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Surface engineering and chemical characterization in ion nitrided titanium and titanium alloys

TL;DR: In this paper, the chemical and physical characteristics of ion-nitrided surface layers, obtained on α-β titanium alloys, are examined and correlated both with the working conditions adopted in the ionnitriding process and with the alloy chemical composition.
Abstract: The chemical and physical characteristics of ion-nitrided surface layers, obtained on α-β titanium alloys, are examined and correlated both with the working conditions adopted in the ion-nitriding process and with the alloy chemical composition. Besides the influence of the working parameters on the morphology and on the microstructures of the ion-nitrided surface layers, mainly the alloy element distributions both in surface coatings and in the substrate are analysed for five α-β titanium alloys of industrial use, and for titanium c,p. as reference, ionnitrided at various treatment temperatures. The nitriding process forms, on titanium alloy parts, high-hardness surface layers consisting of TiN (δ phase) and Ti2N (ɛ phase) nitrides and an interstitial solid solution of nitrogen in the close-packed hexagonal lattice of titanium (α phase). The presence and the extent of these phases as well as the ion-nitrided layer morphology are essentially determined by the alloy chemical composition and the working parameters. In particular a low-temperature treatment produces an extended nitrogen diffusion in the matrix beneath a thin continuous nitrided layer, while a high-temperature treatment produces prevalently a continuous nitrided surface layer. The alloy element distribution appears differentiated in the various phases and may be correlated with the different affinity of these elements with nitrogen.
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Journal ArticleDOI
TL;DR: In this paper, the tribocorrosion behavior of a TiN-Ti 2 N alloy was investigated in a 0.9 M NaCl solution at room temperature by means of a sliding wear tribometer, utilizing alumina balls as the counterface material.
Abstract: The tribocorrosion behavior of plasma nitrided Ti–6Al–4V alloy is investigated in a 0.9 M NaCl solution at room temperature by means of a sliding wear tribometer, utilizing alumina balls as the counterface material. Tests were performed at open circuit potential and under anodic polarization and the electrochemical parameters, namely anodic current, potential and galvanic current were continuously monitored. The plasma nitriding treatments were performed at two different temperatures, 973 K and 1173 K, and the resulting microstructures and phases were characterized. At 973 K a thin TiN–Ti 2 N layer was formed while at the higher temperature this compound layer was thicker and an inner hardened sublayer was present. In the absence of such an inner layer the sliding of the alumina pins promoted the nucleation and growth of microcracks in the nitride layer, leading to quick failure of the coating. The samples treated at higher temperature showed a more uniform wear process of the nitride layer, without crack formation, and even after its removal, the hardened sublayer did not suffer from the typical delamination wear of untreated Ti–6Al–4V. The damaging or removal of the protective passive film due to rubbing leads to the formation of a galvanic couple between the anodic wear track and the outside surface. The fraction of electrochemically removed material with respect to the total wear volume was approximately 0.2 for the untreated alloy and 0.5 for the nitride layer.

122 citations

Journal ArticleDOI
TL;DR: AISI 316L stainless steel (SS) and titanium nitriding were studied in a low pressure arc-assisted Nitriding process where the substrate temperature and the plasma parameters are uncoupled as mentioned in this paper.
Abstract: AISI 316L stainless steel (SS) and titanium nitriding were studied in a low pressure arc-assisted nitriding process where the substrate temperature and the plasma parameters are uncoupled. Lower nitriding temperature limits were explored for constant plasma parameters in Ar–N2 gas mixtures and substrates at floating potential. Nitrogen superficial concentration, layer thicknesses and X-ray diffraction analyses were performed on SS specimens nitrided at two temperatures (580 and 680 K) for different times and titanium nitriding was studied in the temperature range 750–1025 K. At low temperature, the nitriding performances are limited by a plasma–surface phenomenon that probably involves recombination of nitrogen atoms.

75 citations

Journal ArticleDOI
01 Mar 1997-Wear
TL;DR: In this paper, dry sliding tests were carried out under different load and sliding speed conditions on Ti6Al-4V alloy plasma nitrided at three temperatures 973, 1073, and 1173 K.

