Advanced Materials Research Vol. 1036

Abstract: In the article are presented investigations of the reflectance and the absorption coefficient of yttrium partially stabilized zirconia (YPSZ), for 10,6μm wavelength electromagnetic radiation as well as for the wavelengths in the range of 0,5-1,1μm. Based on an experimentally obtained absorption coefficients, the amount of laser power densities absorbed within YPSZ was calculated. Also, experimental investigations with Disk laser and CO₂ laser radiation annealing were conducted. It was shown that for different lasers wavelengths and for the same laser beam intensities the microstructural changes in YPSZ are different.

Abstract: The paper aims at studying the phenomenon of adhesion between the graphite pellicles deposited through electric discharges in pulse (EDI) with metal surfaces subjected to processing on the one hand and on the other hand the adhesion of this pellicle with a polyurethane adhesive. Experimental research has shown that, when the surfaces are not treated, the shear occurs in the adhesive, when the test pieces are covered with graphite pellicles the shear occurs on the surface that separates the pellicle from the adhesive. It has been stated experimentally that graphite pellicles deposited through electric discharges in pulse decrease the adhesion between the mating surfaces by at least 40% compared to the not treated surfaces.

Abstract: This paper presents the results of experimental research on Taylor cone shaped menisci formation on the surfaces of pieces by applying electric discharges in pulse. It examines the influence of energy stored in the capacitor and of pulse duration on their formation. The modification of piece surface micro-geometry aims to increase the capacity of absorption of radiation and of particle emission. It shows that the size of formed menisci depends on the energy regime of machining, on the gap size, on the duration of electric discharges in pulse and on thermal physical properties of the material used to execute the piece.

Abstract: In military and mining industry are many machine elements – in our case idlers (for tanks, conveyors, and any others machineries which are using transmissions system which are subjected of coverage with a high wear rezistance powder. These machine elements (idlers) must have high wear proprieties, because the functionality of the entire transmissions systems depends on them. Also the maintenance costs are very high, that is why we proposed to studies how to improve the performances of this machine elements. Researches in surface engineering allow the obtaining of new systems of materials by coating the basic material surface with other material having superior high wear properties. In order to improve the machine elements durability, wear resistance, friction, we proposed to obtain a new system of materials using Atmospheric Plasma Spraying – with Sulzer 9MCE equipment. We have chosen the steel type 34CrNiMo6, MOCN class, STAS 691 - 880 as basic material and we coated it with NiAlSi powder. We made the samples and we tested them. The analysis has been made with Tribometre, which produces some data which link us to a high wear rezistance.The NiAlSi coating deposited on steel substrate is dense and very tought. The results showed that the new material has a better microstructure than the basic material and its physical and mechanical properties have been improved.

Abstract: The paper presents problems of modeling the ship’s hull subjected to the load of shock wave associated with non-contact underwater explosion. The article presents equations for describing the parameters of shock wave subjected to an impulse load. The paper presents a proposal of identification of a degree of hazard the ship’s hull forced from underwater explosion. A theoretical analysis was made of influence of changes of hull structure in vicinity of hull. Modeled signals and hull structure were recognized within sensitive symptoms of three sub models: model of hull structure, model of impact and model of propulsion system. All sub models allow testing forces and their responses in vibration spectrum using SIMULINK software and FEM models. The results of testing allowed performing simulations of a similar nature to the actual loads of underwater explosions. Virtual model of the hull of the ship responds in a similar manner to the real impacts.

Abstract: Implants based on titanium alloys, stainless steel and cobalt –chromium have been the primary biomaterials used for load bearing applications and they have been remarkably successful throughout time, but on the long term, there appear a series of inconveniences regarding these metallic implants. Thus, there have been cases of aseptic osteolysis around the implant, with pain and high degree of loosening of the prosthesis which constitutes a limitation of the long term benefits of metallic implants. Therefore, researchers have found new materials for implants, more competitive and efficient. These are materials that are biocompatible and biodegradable. These constitute a novel class of bioactive biomaterials which are expected to support the healing process of a diseased tissue and to degrade thereafter. Magnesium alloys attracted great attention as a new kind of degradable biomaterial. Mg is an essential mineral for human metabolism and its deficiency has been linked to various pathological conditions. The main advantages of Mg alloys are its superior mechanical and biocorrosive properties and its biocompatibility. Mg is a very light-weight metal with a lower density than that of biocompatible Ti alloys, which is closer to that of the human bone. In the present paper we shall focus on presenting some biological testing studies of several Mg alloys from the system Mg-Ca, with different percentages of Ca. Three methods have been use for this: determining the ph at different sample incubation times in culture environment; citotoxicity tests made in vitro which: evaluate the contact toxicity by putting the samples in the buckets of cellular culture plates; evaluate the cellular proliferation at the surface of the tested materials by fluorescence microscopy and deflection microscopy; evaluation of toxicity by testing the effect of the extraction liquid resulting from the incubation of the material with testing cell specific culture environment.

