Wear Resistance of Ti–6Al–4V Alloy Ball Heads for Use in Implants

The effect of thermohydrogen treatment and vacuum ion–plasma nitriding on the determination of the volume and surface structure of ball heads made of Ti–6Al–4V alloy was studied. It was found that the submicrocrystalline structure formed in the head during thermohydrogen treatment makes it possible to achieve hardness values of 39–41 units HRC and a surface roughness of 0.02 μm. It was shown that the creation of a modified layer consisting of ε (TiN) and δ (Ti2N) titanium nitrides on the surface of a ball head and the solid interstitial solution of nitrogen in α-titanium makes it possible to completely eliminate material wear when testing for friction on ultra-high-molecular-weight polyethylene. The equivalent analysis was also conducted with a ball head that had been implanted in a human body for 12 years. It was found that the change in the color of the head, from slightly golden after nitriding to metallic, is due to the formation of an oxynitride nanoscale layer on the surface. It was shown that in contrast with films made of titanium oxide, the film developed in this study has high wear resistance.

Mechanical and Tribological Behaviors of Nanocomposite Titanium Nitrides Coatings

TiN coatings with a thickness of 2 μm were deposited using the magnetron sputtering has developed rapidly over the last decade in such a way that it has become an established process of choice for the deposition of a wide range in various applications for different domains as it gives excellent performance in many aspects. In view of this, we have deposited the TiN coatings by magnetron sputtering using Ti target at different nitrogen content to study the influence of the nitrogen content on the mechanical properties and tribological behaviors of the TiN coatings were systematically investigated using nanoindentation and a pin-on-disk tribometer. Nanoindentation results shows that the hardness and Young's modulus of the TiN coatings increase with increasing N content in the coatings.Wear test results indicate that the wear rate and friction coefficient of the XC100 steel substrate were significantly reduced by deposition of the TiN coatings, and the tribological behaviors of the TiN coatings are strongly dependent on the nitrogen content in the coatings.

On the disperse acicular ferrite formation in the structure of cold-resistant joints under temperatures up to –70°С in MMA welding of 10KhSND steel. Part 1

The article presents an analysis of the metallurgical techniques that provide high quality electrodes for manual arc welding of low-carbon low-alloyed cold-resistant steels. It is shown that it is possible to improve technological and operational properties of welded joints at very low climatic temperatures up to –70°C implementing micro-alloying of the weld metal with nitrogen, titanium, cerium oxide and diamond nanopowder produced by detonation synthesis. The composition introduced into the electrode coating modifier mixture is identified. The cumulative effect of its components on the weld impact strength under temperature testing within the range from –20 up to –70°C was established. The matrix of the weld metal is composed mainly of disperse acicular ferrite, hardened by nanoparticles allegedly nitrides and carbonitrides of titanium and aluminum. It is shown that the centers for the crystallization of acicular ferrite are micro-sized non-metallic inclusions formed on ultrafine titanium nitrides. It was revealed that the toughness of the weld metal at low climatic temperatures is higher than toughness of joints welded by massively imported Japanese KOBELCO electrodes LB-52U. The results of the study make it possible to increase the cold resistance of welded structures for petrochemical plants and other facilities located in the Extreme North of the Russian Federation.Part 2 of the article will be devoted to the study of the welding and technological properties of coated electrodes.

Analysis of Microstructure and Properties of a Ti–AlN Composite Produced by Selective Laser Melting