71 citations

Journal ArticleDOI
01 Apr 2013-Wear
TL;DR: A modified plasma nitriding treatment developed for Ti-6Al-4V alloy at a low temperature (600 Ã 0 ) and in a dilute N2 atmosphere (3% N2) has shown to improve the alloy tribological properties and resistance to surface crack initiation and propagation as mentioned in this paper.

50 citations

Journal ArticleDOI
TL;DR: In this article, the corrosion properties of TiN layers obtained by glow discharge on Ti-6Al-4V samples were investigated by polarisation curves, cyclic voltammetry and loss weight tests, in different HCl solutions.

47 citations

References
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Book
01 Jan 1987

848 citations

Journal ArticleDOI
TL;DR: The possibilities for surface hardening of titanium alloys by alloying with nitrogen are reviewed in this paper, where both solid state and liquid state alloying has been carried out in the solid state by plasma nitriding and in the liquid state by laser melting in nitrogen.
Abstract: The possibilities for surface hardening of titanium alloys by alloying with nitrogen are reviewed. Alloying has been carried out in the solid state by plasma nitriding and in the liquid state by laser melting in nitrogen. Microstructure, hardness profiles, and fatigue and wear properties have been examined. Wear resistance was found to be greatly improved by both techniques, although at the expense of a drop in fatigue properties. Case depths of 0.1 mm were produced by plasma nitriding, while 0.5 mm case depths and a maximum hardness of 1400 HV0.1 were achieved by laser alloying.

197 citations

Journal ArticleDOI
TL;DR: In this paper, the tribocorrosion behavior of a TiN-Ti 2 N alloy was investigated in a 0.9 M NaCl solution at room temperature by means of a sliding wear tribometer, utilizing alumina balls as the counterface material.
Abstract: The tribocorrosion behavior of plasma nitrided Ti–6Al–4V alloy is investigated in a 0.9 M NaCl solution at room temperature by means of a sliding wear tribometer, utilizing alumina balls as the counterface material. Tests were performed at open circuit potential and under anodic polarization and the electrochemical parameters, namely anodic current, potential and galvanic current were continuously monitored. The plasma nitriding treatments were performed at two different temperatures, 973 K and 1173 K, and the resulting microstructures and phases were characterized. At 973 K a thin TiN–Ti 2 N layer was formed while at the higher temperature this compound layer was thicker and an inner hardened sublayer was present. In the absence of such an inner layer the sliding of the alumina pins promoted the nucleation and growth of microcracks in the nitride layer, leading to quick failure of the coating. The samples treated at higher temperature showed a more uniform wear process of the nitride layer, without crack formation, and even after its removal, the hardened sublayer did not suffer from the typical delamination wear of untreated Ti–6Al–4V. The damaging or removal of the protective passive film due to rubbing leads to the formation of a galvanic couple between the anodic wear track and the outside surface. The fraction of electrochemically removed material with respect to the total wear volume was approximately 0.2 for the untreated alloy and 0.5 for the nitride layer.

122 citations

Journal ArticleDOI

121 citations

Journal ArticleDOI
TL;DR: AISI 316L stainless steel (SS) and titanium nitriding were studied in a low pressure arc-assisted Nitriding process where the substrate temperature and the plasma parameters are uncoupled as mentioned in this paper.
Abstract: AISI 316L stainless steel (SS) and titanium nitriding were studied in a low pressure arc-assisted nitriding process where the substrate temperature and the plasma parameters are uncoupled. Lower nitriding temperature limits were explored for constant plasma parameters in Ar–N2 gas mixtures and substrates at floating potential. Nitrogen superficial concentration, layer thicknesses and X-ray diffraction analyses were performed on SS specimens nitrided at two temperatures (580 and 680 K) for different times and titanium nitriding was studied in the temperature range 750–1025 K. At low temperature, the nitriding performances are limited by a plasma–surface phenomenon that probably involves recombination of nitrogen atoms.

75 citations