Search

In this work, two kinds of silicon nitride-based composites, namely, those with titanium nitride or silicon carbide additives, were sintered using the hot pressing technique (HP). The phase composition, microstructure, and mechanical and elastic properties of the materials were characterized. Three-dimensional geometric models of the composites were created on the basis of microstructure parameters. Using these models, bulk residual thermal stresses were calculated by the finite element method (FEM). Surface stresses were determined using the XRD method of sin2ψ.

This paper presents how various additions of Al2O3 nanoparticles in the electrolytic bath modified the Ni/Al2O3 nanocomposite coating microstructure. The residual stresses, lattice defects, and crystallographic texture of the obtained deposits were studied. The investigations showed that the tensile residual stresses corresponded to the ceramic nanoparticles content in the deposited coating. The high level of measured stresses in the Ni/Al2O3 coatings indicated the presence of strengthening mechanisms caused by the Al2O3 nanoparticles. The density of crystal lattice defects and grain refinement contributed to the strengthening of the Ni matrix. The main texture components and lattice parameters were more sensitive to deposit thickness changes than to the amount of alumina nanoparticles embedded in the coatings. The Ni/Al2O3 with the smallest thickness showed the highest lattice parameters of the Ni matrix.

This article is a review of important material requirements for hip biomaterials including their response to the body environment (biocompatibility), mechanical properties, wear resistance, fretting corrosion and availability as well as the price. The application of proper biomaterials for hip implants is one of the major focal points in this article. Background information is also provided on metals used in other prosthetic devices and implant components. Titanium and its alloys, cobalt base alloys and stainless steels (bio-steels) are used for load-bearing hip implants. These three groups of metallic materials will be introduced and discussed in detail. Metals and their alloys are crystalline materials since their properties depend on the crystal lattice, chemical and phase compositions, grain size, lattice defects, crystalline texture and residual micro- and macro-stresses. All these features of biomaterials are formed during technological manufacturing, such as metallurgical process, solidification, plastic deformation (rolling and forging), machining, heat treatment and coating. All these technological processes work in optimal conditions in order to achieve the optimal microstructure and mechanical, chemical and biological properties. Amongst the above-mentioned particular properties of biomaterials, fretting is a major concern as regards hip implants at the femoral head and neck taper interface. Additional important mechanisms of interaction between the implant and the human body must be taken into account, i.e. diffusion stream of foreign particles and atoms from the implant to body fluids, to the tissue and to the bone. These foreign particles and atoms are released from the implant to the body fluid, to the tissue and to the bone as wear product during use. All together they contribute to the wear, i.e. loss of weight, strength or volume of hip components. Wear rates of ultrahigh molecular weight polyethylene mated against Ti-6Al-4V are significantly greater than the ones for Co-Cr-Mo alloys. Therefore, thermochemical surface treatments like diffusion ion nitriding should be applied to increase the resistance of titanium alloys to wear. Austenitic stainless steels are also used for temporary applications, but they have lower resistance to pitting corrosion than titanium and cobalt alloys. The purpose of the paper is to introduce a group of metallic materials, which is often chosen for surgical hip implants. Conclusions of the paper refer to information which support important medical and patient decisions on hip implants. Also, the development of biomaterials, their treatments, properties, surface layers and coatings are considered. All these features develop over time and need synergy and experience in the progress of the biomedical, mechanical and materials science.

The goal of the work was to investigate the crystallization process of silica–strontium–barium glass from cathode ray tube (CRT) modified by various TiO2 additions (18–23 mass%). The control thermal treatment of the parent glass with nucleating agent leads to the crystallization. The crystalline phases were determined by X-ray diffractometry. The microstructures of the heat-treated samples were studied by the SEM/EDS technique. Glass ceramic samples were obtained by the heat treatment of CRT glasses with 18 and 23 mass% of TiO2 in a gradient oven. Thermal characteristics such as the glass transition temperature T g, the temperature of non-isothermal crystallization T c, and the thermal stability parameter were determined by DTA/DSC. The linear expansion coefficients of the glasses as a function of temperature were measured. Based on the DTA results, we found that TiO2 was effective in decreasing the crystallization temperature.

The effects of thermo-mechanical treatment on selected properties related to the structure of Fe-0.85Mo-0.65i-1.4C powder metallurgy (PM) steel are reported. Three kinds of initial microstructure of specimens, i.e., pearlite + ferrite + cementite, martensite + retained austenite and α + spheroidized cementite were examined. Processing was carried out on a plastometer-dilatometer Bahr machine by compression cylindrical specimens at 775 °C at a strain rate of 0.001 s−1. X-ray diffraction was carried out with symmetrical Bragg-Brentano and grazing incident angle methods on a D8-Advance diffractometer with filtered radiation of cobalt CoK α . The following features were determined: texture, density of dislocations, density of vacancies, lattice parameter of Fe α and mean size of crystallites. Significant differences in structure were observed, especially in quenched specimen, as a result of the thermo-mechanical treatment. Regardless of initial state of the specimens, the determined properties were on a similar level. Crystallite size was in the range 97-106 nm, crystallite texture (I{200}/I{110}) × 10 = 1.15-1.62 and density of vacancies I{110}/I{220} = 7.06-7.52.