Abstract: Properties of metallic materials can be improved with special materials depositions. Materials deposited on base materials are qualitatively better than the base materials, with a better hydroabrasive wear and corrosion resistance, also with a chemical attack or mechanical stress improved resistance.The thin layer deposition represents depositions (coatings) with hardening, lubricating, or decorative function, having a thickness of less than 10 micrometers.Such special materials are used in cutting-edge technology, such as nuclear turbines and turbine airplanes, space crafts or submarines, which must withstand high temperature, erosion and different chemical attacks.Along with traditional technologies for obtaining coatings, we assist in the development, improvement and expansion of deposition modern techniques, which ensures high purity and adhesion through a wide variety of processes. These thin layer coated materials should not be very expensive from the economic point of view. That is why, scientists are looking to find out the easiest deposition methods and also with great technical efficiency.In this paper we presented several methods of thin film deposition. We also highlighted some of the advantages and disadvantages of some deposition methods.

Abstract: The need for structural materials in temporary implant applications has grown in the recent years; materials that provide short – term structural support and which can be reabsorbed into the body after healing are being sought. These are materials that are biocompatible and biodegradable. These constitute a novel class of bioactive biomaterials which are expected to support the healing process of a diseased tissue and to degrade thereafter. Magnesium alloys attracted great attention as a new kind of degradable biomaterial. Mg shows great promise as a potential biocompatible and biodegradable material in biomedical applications where it has gained the interest of researchers in the field. Biodegradable and bioabsorbable magnesium – based alloys provide a number of benefits over traditional permanent implants. There are however some disadvantages to the use of Mg alloys, one of the most critical being the release of hydrogen and alkalinization resulted from the corrosion of Mg. In connection to these drawbacks, a possible solution could be finding alloying elements which would contribute to the reduction of the corrosion rate in the human body. Studies show that a promising alloy for Mg, could be Calcium - a major component of the human bone and also an essential element in the chemical composition of cells. The present paper shall focus on the elaboration of Mg-Ca alloys, respectively Mg0,63Ca to Mg0,8 5 Ca, in the form of bars. These bars were obtained by cast in an inert atmosphere in the presence of argon, in order to be analyzed as biodegradable orthopedic implants. The structure of the alloy has been studied through SEM analyses, X-Ray diffraction, and EDAX to determine the chemical composition, as well as the distribution of elements in the structure. The main desiderate is finding an alloy which would have a minimum healing period postsurgery, pathophysiology and toxicology and a promising degradation behavior.

Abstract: In the present study, a high power direct diode laser (HPDDL) was used to deposit composite coatings consisted of Ni-based superalloy Inconel 625 matrix and of WC reinforcement particles with a volume fraction of 60%. The influence of parameters, such as laser power beam (heat input) and WC particles size in the cladding powder on the coatings microstructure and erosion wear properties was investigated. The coatings were examined by optical metallography and scanning electron microscopy. The results showed that direct diode laser cladding provides non-porous coatings with homogeneous distribution of WC particles and very low degree of WC dissolution during cladding process. Erosion resistance of the composite coatings decreases with the size of WC particles decreasing.

Abstract: In military and mining industry are many machine elements – in our case idlers (for tanks, conveyors, and any others machineries which are using transmissions system which are subjected of coverage with low friction proprieties powder. These machine elements (idlers) must have low friction coeficient, because the functionality of the entire transmissions systems depends on them. Also the maintenance costs are very high, that is why we proposed to studies how to improve the performances of this machine elements. Researches in surface engineering allow the obtaining of new systems of materials by coating the basic material surface with other material having superior friction properties. In order to improve the machine elements durability, wear resistance, friction, we proposed to obtain a new system of materials using Atmospheric Plasma Spraying – with Sulzer 9MCE equipment. We have chosen the steel type 34CrNiMo6, MOCN class, STAS 691 - 880 as basic material and we coated it with Al2O3 powder. We made the samples and we tested them. The analysis has been made with Tribometre, which produces some data which link us to a low friction coeficient. The Al2O3 coating deposited on steel substrate is uniformaly deposited on the based steel, and need to be polished to decrease the friction coeficient. The results showed that the new material has a better microstructure than the basic material and its physical and mechanical properties have been improved.