Investigation of surface properties of high temperature nitrided titanium alloys (original) (raw)
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The Effect of Low Temperature Plasma Nitriding on Wear Resistance of Ti6Al4V Alloy
Acta Physica Polonica A, 2014
The eect of low temperature plasma nitriding on wear resistance of Ti6Al4V alloy were investigated. There have been several studies to investigate the low temperature plasma nitriding on Ti6Al4V alloy. Plasma nitriding processes under gas mixture of N2/H2 = 3 were performed at temperature 535 • C for duration of 4, 8 and 12 h. Adhesive wear tests were carried out by using a tribometer in block-on-ring conguration (ASTM G77), in sliding conditions, without lubricants and in air. Surface hardness of the plasma nitrided samples were measured by a Vickers hardness tester machine. Scanning electron microscopy studies were conducted to understand the wear mechanisms involved during the adhesive wear. Wear rate was calculated using weight loss per unit sliding distance. It was found that the wear resistance and surface hardness of the alloy improved considerably after plasma nitriding process. The wear resistance of the plasma nitrided samples were higher than of the unnitrided samples. Extension of nitriding times from 4 h to 12 h in the Ti6Al4V alloy improved remerkably the wear resistance and surface hardness.
Treatment of Surface Properties of Titanium with Plasma (Ion) Nitriding
Defect and Diffusion Forum, 2009
In order to improve the poor surface hardness and the wear resistance, titanium has been nitrided with plasma (ion) nitriding which is one of the methods to treat surface properties of titanium alloys. The increment at surface hardness and so the wear resistance of nitrided titanium alloys has been provided by means of compound layer (ε-Ti 2 N+δ-TiN) and diffusion zone (α-Ti) occurred by plasma ion nitriding. The goal of the present paper is to investigate effects of nitriding temperature and nitriding time on the microstructure and hardness value of nitrided surface layers. A systematic study was undertaken with specimens of commercial pure Ti and Ti-6Al-4V alloy. As treatment parameters, we have used; nitriding time (from 2 to 9 hour), nitriding atmosphere (H 2 -80%N 2 ), total pressure (1 kPa) and cathode temperature (from 600 to 800 o C). The Vickers indenter was used for analysis of the micro hardness measurements. The thin hardened layer at the nitrided surface was characterized by glancing-angle X-ray difractometer. X-ray diffraction analysis has confirmed the formation of ε-Ti 2 N and δ-TiN phases on the nitrided specimens. Experimental details and characterization of plasma (ion) nitrided titanium have reported and discussed.
Plasma nitriding behavior of Ti6Al4V orthopedic alloy
Surface and Coatings Technology, 2008
The influence of plasma nitriding on mechanical, corrosion and tribological properties of Ti6Al4V has been investigated using X-ray diffraction, microhardness tester, scanning electron microscopy, pin-on-disc tribotester, electrochemical polarization and impedance spectroscopy. Plasma nitriding treatment of Ti6Al4V has been performed in 25%Ar-75%N 2 gas mixture, for treatment times of 1-4 h at the temperatures of 650-750°C. The corrosion tests were carried out in Ringer solution at 37°C, and the wear tests were performed in dry sliding conditions. XRD analyses confirm the formation of δ-TiN and tetragonal ɛ-Ti 2 N phases in the modified layer. It was observed that the surface hardness and wear resistance increase as the treatment time and temperature increase. The electrochemical impedance measurements indicate a decrease in double layer capacitance value and increase in charge transfer resistance for the nitrided specimens compared to the untreated ones.
Nano- and micro-tribological behaviours of plasma nitrided Ti6Al4V alloys
Journal of the Mechanical Behavior of Biomedical Materials, 2017
Plasma nitriding of the Ti-6Al-4V alloy (TA) sample was carried out in a plasma reactor with a hot wall vacuum chamber. For ease of comparison these plasma nitrided samples were termed as TAPN. The TA and TAPN samples were characterized by XRD, Optical microscopy, FESEM, TEM, EDX, AFM, nanoindentation, micro scratch, nanotribology, sliding wear resistance evaluation and in vitro cytotoxicity evaluation techniques. The experimental results confirmed that the nanohardness, Young's modulus, micro scratch wear resistance, nanowear resistance, sliding wear resistance of the TAPN samples were much better than those of the TA samples. Further, when the data are normalized with respect to those of the TA alloy, the TAPN sample showed cell viability about 11% higher than that of the TA alloy used in the present work. This happened due to the formation of a surface hardened embedded nitrided metallic alloy layer zone (ENMALZ) having a finer microstructure characterized by presence of hard ceramic Ti 2 N, TiN etc. phases in the TAPN samples, which could find enhanced application as a bioimplant material.
Mechanisms of r.f. plasma nitriding of Ti-6Al-4V alloy
1993
The objective of the current study was the gradual development of the formation of the nitride layer during inductive r.f. plasma nitriding. The study centers on characterization of refined layers and plasma diagnostics in the vicinity of the sample, and raises critical questions of how the layers and interracial microstructure might affect the near-surface properties. The composition of the plasma near the surface of the sample (plasma layer) was examined by optical emission spectroscopy and mass spectrometry during plasma nitriding and while sputtering the sample after the nitriding process. It was observed that during the nitriding process, the plasma layer contains Ti, NH,, species, N (or/and N + ), H,, species (or/ and H +2). However, when the nitrided sample was exposed to argon plasma, Ti, A1 and NH were observed. It was found that two distinct sublayers, comprising d-TiN and &TiN + e-Ti~N phases, were formed with alloying elements in a segregated zone, followed by a solid solution of nitrogen in titanium. The formation of the uppermost sublayer (&TIN phase), containing H, NH, and N, in addition to Ti depleted of AI and V, has a strong effect on the diffusion of nitrogen into a-Ti and on the layer properties. This can be enhanced if hydrogen is present in the nitriding atmosphere and is prevented if hydrogen is replaced by argon. Therefore, the nitrogen content in the layer results in the formation of nitride phases and is accompanied by an improvement in mechanical properties.
