Plasma-nitrided α-β Ti alloy: layer characterization and mechanical properties modification

Evaluating the effects of plasma diffusion processing and duplex diffusion/PVD-coating on the fatigue performance of Ti–6Al–4V alloy

“…Again, considering a 'defect-free' condition before the test, fatigue crack initiation becomes the critical stage which dictates the fatigue life. Thus, surface treatments have the potential to play a key role in determining fatigue behaviour, particularly since the surface, where damage accumulates due to plastic strains several times larger than in the bulk [36], is the most likely origin of fatigue cracks. The improvement in fatigue life can be attributed to surface strengthening associated with the reduced mobility of dislocations and therefore the inhibition of slip step formation, together with the presence of a compressive residual stress state at the surface (due to lattice strain induced by interstitially-located nitrogen and/or oxygen).…”

AFM of titanium nitride layers prepared under glow discharge conditions

“…One of promising and widely studied method is nitriding under glow discharge. Several groups of researchers have investigated the parameters of nitrided layers produced by this method [1,14,[24][25][26][27][28][29][30]. In most cases common investigations performed by means of electron microscopy (SEM) and X-ray spectroscopy (XPS) are applied to get information concerning layer thickness, its structure in a microscopic scale as well as its phase and chemical composition.…”

Effect of Plasma Nitriding Environment and Time on Plain Fatigue and Fretting Fatigue Behavior of Ti–6Al–4V

“…In the case of the plasma-nitrided samples, the samples nitrided in nitrogen gas exhibited superior plain fatigue lives compared with the samples nitrided in the nitrogen-hydrogen mixture, possibly due to the relatively higher surface hardness of the samples nitrided in the nitrogen-hydrogen mixture environment, which probably reduced the toughness of the plasma-nitrided layer. Raveh et al [15] reported that the fracture toughness of samples nitrided in pure nitrogen gas was higher than that of the samples nitrided in a nitrogenhydrogen mixture (53 vs. 47 MPaHm). For samples nitrided in the nitrogen-hydrogen mixture, those nitrided for 18 h exhibited superior fatigue lives than those nitrided for 4 h. This trend was observed for samples nitrided in nitrogen gas at lower stress levels only, and the converse was true at higher stress levels of 550 and 700 MPa.…”

“…Raveh et al [15] showed an improvement in plain fatigue resistance by low-pressure radio-frequency (RF) plasma nitriding performed at 420-470°C. Samples nitrided in nitrogen exhibited a superior plain fatigue resistance compared to samples nitrided in a mixture of nitrogen, hydrogen, and argon.…”

“…One proposal for overcoming this problem is to perform the nitriding process at relatively lower temperatures (less than 600°C) [11,13]. To date, however, only a limited amount of work has been performed on low-temperature plasma-nitrided Ti-6Al-4V [14][15][16][17][18].…”