Shaping the structure and properties of titanium and Ti6Al7Nb titanium alloy in low-temperature plasma nitriding processes

Tarnowski, Michał; Borowski, T.; Skrzypek, Sławomira; Kulikowski, Krzysztof; Wierzchoń, T.

doi:10.1016/j.jallcom.2021.158896

Cited by 28 publications

(17 citation statements)

References 29 publications

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“…It is characteristic for the PN process that the nodules are the coarser, the higher the nitriding temperature, while the bright spots representing point surface defects remain practically the same. The cross-section scanning and transmission electron microscopy (SEM/TEM) investigations not only confirmed the presence of a surface undulation representing the nodular features, but also proved that they increase with the PN temperature both for the Ti-6Al-4V [8] and Ti-6Al-7Nb [2,9] alloys. However, none of the images published so far gave any indication of the nature of the point-like objects observed with the SEM method.…”

Section: Introductionmentioning

confidence: 61%

(Ti,Al)O2 Whiskers Grown during Glow Discharge Nitriding of Ti-6Al-7Nb Alloy

et al. 2021

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Plasma nitriding of titanium alloys is capable of effective surface hardening at temperatures significantly lower than gas nitriding, but at a cost of much stronger surface roughening. Especially interesting are treatments performed at the lower end of the temperature window used in such cases, as they are least damaging to highly polished parts. Therefore identifying the most characteristic defects is of high importance. The present work was aimed at identifying the nature of pin-point bumps formed at the glow discharged plasma nitrided Ti-6Al-7Nb alloy using plan-view scanning and cross-section transmission electron microscopy methods. It helped to establish that these main surface defects developed at the treated surface are (Ti,Al)O2 nano-whiskers of diameter from 20 nm to 40 nm, and length up to several hundreds of nanometers. The performed investigation confirmed that the surface imperfection introduced by plasma nitriding at the specified range should be of minor consequences to the mechanical properties of the treated material.

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Section: Introductionmentioning

confidence: 61%

(Ti,Al)O2 Whiskers Grown during Glow Discharge Nitriding of Ti-6Al-7Nb Alloy

et al. 2021

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“…Decarburization enhances the diffusion of nitrogen into the steel [31] and increases concentration of nitrogen in the layer [25,32] , thus some nitrides in the layer can appeared. Some of the authors [33] also indicate, that nitrogen-rich iron nitrides form during rst hour of the process, even at very low temperature and their presence is related not only to the temperature and time of the process, but also the effect of the cathode sputtering phenomenon, occurring during the heating of the treated samples to the temperature of the nitriding process, which is in uenced by the pressure of gas atmosphere in the working chamber and its chemical composition [34] .…”

Section: Quantitative Chemical and Phase Composition Of Nitrided Layersmentioning

confidence: 99%

Glow discharge nitriding of nanobainitic X37CrMoV5-1 steel

Skołek

Chmielarz

Marciniak

et al. 2023

Preprint

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One of the methods of improving mechanical properties of steels is nanostructuring via austempering, which leads to formation of a nanobainitic microstructure - a fine carbide-free bainitic ferrite plates with retained austenite. Due to high density of grain and interphase boundaries, this microstructure provides high tensile strength. Moreover, high amount of retained austenite guarantees high ductility and fracture toughness. However, retained austenite may also decrease hardness and wear resistance. Thus, to improve the properties of the surface an additional process is necessary. There are several methods of surface engineering which allow to produce hard diffusive layer, however most them are usually carried out at a temperature, in which nanobainite decomposes and loses its high properties. The purpose of the present work was to produce hard and wear-resistant nitrided diffusion layers on nanobainitic X37CrMoV5-1 steel surface during glow discharge nitriding, while keeping microstructure in core of the sample almost intact. Two temperatures of a nitriding were chosen. Obtained results were compared to the layers produced at quenched and tempered substrate to determine the influence of the microstructure of the substrate on the kinetics of the layer’s growth. The microstucture of the layers were described and their properties such as microhardness and wear resistance were investigated.

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“…Due to its lower processing temperatures, plasma nitriding is able to achieve high surface hardness while maintaining the high mechanical properties of the core material. In addition, plasma nitriding allows control the microstructure of the treated workpiece, phase and chemical composition, surface topography, morphology, and residual stresses [46], all of which are critical for determining surface properties, especially if the workpiece is to be used as a part in the human body.…”

Section: Mechanical Propertiesmentioning

confidence: 99%

Effect of pulse frequency on the surface properties and corrosion resistance of a plasma-nitrided Ti-6Al-4V alloy

Kaewnisai,

Chingsungnoen,

Poolcharounsin

et al. 2023

Mater. Res. Express

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In this work, Ti-6Al-4V alloy, commonly used as implant material in biomedical applications, was treated by plasma nitriding. The nitriding process was carried out using an N2-H2 plasma (1000:500 sccm) at an operating pressure of about 866 Pa. The current regulation was about 1.8 A, the negative voltage was about 480-500 V, and the power was 840-940 W. The nitriding temperature was maintained at 650±5 ºC, and the nitriding time was 240 min. Bipolar pulse frequencies were varied at 25, 50, 100, 150, and 200 kHz. Analysis by grazing incidence X-ray diffraction spectrometer (GI-XRD) revealed the presence of δ-TiN and ε-Ti2N phases in all nitrided samples. The hardness depth profile was measured with a penetration depth of about 5 nm using the enhanced stiffness procedure (ESP). The results showed that all the nitrided samples had a surface hardness approximately three times that of the unnitrided sample. This result is consistent with that from glow discharge emission spectroscopy (GD-OES), which confirmed the diffusion distance of nitrogen atoms from the surface of about 5 μm. After plasma nitriding, the surface roughness tended to increase, resulting in an increase in the water contact angle (WCA) and a decrease in the work of adhesion. The specific wear rate (ball-on-disk) of all nitrided samples decreased and was significantly lower at a bipolar pulse frequency of 50 kHz. This result is consistent with the stability of the coefficient of friction (CoF) after 6000 sliding cycles. Moreover, the nitrided sample at 50 kHz exhibited the lowest corrosion current density in artificial saliva based on the Tafel potential polarization method.

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Shaping the structure and properties of titanium and Ti6Al7Nb titanium alloy in low-temperature plasma nitriding processes

Cited by 28 publications

References 29 publications

(Ti,Al)O2 Whiskers Grown during Glow Discharge Nitriding of Ti-6Al-7Nb Alloy

(Ti,Al)O2 Whiskers Grown during Glow Discharge Nitriding of Ti-6Al-7Nb Alloy

Glow discharge nitriding of nanobainitic X37CrMoV5-1 steel

Effect of pulse frequency on the surface properties and corrosion resistance of a plasma-nitrided Ti-6Al-4V alloy

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