This paper presents the properties of plasma and HVOF thermally sprayed coatings obtained by blending the NiCrBSi and Fe2O3 powders. Although the blended powders differ in particle size, shape, and distribution, it is possible to obtain composite coatings with a NiCrBSi matrix containing iron oxides. Except for a different microstructure, plasma and HVOF coatings have a different phase composition. An addition of Fe2O3 powder in the mixture with NiCrBSi powder led to a significant increase in roughness of the coating sprayed both in a plasma and supersonic manner. The coefficient of friction, microhardness and roughness of the coatings was determined using an experimental design called PS/DS-P:24 − 1 program. The study shows that the HVOF-sprayed coatings had a lower coefficient of friction.

Influence of the electrodepositing parameters e.g. applied electric current as variable on texture formation and on mechanical properties of copper thin films was studied. Experiment was done for copper deposition from sulphate bath under galvanostatic and pulse current. It was found that copper layers exhibits different texture depending on applied current conditions during electrodepositing process. Pulse and direct current conditions leads to different texture of electrodeposited copper. Texture of electrodeposited copper coatings and mechanical properties could be correlated. It was found that, texture indexes although are not complex information about texture could be used for analysis of such correlation in technological process.

Electrodeposition and other methods are employed to obtain metallic films and coatings. Copper coatings are most extensively used in circuit board industry and often as a base to further formation of other metallic films. Electrodeposited copper films (thin layers) are widely used in electronic and automotive industry so its electrical and mechanical properties and its thickness are important. Several methods are used for thickness determination of thin films and coatings for example mechanical, magnetic and ball crater with light microscopy methods. They are destructive and not precise enough. The X-ray fluorescence, absorption and diffraction are more frequently used due to better precision. Although they are complex and expensive, they pronounce an important feature like non-destructive character. For particular cases geometrical conditions and mathematical calculation procedure must be elaborated. An application of X-ray diffraction in grazing incidence angle for thickness determination is described in this article. The method is based on absorption principles of X-ray beam. The absorption is proportional to thickness of the coating and to incidence and to the diffraction angle which. Geometrical conditions were obtained experimentally and suitable mathematical calculations were introduced. The elaborated methodical approach was applied to thickness determination of copper coatings electrodeposited on a brass substrate.

The new hybrid method, which combines the laser alloying process with slide burnishing, was investigated and presented in the work. Both treatments were performed on the laser stage in one operation. The experiments were done on carbon steel alloyed with cobalt stellite. The alloying process was conducted with continuous laser CO 2 , at different parameters. The single- and multiple-path processes were investigated. The microstructure, microhardness and residual stresses of surface layer after the laser alloying process and laser alloying combined with burnishing were presented. The results of the experimental studies have shown that the proposed new hybrid method allowed for the generation of compressive stresses in surface layer of the alloyed material. The structural analysis has proven that the burnishing process had caused deformation of grains in the 20–30 μm thick zone and increased microhardness of the surface zone material. The X–ray diffraction measurements of residual stresses in surface layer of the samples subjected to the alloying process and burnishing, both in cold and hot conditions, were performed. In the case of multiple-path laser alloying treatment the tensile stresses, approximately 500 MPa, were obtained at the surface. Multiple alloying combined with burnishing generated compressive stresses of about −600 MPa at the surface, substantially improving the surface layer.

The non-destructive structure characterisation of surface layers for various kinds of ball bearings can be a powerful method in surface characterization and in quality control. The ball bearings were made of 100Cr6 steel and they were superfinished and mechanically burnished. An application of classical X-ray diffraction sin2ψ method and classical Bragg-Brentano diffraction geometry in these kinds of surface examinations make some problems in term of X-ray real depth of penetration. An application of methods based on grazing angle X-ray diffraction geometry, made possible to get real value of residual macro-stresses, retained austenite and additionally could be suitable in estimation of their gradient-like distribution versus depth under surface. An application of this geometry to X-ray diffraction phase analysis enabled to get phase contents versus thickness under surface in non-destructive way as well. The results are not infected by gradient-like distribution. The X-ray quantitative phase analysis was used to establish volume fraction of transformed retained austenite. Theoretical calculation of residual macro-stresses due to volume fraction of transformed austenite in ball bearings and following measurements of residual stresses were curried out as well. The mechanical burnishing of ball bearings caused big compressive residual stresses about – 1000 MPa and phase transformation of austenite in thin surface layer. These factors can influence on properties of following exploitation and durability.

