Tadeusz Wierzchoń

Improvement of titanium alloy for biomedical applications by nitriding and carbonitriding processes under glow discharge conditions

Although titanium alloys are used in medicine, they present low wear resistance. In this paper we present the results of studies on surface layers produced by nitriding at three different temperatures, and by carbonitriding under glow discharge conditions in order to improve wear resistance, hardness, and to modulate microstructure and chemical composition of surface layers. A cell culture model using human fibroblasts was chosen to study the effect of such treatments on the cytocompatibility of these materials. The results showed that nitrided and carbonitrided surface layers were cytocompatible. Modulation of surface microstructure by temperature in the nitriding process and chemical composition of surface layers by carbonitriding led to differences in cellular behaviour. Cell proliferation appeared to be slightly reduced from the 6th day of culture on nitrided surfaces produced at 730 °C and 1000 °C, however after 12 days of culture, the best growth was on surface layers produced at 850 °C. The best viability was observed on the carbonitrided layer. The orientation and shape of the cells corresponded to surface topography. Nitriding and carbonitriding under glow discharge conditions may constitute interesting techniques allowing the formation of surface layers on parts with sophisticated shapes. They may also permit modulating surface topography in a way improving the features of titanium alloys for various applications in medicine.

Corrosion resistance of chromium nitride and oxynitride layers produced under glow discharge conditions

Abstract The paper presents the results of investigations of the structure and corrosion resistance of chromium nitride, oxynitride and oxide layers produced on steels by electrochemical chromium deposition combined with glow discharge assisted nitriding, oxynitriding and oxydizing processes. The layers obtained were of the types: CrN+Cr2N+Cr+(Cr,Fe); Cr2N+Cr+(Cr,Fe); CrN+Cr2N+Cr+(Cr,Fe)7C3; Cr2N+Cr+(Cr,Fe)7C3; Cr(N,O)+Cr+(Cr,Fe)7C3 and Cr2O3. The corrosion resistance of the layers is high and can be modified by changing the process parameters, such as the temperature and chemical composition of the gas atmosphere.

The influence of glow discharge nitriding, oxynitriding and carbonitriding on surface modification of Ti-1Al-1Mn titanium alloy

Recent surface treatment studies show that titanium alloys should have an improved resistance to frictional wear and fatigue strength limit without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface nitrided, oxynitrided and carbonitrided diffusion layers. This paper presents the results of metallographic examinations, corrosion and wear resistance tests, surface chemical composition investigation, as well as rotating and bending fatigue tests. These surface treatments increase the useful properties of the titanium alloy. The influence of treatment time and the thickness of the layers on its properties are also investigated.

Wear and corrosion properties of TiN layers deposited on nitrided high speed steel

The susceptibility of high alloyed tool steel, prenitrided under glow discharge conditions and then covered with plasma-assisted chemical-vapour deposited TiN formed at different gas flow rates, to wear and corrosion has been found to depend on both the structure and properties of the surface TiN layer and the chemical composition and properties of the substrate. Nitrogen from the steel surface assists in the TiN formation and this process affects the structure and hardness of the nitrided layer and the structure of the TiN deposit. Depletion of the steel surface in nitrogen during TiN formation may improve the wear resistance but deteriorates the corrosion resistance. By appropriate combination of nitriding and TiN deposition parameters, the optimum combination of wear and corrosion properties could be achieved.

Properties of surface layers on titanium alloy produced by thermo-chemical treatments under glow discharge conditions

Abstract The recent rapid progress in surface treatment techniques dictates that the titanium alloys should have an improved resistance to frictional wear without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface layers of specified microstructure and phase composition. The present paper describes a modification of the plasma discharge nitriding treatment of titanium alloys, i.e. the glow discharge-assisted oxycarbonitriding, which by introducing oxygen, nitrogen and carbon into the surface zone of the layer [a Ti(NCO) type layer improves its useful properties, primarily the resistance to frictional wear and the resistance to corrosion [1,2]. This is because titanium shows a good affinity to oxygen, carbon and nitrogen, whereas the chemical composition of the layer depends on the chemical composition of the low-temperature plasma that forms under the conditions of glow discharge. The present paper also discusses the results of the corrosion behaviour of the OT4-0 titanium alloy in simulated human body fluids before and after the sterilization process. The isothermal and cyclic plasma nitriding and carboxynitriding processes on titanium alloys can be carried out in a specially modified glow discharge chamber designed for the plasma nitriding process.

