Several plasma diffusion processes for improving wear properties of Ti6Al4V alloy (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.
Wear, 2008
Titanium alloys, due to their excellent combination of low density, high strength to weight ratio, high corrosion resistance and biocompatibility, are widely used in the aerospace, automotive, chemical and biomedical industries. However, a main limit to the use of Ti alloys is their poor tribological behaviour. For this reason, different surface treatments and coatings have been developed for improving surface properties of Ti alloys. Among the most recent surface modification techniques, plasma electrolytic oxidation (PEO) has been successfully applied to titanium alloys. The aim of the present study was to investigate the friction and wear behaviour of a PEO coating on the Ti6Al4V alloy. The tribological behaviour of the PEO treated Ti alloy was compared with that of thin PVD coatings, such as TiN, (Ti,Al)N and CrN/NbN superlattice deposited on the same substrate. The tests were carried out under dry sliding conditions (slider-on-cylinder geometry) against a plasma-spray Al 2 O 3 -TiO 2 coated steel. TiN gave the best tribological performance among the PVD coatings, up to 20 N. The PEO treatment significantly reduced both wear and friction of the Ti6Al4V alloy, even under higher applied loads, up to 35 N.
Vacuum, 2003
Fretting wear behaviour of Ti-6Al-4V specimens after different diffusion processes is being analysed in the work. During the treatments (3 or 6 h annealing at the temperature 1023 K) the surface of the specimens has been exposed to a glow discharge plasma in the atmosphere composed of Ar and O 2 with two different oxygen concentrations. In result the near-surface regions of all the specimens have been hardened to a great extent due to the inward diffusion of oxygen atoms. The fretting experiments have been conducted in the gross slip regime and the mutual displacements of the contacting surfaces in the friction node and friction coefficient have been recorded continually. The best results (the lowest wear of the specimen and of the counter-specimen as well) and the slowest increase of friction coefficient have been obtained for the 6 h treatment in oxygen-rich atmosphere. These results have been explained with use of SEM and of the X-ray phase analysis. It has been proved by means of those methods that in the case under consideration a thin layer of TiO 2 phase (rutile) has been created on the surface of the specimen of Ti-6Al-4V alloy. The TiO 2 layer has not been detected after the diffusion treatments in the atmosphere poor in oxygen. r
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.
Transactions of the Indian Institute of Metals, 2013
This paper reports the wear characteristics of the ceramic coatings made with Al 2 O 3 and also with SiC which were performed using atmospheric plasma spraying technique on the Ti-6Al-4V biomedical alloy with the aim of improving their tribological behavior. The wear behavior of the coatings was evaluated using reciprocatory wear tester with coated substrate as the flat and alumina ball as a friction partner in simulated body fluid (Hank's solution) environment. The microstructure and phase composition of the ceramic powders and as-sprayed coatings have been characterized using scanning electron microscope and X-ray diffractometer. Porosity, microhardness, adhesion strength and roughness of the coatings were measured as they have a bearing on wear and friction behavior. The results indicate that plasma sprayed Al 2 O 3 coating exhibits higher wear resistance compared to that of plasma sprayed SiC coating. The higher wear resistance of Al 2 O 3 coating is attributed to the improved melting and spreading of the alumina particles onto the substrate yielding increasingly bonded splats, resulting in compact and dense microstructure with lower porosity and higher microhardness.
Impact wear resistance of plasma diffusion treated and duplex treated/PVD-coated Ti–6Al–4V alloy
Surface and Coatings Technology, 2012
In this paper dynamic ball-on-plate impact wear testing is utilised to evaluate the intrinsic fatigue strength of the surface of triode plasma diffusion treated, single-layered TiN-, CrAlN-, and WC/C-coated and duplex diffusion treated/PVD-coated Ti-6Al-4V. The test is used to assess the resistance of surfaces to dynamic, highcycle loading caused by the repeated impact of a cemented carbide ball. The subsequent observation and comparison of the wear craters produced (and their measured volumes) was used to identify which diffusion treatment (or treatment/coating combination) provided the most marked reduction in contact-induced deformation and overall improvement in wear behaviour. A combination of nanoindentation, Knoop hardness microindentation, scratch adhesion, stylus profilometry, optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and atomic force microscopy test and evaluation methods, was used to characterise the surfaces under investigation. Experimental results revealed that triode plasma diffusion treatments can provide exceptional improvements in the impact fatigue resistance, particularly when the diffusion process has been designed to maximise the resultant hardened case depth. Also, amongst the three coatings tested, PVD CrAlN was found to be the most suitable for applications involving such dynamic impact loading. Finally, the results presented show that an appropriate sequential triode plasma oxidation and nitriding diffusion pretreatment, in combination with a hard and tough PVD ceramic coating, can provide a significant reduction in surface impact wear when compared to either plasma diffusion treatments alone, or PVD ceramic coatings deposited on non-pretreated Ti-alloy substrates.