Several plasma diffusion processes for improving wear properties of Ti6Al4V alloy
Wear, 2009
Different kinds of diffusion processes, plasma nitriding, oxidizing and oxynitriding as of a combination of other two, have been applied to Ti6Al4V alloy to evaluate the effect of treatment times (1 and 4 h) and temperatures (650 and 750 • C) on wear properties of the alloy. It was observed that a hard modified layer was produced on the surface of the alloy after each diffusion process. While TiN and Ti 2 N phases form in the modified layer with plasma nitriding, mainly TiO 2 phase forms after plasma oxidizing treatment. The wear tests performed at different normal loads showed that all treated samples, except for nitrided and oxidized at 650 • C for 1 h, exhibited higher wear resistance than untreated Ti6Al4V alloy. The plasma nitrided samples showed adhesive wear. On the other hand, while the plasma oxidizing samples displayed adhesive wear at lower loads, wear mechanism changed to abrasive wear as the load increased because the oxide film which covers the surface was broken during the sliding at higher loads.
Mechanism of r.f. plasma nitriding of Ti-6A1-4V alloy
The objective of the current study was the gradual development of the formation of the nitride layer during inductive r.f. plasma nitriding. The study centers on characterization of refined layers and plasma diagnostics in the vicinity of the sample, and raises critical questions of how the layers and interracial microstructure might affect the near-surface properties. The composition of the plasma near the surface of the sample (plasma layer) was examined by optical emission spectroscopy and mass spectrometry during plasma nitriding and while sputtering the sample after the nitriding process. It was observed that during the nitriding process, the plasma layer contains Ti, NH,, species, N (or/and N +), H,, species (or/ and H +2). However, when the nitrided sample was exposed to argon plasma, Ti, A1 and NH were observed. It was found that two distinct sublayers, comprising d-TiN and &TiN + e-Ti~N phases, were formed with alloying elements in a segregated zone, followed by a solid solution of nitrogen in titanium. The formation of the uppermost sublayer (&TIN phase), containing H, NH, and N, in addition to Ti depleted of AI and V, has a strong effect on the diffusion of nitrogen into a-Ti and on the layer properties. This can be enhanced if hydrogen is present in the nitriding atmosphere and is prevented if hydrogen is replaced by argon. Therefore, the nitrogen content in the layer results in the formation of nitride phases and is accompanied by an improvement in mechanical properties.
R.F. plasma nitriding of Ti6A14V alloy
Thin Solid Films, 1990
Titanium alloy (Ti-6AI-4V) samples were nitrided in low pressure (7 mbar) inductive r.f. (0.5 MHz) plasmas of nitrogen or nitrogen-hydrogen. The nitriding time was 5 h and the temperatures of the samples during the nitriding process were 470 + 20°C and 420 + 20°C in the discharge and afterglow regions respectively. The effect of the sample location in the reactor and of the N2:H 2 ratio in the gas mixture was studied. In the centre of the discharge region e-Ti2N plus 5-TIN phases were formed on top of a solid solution of nitrogen in titanium, Qt-(Ti, N). In the afterglow region an 0t-(Ti, N) plus c-Ti2N structure was obtained.
Tribocorrosion behaviour of plasma nitrided and plasma nitrided+oxidised Ti6Al4V alloy
Surface and Coatings Technology, 2006
This paper reports the influence of low pressure plasma nitriding treatments, some of them followed by plasma assisted oxidation on the mechanical properties and tribocorrosion resistance of a Ti6Al4V alloy. Nitridation was performed for 640 or 720 min at 600 and 700°C in a r.f. plasma equipment, using a N 2 -H 2 gas mixture at 7.5 Pa. Some of the samples were then post-oxidized at 700°C for 15 and 60 min, within a O 2 plasma of 9.5 Pa. XRD results revealed the occurrence of the Ti 2 N phase for the nitrided samples. The oxidized surface layers are poorly crystallised with rutile and traces of anatase TiO 2 nanocrystallites. Microhardness tests showed a significant improvement of the surface hardness whatever the treatment, with a slight effect of the treatment temperature. The tribocorrosion results clearly showed that plasma treatments have a strong influence on the tribocorrosion behaviour of the material. Both the corrosion and wear performance of the samples are improved by the increase of the processing temperature.
Journal of Materials Processing Technology, 2018
A thick layer of Ni X Ti Y (NiTi and NiTi 2) was deposited on Ti-6Al-4V alloy by tungsten inert gas (TIG) cladding process using Ni and Ti powder mixture prepared by ball milling route as precursor. The analysis shows that the microstructure of the produced NiTi coating principally governs by the heat input, which was controlled through the employed processing current. The hardness of the NiTi clad layer measured by Vickers micro-indentation method was found reasonably higher as compared to Ti-6Al-4V alloy substrate. The XRD and EDS analysis of the clad layer revealed the formation of NiTi and NiTi 2 as major phases along with some unreacted Ti and TiAl 3 intermetallic. The sliding abrasive wear of the coating performed against abrasive disc shows upto 9.5 times reduction in the wear value as compared to the uncoated Ti-6Al-4V alloy as measured by its height loss. The experimental results revealed an ample effect of the TIG current on the hardness value and wear characteristic of the clad layer, which is predominantly dependent on the morphology and percentage of phase constituent formed. The produced NiTi coating has prospective applications in biomedical, where inadequate wear resistance of Ti-6Al-4V alloy is the major concern for its use.