Selective Laser Melting (SLM) is a manufacturing technique that is currently used for the production of functional parts that are difficult to form by the traditional methods such as casting or CNC (Computer Numerical Control) cutting from a wide range of metallic materials. In our study, a mixture of commercially pure titanium (Ti) and 15% at. aluminum nitride (AlN) was Selective Laser Melted to form three-dimensional objects. The obtained 4 mm edge cubes with an energy density that varied from 70 to 140 J/mm3 were examined in terms of their microstructure, chemical and phase composition, porosity, and Vickers microhardness. Scanning Electron Microscopy (SEM) observations of the etched samples showed inhomogeneities in the form of pores and unmelted and partly melted AlN particles in the fine-grained dendritic matrix, which is typical for titanium nitrides and titanium aluminum nitrides. The AlN particles remained unmelted in samples, but no porosity was observed in the interface area between them and the dendritic matrix. Additionally, samples fabricated with the presintering step had zones with different sizes of dendrites, suggesting a differing chemical composition of the matrix and the possibility of the formation of the phases forming an Ti–Al–N ternary system. The chemical composition in the microareas of the samples was determined using Energy Dispersive X-Ray Spectroscopy (EDS) and revealed differences in the homogeneity of the samples depending on the SLM process parameters and the additional presintering step. The phase composition, examined using X-ray Diffraction analysis (XRD), showed that samples were formed from Ti, TiN, and AlN phases. Porosity tests carried out using a computer microtomography revealed porosities in a range from 7% to 17.5%. The formed material was characterized by a relatively high hardness exceeding 700 HV0.2 over the entire cross-section, which depended on the manufacturing conditions.

A molecular dynamics study of nanoscale titanium nitrides formation in ferrite

Molecular dynamics simulation was adopted to investigate the nanoscale titanium nitride formation at the early formation stage in high-strength low-alloy steel. During the cluster formation process, the nitride clusters were formed through the atom aggregation. The atomic interactions of titanium and nitride atoms were revealed and the cluster property was discussed. The nanoscale titanium nitride clusters own a wide composition, and the cluster formation mechanism was concluded.

First-principle calculations of ternary compounds: Immm-BxTi3−xN2

Boron nitride (BN) and Titanium nitrides (TiNs) have been successfully researched recently. In order to analyze the relationship among the Boron, Nitrogen and Titanium, the ternary compounds with an orthorhombic structure Immm- are studied. We further researched on the mechanical, electronic and optical properties of new Immm-B[Formula: see text]Ti[Formula: see text]N2 ([Formula: see text]). The structures of BTi2N2 and B2TiN2 are mechanically stable at 0, 50 and 100 GPa. The BTi2N2 has the higher cutting resistance and better ductility than the B2TiN2. The higher Young’s modulus of B2TiN2 indicates the B2TiN2 is stiffer than BTi2N2. The BTi2N2 is harder to compress in the [Formula: see text] direction and the B2TiN2 is harder in [Formula: see text] direction. Immm-BTi2N2 and B2TiN2 have good metallicity at 0 and 100 GPa. Immm-BTi2N2 has the higher dielectric function than B2TiN2 and the plasma frequency of B2TiN2 is bigger than that of BTi2N2. We hope our work will provide some help to the experimental work about the technology of the material.

Complex Saturation of Titanium Alloys with Boron, Chromium and Titanium

This work described the technology of boronizing of titanium Grade2 from the generation of the gas phase directly in a sealed container during the decomposition reactions of the powder saturating medium. With such an implementation of the process in a closed volume, waste gas neutralization devices are not required, since the generation and decomposition of active saturating gases occurs in a closed volume. At saturation of titanium from the gas mixture, titanium borides, titanium nitrides, as well as titanium and chromium carbides can be produced in the coating. The microhardness of the coating is 2800–3200 HV0.1. The thickness of the diffusion coatings in this case can be up to75 microns. It is indicated that diffusion coatings on titanium by this technology should not exceed a thickness of more than 100 microns, and if the thickness of the diffusion coating exceeds 100 microns, the risk of chipping will increase.

Wetting properties of titanium oxides, oxynitrides and nitrides obtained by DC and pulsed magnetron sputtering and cathodic arc evaporation

Thin films of titanium oxides, titanium oxynitrides and titanium nitrides were deposited on glass substrates by the methods of direct current (DC) and pulsed magnetron sputtering and cathodic arc evaporation. Phase analysis of the deposited films by X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FT-IR) showed the presence of phases with various Ti oxidative states, which indicated a high concentration of oxygen vacancies. The films morphology was investigated by scanning electron microscopy (SEM). Investigations of the films wettability, either with water or ethylene glycol, showed that it depends directly on the concentration of oxygen vacancies. The wettability mechanism was particularly discussed.