Defect and Diffusion Forum Vols. 334-335

Abstract: Thermal expansion coefficients of metal sulfides and their alloys are important for technological processes calculations of sulfide processing materials, for example, the crystallization equipment of nickel and copper-nickel converter matte. The synthesized copper and nickel monosulfide, and nickel and copper-nickel matte have been used as the initial samples. Dilatometric analysis was carried out by dilatometer (Linseis L78 RITA). Differences in the values measured are accounted for by the synthesis samples facilities, the coexistence of several non-stoichiometric sulfide phases and interaction during heating. In the temperature 20-500°C range the coefficients of thermal expansion (α) for the sulfides of copper, nickel and their alloys are changed from 10.4 to 20.610-6 1/K. Changes in the value α are accounted for by phase transitions in sulfide samples at their heating. Considering the properties of the phase components are an additive it is shown the thermal expansion coefficient complex sulfide-metal alloys is possible to calculate.

Abstract: Scandia, yttria doped zirconia ((ZrO₂)_0.96 (REO_1.5)_0.04 (RE=Sc³⁺, Y³⁺)) nanoparticles were prepared by the modified sol-gel method. The microstructure of the products was characterized by X-ray diffractometry (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and Raman spectroscopy. Thermal stabillity of SYSZ nanocrystals were also investigated. The SYSZ nanocrystals synthesized with EGM:Zr⁺⁴ mole ratio 4:1, calcined at 700°C, have average diameter of ~20 nm.

Abstract: Laser - cut quality is mainly characterized by a degree of accuracy in shape, size and also by surface layer conditions after cutting associated with surface roughness. An experimental determination of surface tension (or tensor components) of clean metal surfaces is very difficult and there is no direct method for its measurement. Attention was paid to numerical derivation of surface tensions according to the surface topographical features in laser cutting technology. The surface tensions and temperature dependencies of several metallic materials have been determined and confirmed by data obtained from the literature. It was found to be in very good agreement between our results and data from different sources in the literature.

Abstract: Nowadays, plastics have become one of the most demanded materials, replacing the traditional ones such as metals. Therefore, many companies are concerned with the production of plastics, with their distribution and innovation development. Plastics have found utility in a wide range of applications, we use them every day. Measurement of surface roughness of plastic moldings produced by the injection molding process was carried out by a contact profilometer Mitutoyo Surftest SJ401. A reason for this measurement is to obtain information about surface roughness. For further technical adjustment is required to have higher surface roughness what helps to increase electrical conductivity of plastic moldings. This involves determination of a ratio between Ra/Rz (the ratio between the arithmetic average of the roughness profile Ra and the average maximum height of the profile Rz) in order to satisfy customer demand for achieving better surface characteristics leading to an increase in electrical conductivity.

Abstract: Petroleum-based fuel is facing significant depletion issue due to its limited reserves and increasing demand from various industries. Thus, various considerations from economical, environmental and political concerns have motivated researchers to develop alternative energy sources such as biofuel to decrease dependence on petroleum-based fuel. However, the changes in the fuel composition of biofuel affect the material compatibility. In engineering applications where elastomeric components are exposed to hostile environment such as palm biodiesel medium, at least two aspects contribute to the degradation of the materials during the service: diffusion of the liquids leading to swelling and fluctuating multiaxial mechanical loading leading to fatigue failure. Therefore, it is of utmost importance to study the mechanical responses of elastomers under this coupled diffusion-mechanical loading in order to predict accurately their fatigue failure. The present work investigates the swelling of elastomers under simultaneous diffusion of palm biodiesel and multiaxial large deformations.

Abstract: In this work we carried out a numerical study of the heavy oil recovery process in oil reservoir through water injection. We performed transient tridimensional numerical simulations, considering an isothermal process, with a variation in the position of water injection section (interior and surface) in the reservoir, using the ANSYS CFX 11 commercial package and evaluated its effects on the recovery factor of oil. The numerical results showed that varying the flow rate of water injection from 0.10 to 0.25 kg/s there was an increase in the flow of water and oil produced in 193% and 28%, respectively, and the recovery factor in 16.7%

Abstract: In this work, results have been presented related to the influence of selected electrical parameters of the AEDG process on the energy consumption and state of the internal stresses in the outer layer at this stage of the process, in comparison with conventional grinding. The basis of this work has been possible by investigations of the deep grinding of surfaces of the titanium alloy Ti6Al4V with the use of a CBN grinding wheel and sintered carbide S20S with using diamond grinding wheel with metallic binding agent. For the comparative evaluation of the conventional grinding and AEDG, measurements of the specific grinding energy, energy of the spark discharge and internal stresses in the surface layer have been used.

Abstract: X38CrMoV5-1 steel is a typical tool steel commonly used in forging and plastic moulding industry for production of ejectors, slides, dies, etc. In plastics moulding a lot of these parts sustain relative movement. Because of this, some seizing or micro-welding may appear, especially when lubrication is not used. For many years, the different types of protective coatings were developed to avoid such problems. Most of the obtained solutions relate to the manufacturing of low friction coatings obtained by different nitriding processes and by CVD or PVD methods. In this article, the friction coefficients and the wear resistances of TiC+a-C:H protective coatings manufactured on X38CrMoV5-1 steel samples by using PVD technology are studied. The investigations are based on tribometer tests in different temperature conditions. The process of deposition of PVD coatings was realized by using multisource, hybrid factory-scale equipment of type URM 079. This equipment allows for deposition of coatings by a physical method. The tribological tests were performed using a precision high temperature tribometer under ambient and high temperature conditions with a steel and corundum balls as a counter-samples. In this paper, the results of these tribological tests are presented. It is shown that the measured friction coefficient of steel samples with PVD coatings is significantly lower than the friction coefficient of uncoated steel. It is also shown that X38CrMoV5-1 steel samples with manufactured TiC+a-C:H coatings are characterized by a very low friction coefficient and high wear resistance.

Abstract: 440C martensitic stainless steels are widely used because of their good mechanical properties. The mechanical properties of 440C martensitic stainless steel were evaluated after heat treatment of these materials at various types of heat treatment processes. The initial part of this investigation focused on the microstructures of these 440C steels. Microstructure evaluations from the as-received to the as-tempered condition were described. In the as-received condition, the formations of ferrite matrix and carbide particles were observed in this steel. In contrast, the precipitation of M₇C₃ carbides and martensitic structures were present in this steel due to the rapid quenching process from the high temperature condition. After precipitation heat treatment, the Cr-rich M₂₃C₆ carbides were identified within the structures. Moreover, a 30 minutes heat-treated sample shows the highest value of hardness compared to the others holding time. Finally, the tempering process had been carried out to complete the whole heat treatment process in addition to construct the secondary hardening phenomenon. It is believed that this phenomenon influenced the value of hardness of the 440C steel.

Abstract: The benefits of biodiesel to the economy and the environment have motivated increasing interest among researchers to study the feasible utilization of this fuel. The majority of the research focuses on the production of biodiesel and the simple compatibility tests of the engine components with biodiesel. The effect of palm biodiesel diffusion on the mechanical responses of swollen rubber is rarely explored. This paper describes a simple experimental procedure to conduct a stress free diffusion test. Moreover, the mechanical responses are evaluated.