The formation of Ti(OCN) layers produced from metal—organic compounds using plasma-assisted chemical vapour deposition

Abstract The paper describes the conditions necessary for producing surface layers on steel from Ti(OiC 3 H 7 ) 4 + H 4 + 2 mixture using plasma-assisted chemical vapour deposition. It presents the results of metallographic and scanning microscopy examinations and of electron probe microanalysis. The hardness, the wear resistance measured by the “three-rollers-taper” technique and the corrosion resistance measured using a potentiodynamic test are also given.

Properties of surface layers produced on the Ti–6Al–3Mo–2Cr titanium alloy under glow discharge conditions

The recent rapid progress in surface treatment techniques requires that titanium alloys should have an improved resistance to frictional wear without any loss of their high corrosion resistance. These requirements can be satisfied by producing surface layers of specified microstructure and phase composition. The paper presents the results of examinations of the structure and properties of surface layers formed on the Ti)6Al)3Mo)2Cr titanium alloy by glow discharge assisted nitriding and modified process known . as carbonitriding characterized by an alteration of the gaseous atmosphere in which the process is conducted . The investigations included: metallographical examinations, determination the phase and chemical composition of the layers, measurements of their corrosion and frictional wear resistance and scratch tests. The carbonitriding process increases the hardness and improves the wear and corrosion resistance compared to the nitriding technique. Q 2000 Elsevier Science B.V. All rights reserved.

Morphology of titanium nitride produced using glow discharge nitriding, laser remelting and pulsed laser deposition

Surface layers, produced on titanium alloys by means of glow discharge nitriding, laser modification by remelting using Nd:YAG or diode lasers in nitrogen environment and pulsed laser deposition by titanium target ablation in nitrogen environment, have been studied. Residual stresses were measured using an X-ray method and their values were related to the type of the applied technological process.

Regular paperEffect of nitrogen ion implantation on the structure and corrosion resistance of OT-4-0 titanium alloy

This work presents data on the properties of the surface layer of OT-4-0 titanium alloy after nitrogen implantation. Polished samples were implanted with nitrogen doses of 1 × 1017 and 6 × 1017 cm−2. The corrosion resistance was examined by the potentiodynamic method in 0.5 M NaCl and 15% H2SO4 solutions. Transmission electron microscopy was used to investigate the microstructure of the implanted layers formed on OT-4-0. It was found that the implanted layers consist of a dispersion of fine TiN particles in a deformed matrix of α-Ti. Nitrogen implantation increases the corrosion resistance and microhardness.

Structure and Properties of Ti-Al Intermetallic Layers Produced on Titanium Alloys by a Duplex Treatment

The rapid progress in engineering enhances the demands set on materials requiring better mechanical properties, resistance to frictional wear, corrosion and erosion etc. These demands can be also satisfied by e.g. applying various surface engineering techniques which permit modifying the microstructure, phase and chemical composition of the surface layers produced on the treated parts. A prospective line of the development is the production of the intermetallic layers by combining various methods aimed to improve essentially the performance properties and service life of the treated parts. The paper presents properties of the Al2O3+TiAl3+TiAl+Ti3Al type layer produced on titanium alloy Ti6Al2Cr2Mo by duplex method combined with magnetron sputtering process of aluminium coating with a glow discharge assisted treatment. The results of the examinations: microstructure, chemical and phase composition, frictional wear resistance and mechanical properties are discussed. Produced composite surface layers have the diffusion character and a precisely specified structure, chemical and phase composition and good wear and corrosion resistance what can widen significantly application range of treated parts.