The residual stress field in a titanium nitride coating was determined using the X-ray diffraction method based on grazing incident angle geometry. The first order stress components were determined in TiN coating on WC and on steel substrates. The diffraction elastic constants calculated by the self-consistent method were used for the interpretation of the results. The advantages of the grazing incidence geometry are pointed out in the case of the examination of heterogeneous residual stresses in thin layers.

The microstresses in polycrystalline material were determined by diffraction technique. Using the modified sin 2 ψ method the plastic incompatibility stresses in a cold rolled steel were estimated. The grazing incidence angle geometry was used for measurement of non-uniform stresses in the near surface volume of Ti sample. The later method allowed to determine the microstresses induced due to anisotropy of thermal expansion coefficient.

The intermetallic compounds of the Ni–Al, Cu–Al and Cr–Al systems are characterised by the profitable set of mechanical and physical properties, such as good abrasion resistance, high temperature oxidation and sulfur corrosion resistance. Alloy powders, among them intermetallic powders, are widely used and methods of their production are under development. The technology described here takes advantage of a natural phenomenon, i.e. self-disintegration which takes place in alloys containing Al4C3 carbide, e.g. in high aluminium cast iron. The result of chemical reaction between this carbide and moisture are products of bigger volume. It causes cracking of the matrix, i.e. self-disintegration into a powder. The physical–chemical principles of the powder production using self-disintegration are presented in this article. In Ni–Al–C, Cu–Al–C and Cr–Al–C alloys, Al4C3 phase is not present in the liquid melt. Therefore, the presence of a catalysing component, increasing the chemical activity of carbon, is required. Iron can be one of such additions. The mechanism of the influence of the iron on the Al4C3 carbide crystallisation and the physical–chemical properties of the powders obtained by the self-disintegration process is presented in this work. Applications (plasma spraying, powder metallurgy) of the intermetallic powders obtained in this way are mentioned.

A new development in the determination of residual stresses in thin surface layers and coatings is presented. The procedure, based on the grazing-incidence X-ray diffraction geometry (referred to here as the `g-sin2 ψ' geometry), enables non-destructive measurement at a chosen depth below the sample surface. The penetration depth of the X-ray radiation is well defined and does not change during the experiment. The method is particularly useful for the analysis of non-uniform stresses in near-surface layers. The g-sin2 ψ geometry was applied for measurements of the residual stresses in TiN coatings. Anisotropic diffraction elastic constants of textured material were used to determine the stress value from the measured lattice strains. A new method of data treatment enables reference-free measurements of residual stresses.

The paper presents the results of high-energy grinding in the electro-magneto-mechanical (EMM) mill. Ground powder is treated in a very specific and intensive way owing to several field forces operating simultaneously in the EMM mill. The grinding power in the centre of the mill's working chamber is in the order of 2 MW/m3, which is much more than in ordinary mills. Therefore, the grinding time is very short, i.e., several tens of seconds. The self-disintegrated Fe–Al–Si powders of 155 μm on average undergo size reduction to 8 μm after 120 s. Over 25% of the total weight get the size of less than 1.3 μm. Very hard materials, such as SiC and B4C reduce their grain size over 30 times after 120 s of grinding in the EMM mill. The results of the grinding of Fe2O3 powder are even better. In ball mills, vibration and planetary mills, similar results can be achieved after a period several hundreds times longer. The treatment of Fe–Al–Si powder presented here is intended as the preparation procedure for sintering, plasma spraying or laser surface alloying.

The kind of bonding phase has a significant influence on the microstructure and mechanical properties of diamond compacts. Microstructural studies of diamond with 5% wt. Ti and 5%wt. Tic (and also 30%wt. Tic) were carried out with a Transmission Electron Microscope. The TEM microstructural observations show differences between the metal and metal carbide bonding phase in diamond compacts. The mismatch of thermal expansion coefficients between diamond and the bonding metal or the compound induces significant internal stresses and may generate micro-cracks in polycrystalline diamond compacts. Twins and dislocations are the important details of microstructures in diamond crystals after HPHT sintering. They can appear as a result of residual stress relaxation. Results of measurements of residual stresses on a diamond compact surface by means of the “sin2ψ X-ray diffraction method are reported.

Conversion electron Mossbauer spectra and X-ray diffractograms for samples of ball-bearing steel were measured. After heat treatment, samples were subjected to contact fatigue with the stress either lower or higher than the contact fatigue strength. The relative contributions of the retained austenite, martensite and carbide phases after consecutive fatigue tests were determined. It was found that the fraction of retained austenite decreases sharply with the number of fatigue cycles and that the effect is more pronounced for penetration depths of up to 100 nm into the sample as observed using conversion electron Mossbauer spectroscopy than that for penetration depths of up to 10 μm into the sample as determined using X-ray analysis.