are achieved by nitriding. The review of studies [19][20][21][22][23][24][25][26][27][28] shows the high efficiency of the combined technology of nitriding+laser processing. This avoids the disadvantages of "classic" nitriding, hardens the material under a nitrided layer, and increases the diffusion layer's thickness.…”

“…However, the increase in nitrogen content in powders leads to a high porosity coating that is not suitable for our conditions. Laser treatment with melting after nitriding in the plasma medium [26] indicates the possibility of obtaining a strengthening effect by refining the microstructure by ultra-rapid cooling of the melt [27]. The thickness of the modified layer reaches 250 μm, which is an acceptable value.…”