Surface hardening of Ti alloys by gas-phase nitridation: Kinetic control of the nitrogen surface activity

Increasing surface hardness of austenitic stainless steels by pack nitriding process

“…On the other hand, the tendency of precipitation of chromium nitrides may be suppressed if the nitriding process is conducted at low enough nitrogen pressures. Indeed, it has been reported that titanium alloys can be nitrided under a low nitrogen pressure of decomposition of Cr 2 N powder without causing the formation of titanium nitrides [16]. This finding may be of significance with relevance to nitriding of stainless steels as it is more difficult to suppress the formation of titanium nitrides than the formation of chromium nitrides, although the solubility of nitrogen is higher in titanium alloys than in stainless steels [17,18].…”

Characterization of Thermochemically Surface-Hardened Titanium by Light Optical Microscopy

“…The resulting surface layer of TiN has a golden color and will aesthetically change the appearance of the treated Ti, but will result in high hardness and low friction coefficient. More recently, attempts have been made to control the nitrogen-containing atmosphere to develop exclusively a nitrogen diffusion zone by applying a very low partial pressure of N2 to avoid formation of Ti-nitrides [7]. There is limited work in the literature on carburizing of titanium [8,9,10,11,12].…”

Micro-Alloying and Surface Texturing of Ti-6Al-4V Alloy by Embedding Nanoparticles Using Gas Tungsten Arc Welding

“…The micro-hardness of the treated surface layer decreased with the increasing size of the nanoparticles, while the roughness of the surface increased with the increasing welding current. The heat input into the surface during the surface melting process resulted in the formation of various intermetallic compounds capable of further increasing the hardness of the Ti-6Al-4V surface.include carburizing using laser surface processing [8] Physical and Chemical vapour deposition [9], thermal oxidation [10][11][12], diffusion related process [13], surface melting and alloying [14]. Among the various available techniques, surface melting and microalloying have the potential to harden the surfaces of Ti-alloys without causing significant changes to other mechanical properties within the material.…”

“…Selah et al demonstrated that carburising of the Ti surface using continuous-wave CO 2 laser with a maximum power of 3 kW led to the formation of TiC crystals, which increased the hardness of the alloy surface from 350 HV 0.2kg for the untreated samples to a maximum of 800 HV 0.2kg , While this technique has the capability to improve the mechanical properties of the Ti surface, the equipment used in the process is prohibitively expensive. Liu et al [13] demonstrated that gas-phase nitriding under kinetic control of the nitrogen activity resulted in a doubling of the surface hardness of the Ti sample. Among the available techniques for improving the hardness of the Ti-6Al-4V alloy is surface melting and alloying using gas tungsten arc welding (GTAW).…”