TESTING THE COBALT ION EMISSION ON THE STAND FOR DIFFERENT ANGLES OF POSITIONING THE COMPONENTS OF THE METAL–METAL HIP JOINT ENDOPROSTHESIS

The paper deals with the subject related to the assessment of the influence of the axis angle of the metal components of the hip joint on the emission of cobalt ions. The tribological tests were carried out with the use of a simulator for the examination of hip joint endoprostheses, the structure of which enables the fixation of endoprosthesis components in accordance with the anatomical structure of the human hip joint. During the tests, the simulator performs flexion and extension movements as well as loads occurring in the human hip joint while walking. Loss-wear tests were carried out for nine variants of the “head–cup” system settings. These settings were determined on the basis of CT images obtained from patients after arthroplasty. After the tribological tests were completed, samples of the lubricating fluid with the wear products suspended in it were collected in order to determine the concentration of cobalt ions, which was carried out using the atomic absorption spectrometry method. As a result, the influence of the head antetorsion angle (α) and the acetabular anteversion angle (β) on the concentration of cobalt ions was analysed.

Effect of Microstructure and Hardness on Cavitation Erosion and Dry Sliding Wear of HVOF Deposited CoNiCrAlY, NiCoCrAlY and NiCrMoNbTa Coatings

Metallic coatings based on cobalt and nickel are promising for elongating the life span of machine components operated in harsh environments. However, reports regarding the ambient temperature tribological performance and cavitation erosion resistance of popular MCrAlY (where M = Co, Ni or Co/Ni) and NiCrMoNbTa coatings are scant. This study comparatively investigates the effects of microstructure and hardness of HVOF deposited CoNiCrAlY, NiCoCrAlY and NiCrMoNbTa coatings on tribological and cavitation erosion performance. The cavitation erosion test was conducted using the vibratory method following the ASTM G32 standard. The tribological examination was done using a ball-on-disc tribometer. Analysis of the chemical composition, microstructure, phase composition and hardness reveal the dry sliding wear and cavitation erosion mechanisms. Coatings present increasing resistance to both sliding wear and cavitation erosion in the following order: NiCoCrAlY < CoNiCrAlY < NiCrMoNbTa. The tribological behaviour of coatings relies on abrasive grooving and oxidation of the wear products. In the case of NiCrMoNbTa coatings, abrasion is followed by the severe adhesive smearing of oxidised wear products which end in the lowest coefficient of friction and wear rate. Cavitation erosion is initiated at microstructure discontinuities and ends with severe surface pitting. CoNiCrAlY and NiCoCrAlY coatings present semi brittle behavior, whereas NiCrMoNbTa presents ductile mode and lesser surface pitting, which improves its anti-cavitation performance. The differences in microstructure of investigated coatings affect the wear and cavitation erosion performance more than the hardness itself.

Influence of Contamination of Gear Oils in Relation to Time of Operation on Their Lubricity

The quality and reliability of consumables, including gear oils, results in the failure-free operation of the transmission components in heavy trucks. It is known that oil viscosity is essential for all lubricated tribopairs for wear and friction reduction in all vehicles with a gearbox. Viscosity may be influenced by the contamination that wear products can impart on the oil. Oil contamination can also affect lubrication efficiency in the boundary friction conditions in gearboxes where slips occur (including bevel and hypoid gearboxes). The present research focused on this issue. An obvious hypothesis was adopted, where it was theorized that exploiting the contaminants that are present in gear oil may affect how the lubricating properties of gear oils deteriorate. Laboratory tests were performed on contaminants that are commonly found in gear oil using the Parker Laser CM20. The study was designed to identify a number of different solid particles that are present in oil. At the second stage, friction tests were conducted for a friction couple “ball-on-disc” in an oil bath at 90 °C on a CSM microtribometer. The quantitative contamination of the gear oils that contained solid particles and the curves representing the friction coefficients of fresh oils with a history of exploitation were compared. The test results were statistically analysed. Exploitation was shown to have a significant impact on the contamination of gear oils. It was revealed that the contamination and the mileage had no effect on the tested oils.

Analysis of wear particles in used marine engine oils

В данной статье предпринята удачная попытка комплексирования магнитооптического метода и метода фотонной корреляционной спектроскопии для регистрации ферромагнитных частиц продуктов износа дизельного двигателя и определения их дисперсных характеристик. Такой подход позволяет фиксировать низкое содержание магнитных наноразмерных частиц и их дисперсность в отработанном судовом моторном масле, является новым и решает актуальную задачу. Выполнены эксперименты по наблюдению продольного магнитооптического эффекта Фарадея в модельной магнитной жидкости и в отработанном моторном масле. Показано, что низкая концентрация магнитных частиц в отработанном масле не позволяет наблюдать в нем эффект вращения плоскости поляризации в магнитном поле. Для измерения крупных частиц износа, смытых с фильтрующего элемента масляного фильтра, использовались закономерности процесса осаждения частиц в растворе и регистрация поглощения света, изменяющегося со временем. Полученные результаты позволяют получать важную информацию о состоянии и неисправностях деталей и механизмов двигателя по содержанию частиц износа в отработанном масле. In this article, a successful attempt has been made to combine the magneto-optical method and the method of photon correlation spectroscopy to register ferromagnetic particles of diesel engine wear products and determine their disperse characteristics. This approach makes it possible to record a low content of magnetic nanosized particles and their dispersion in used marine engine oil, is new and solves an urgent problem. Experiments on observation of the longitudinal magneto-optical Faraday effect in a model magnetic fluid and in used engine oil have been carried out. It is shown that the low concentration of magnetic particles in the waste oil does not allow observing the effect of rotation of the plane of polarization in a magnetic field. To measure large wear particles washed away from the filter element of the oil filter, we used the regularities of the process of particle sedimentation in solution and the registration of light absorption that changes over time. The results obtained make it possible to obtain important information on the condition and malfunctions of engine parts and mechanisms by the content of wear particles in the used oil.