Dry wear and friction behaviour of plasma nitrided Ti–6AL–4V alloy after explosive shock treatment
Tribology International, 2007
The unlubricated wear behaviour of explosive shock treated and, subsequently plasma nitrided Ti-6Al-4 V alloy was studied using a ball-on-disc wear tester. Plasma nitriding was carried out at three different temperatures (700, 800 and 900 1C) for 3, 6, 9 and 12 h. Plasma nitriding after explosive shock treatment enabled a reduction in the wear rate of two orders of magnitude. Detailed investigations of this improved wear performance dependent on the nitriding temperature and time were carried out. The friction and wear data showed a clear breakthrough transition from the nitrided layer to the core of the Ti-6Al-4 V alloy matrix. The lowest wear volume was obtained for the sample, nitrided at 900 1C for 12 h, especially at loads of 2.5, 5 and 7.5 N. Obviously, the hard nitride layers were intimately associated with low wear rate, providing a smooth low friction surface. The coefficient of friction reduced from 0.46 to 0.2 due to a thick and hard compound layer resulting from a high nitrogen diffusion rate caused by explosive shock treatment that expected to increase point defects in the alloy. Detailed examination of the wear tracks showed that plasma nitriding changes the mechanism of wear from one of adhesion for untreated Ti-6Al-4 V to both delamination and mild abrasive.
Surface modification of Ti–6Al–4V alloys using triode plasma oxidation treatments
Surface and Coatings Technology, 2012
In this study, triode plasma oxidation (TPO) has been used to improve the tribological characteristics of Ti-6Al-4V. The effect of TPO on ball-on-plate reciprocating-sliding, impact, and micro-abrasion wear resistance of this alloy is investigated. Surface micro-profilometry, nano-/micro-indentation hardness testing, scratch-adhesion testing, scanning electron microscopy (SEM), atomic force microscopy (AFM), glancing-angle X-ray diffraction (GAXRD), and glow-discharge optical emission spectroscopy (GDOES) data is presented to corroborate the effects of the oxidation process. 'Traditional' thermal oxidation processes were used to benchmark this novel treatment. Following TPO treatment at 700°C for only 4 h, a hard (exceeding 11 GPa) and well-adhered oxide layer, composed of mixtures of the anatase and rutile polymorphs of TiO 2 , was formed at the surface of the Ti-alloy. This layer is accompanied by a much larger oxygen-solution strengthened zone which creates a gradual chemical and mechanical gradient from the hard oxide 'compound layer' into the ductile substrate core. The various wear testing methods employed revealed excellent wear resistance of the TPO-treated alloy-compared both to the untreated alloy and to conventional, thermally oxidised samples.
IEEE Transactions on Plasma Science, 2000
Although titanium and its alloys own good mechanical properties and excellent corrosion resistance, these materials present poor tribological properties for specific applications that require wear resistance. In order to produce wear-resistant surfaces, this work is aimed at achieving improvement of wear characteristics in Ti-Si-B alloys by means of high temperature nitrogen plasma immersion ion implantation (PIII). These alloys were produced by powder metallurgy using high energy ball milling and hot pressing. Scanning electron microscopy (SEM) and X-ray diffraction identified the presence of α-titanium, Ti 6 Si 2 B, Ti 5 Si 3 , TiB and Ti 3 Si phases. Wear tests were carried out with a ball-on-disk tribometer to evaluate the friction coefficient and wear rate in treated and untreated samples. The worn profiles were measured by visible light microscopy and examined by SEM in order to determine the wear rates and wear mechanisms. Ti-7.5Si-22.5B alloy presented the highest wear resistance amongst the untreated alloys produced in this work. High temperature PIII was effective to reduce the wear rate and friction coefficient of all the Ti-Si-B sintered alloys.
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.