Study and analysis of the morphology and composition of wear particle in the used engine oil of marine diesel engines

В статье представлены результаты исследования состава и морфологии частиц продуктов износа в работающем моторном масле судового двигателя внутреннего сгорания. Полученные данные базируется на результатах физико-химического и спектрального анализа работающего масла, идентификации дисперсного состава частиц загрязнения в нем и углубленном анализе элементного состава и формы продуктов износа пар трения судовых двигателей. Из представленных результатов следует, что основное количество частиц износа не превышает 3 мкм и представляет собой сложные сплавы, полученные в результате изнашивания трущихся сопряжений двигателя. Анализ формы частиц износа, выполненный с помощью сканирующего электронного микроскопа Lyra3 Tescan, показал что у более чем 90 % всех частиц величина Wr превышает значение 0,8. Показано на основе выполненного исследования, что спектральные методы анализа обеспечивают высокую достоверность трибомониторинга и трибодиагностики судовых дизелей. The article presents the results of a study of the composition and morphology of particles of wear products in used engine oil of a marine diesel engine. The obtained data are based on the results of physicochemical and spectral analysis of operating oil, identification of the dispersed composition of pollution particles in it, and in-depth analysis of the elemental composition and shape of wear products of friction pairs of ship engines. From results follow that the main amount of wear particles does not exceed 3 microns and they are complex alloys obtained as a result of engine wear of friction. The analysis of the shape of the wear particles, carried out using a Lyra3 Tescan scanning electron microscope, showed that more than 90% of all particles had a Wr value greater than 0.8. It is shown on the basis of the performed research that spectral methods of analysis provide high reliability of tribomonitoring and tribodiagnostics of marine diesel engines.

Failure Analysis and the Evaluation of Forced-In Joint Reliability for Selected Operation Conditions

In this article, sample damage and wear of forced-in joints is presented, and their reliability evaluated. Compared were shafts without additional finish treatment, rolled shafts and those with a TiSiN coating. Tribological samples under investigation operated in rotational bending conditions. Recorded was the number of fatigue cycles at which damage might occur. Reliability indicators were plotted, which demonstrated that coated shafts are distinguished by the highest reliability and low damage intensity. Macroscopic observations of shaft surfaces demonstrated the traces of adhesive wear and, in the case of shafts without additional treatment and in the case of rolled shafts, fretting wear traces in the form of a ring comprising the entire shaft circumference. Microscopic observations showed numerous build-ups on the surface, microcracks, and the occurrence of wear products in the gap between the shaft and sleeve. The highest fatigue strength was demonstrated by shafts with a TiSiN coating. The shaft section change area was the place where fatigue wear occurred.

Morphology of the surface of d-transition metal alloys of the IV period after CBN grinding

Studies have been carried out when grinding alloys based on titanium, vanadium, chromium, iron, cobalt and nickel. According to the condition of the neat surface, the alloys are divided into groups. The regularities of changes in the roughness parameters of Ra and Rsm are investigated. The parameter of the average density of the peaks of the grains forming the elements of the surface roughness profile has been introduced, the relationship of the introduced parameter with Ra is shown. It is established that when grinding all alloys, the treated surface is impregnated by the wear products of the abrasive tool. Electronic photographs of objects are given. The possible sizes of embedded crystals are determined.

Ti-Ions and/or Particles in Saliva Potentially Aggravate Dental Implant Corrosion

The corrosive titanium products in peri-implant tissues are a potential risk factor for peri-implantitis. There is very limited information available on the effect of the corrosion and wear products on the dental implant corrosion. Therefore, we determined the influence of Ti-ions and Ti-particles on Ti corrosion. Eighteen commercially pure-Ti-grade-2 discs were polished to mirror-shine. Samples were divided into six groups (n = 3) as a function of electrolytes; (A) Artificial saliva (AS), (B) AS with Ti-ions (the electrolyte from group A, after corrosion), (C) AS with Ti-particles 10 ppm (D) AS with Ti-particles 20 ppm, (E) AS with Ti-ions 10 ppm, and (F) AS with Ti-ions 20 ppm. Using Tafel’s method, corrosion potential (Ecorr) and current density (Icorr) were estimated from potentiodynamic curves. Electrochemical Impedance Spectroscopy (EIS) data were used to construct Nyquist and Bode plots, and an equivalent electrical circuit was used to assess the corrosion kinetics. The corroded surfaces were examined through a 3D-white-light microscope and scanning electronic microscopy. The data demonstrated that the concentration of Ti-ions and corrosion rate (Icorr) are strongly correlated (r = 0.997, p = 0.046). This study indicated that high Ti-ion concentration potentially aggravates corrosion. Under such a severe corrosion environment, there is a potential risk of increased implant associated adverse tissue reactions.

Assessment of wear resistance of hardened additive products made of electroerosive cobalt-chromium powder

Experimental studies of the wear resistance of hardened additive products made of electroerosive cobaltchromium powder obtained in alcohol are carried out. With a friction path of 500 m, the following was established: partial wear of the counterbody and adhesion of wear products of the sample to the counterbody; the size of the wear track of the sample; the depth of the profile of the wear groove of the sample surface; friction coefficient; wear of a counterbody made of steel and a hardened sample made of a cobalt-chromium alloy. Keywords: electroerosive cobalt-chromium powder, additive product, hardening, wear resistance. [email protected]