Partners

Abstract:
A new method of surface modification based on the method of electrospark alloying (ESA) using carburizer containing nitrogen—carbon components for producing coatings is considered. New processes have been proposed that include the step of applying saturating media in the form of paste-like nitrogenous and nitrogenous-carbon components, respectively, onto the surface without waiting for those media to dry, conducting the ESA process with the use of a steel electrode-tool, as well as with a graphite electrode-tool. Before applying the saturating media, an aluminium layer is applied onto the surface with the use of the ESA method at a discharge energy of Wp = 0.13–6.80 J. A saturating medium in the form of a paste was applied to the surfaces of specimens of steel C22 and steel C40. During nitriding, nitrocarburizing and carburization by ESA (CESA) processes, with an increase in the discharge energy (Wp), the thickness, micro hardness and continuity of the “white layer” coatings, as well as the magnitude of the surface roughness, increase due to saturation of the steel surface with nitrogen and/or carbon, high cooling rates, formation of non-equilibrium structures, formation of special phases, etc. In the course of nitriding, nitrocarburizing and CESA processing of steels C22 and C40, preliminary processing with the use of the ESA method by aluminum increases the thickness, microhardness and continuity of the “white layer”, while the roughness changes insignificantly. Analysis of the phase composition indicates that the presence of the aluminum sublayer leads to the formation of the aluminum-containing phases, resulting in a significant increase in the hardness and, in addition, in an increase in the thickness and quality of the surface layers. The proposed methods can be used to strengthen the surface layers of the critical parts and their elements for compressor and pumping equipment

Keywords:
electrospark alloying,coatings,roughness,structure,microhardness,continuity,X-ray diffraction analysis,nitriding,nitrocarburizing,carburization

Abstract:
The numerical model of laser welding is presented. The time dependent set of equations describing heating, melting and solidification is solved using ANSYS-Fluent package and adopted to the problem using the external user-defined functions. The developed model is used for investigation of laser welding of Ir pad with spark plug electrode made of Ni. These spark plugs are key parts of industrial internal combustion engines using biogas as fuel. Problems in welding arise from significant difference of melting points of both metals; moreover, the boiling point of Ni is close to melting point of Ir. Theoretical model of the welding process is a useful and cost lowering tool providing guidance for selection of parameters and reducing significantly number of expensive and time consuming experiments

Keywords:
Nd:YAG laser, iridium, Ir, nickel, Ni, spark plug, laser welding, numerical model, dissimilar metals welding, temperature dependent material properties

Abstract:
There have been considered the coating structure modification after electrospark alloying (ESA) by the Mo-electrode using a paste with carbon nanotubes. It was showed that the regimes and composition of the paste influenced the microstructure, continuity, roughness, and hardness of the coatings. The microstructures after the ESA of the Armco iron were studied. The use of higher discharge energy in ESA leads to an increase in surface roughness, coating thickness, and coating continuity. The use of higher discharge energy during ESA results in an increase in surface roughness, coating thickness, and coating continuity. The microstructures reveal nanoscale phases from 40 to 60 nm, which are evenly distributed in the coatings. The addition of ARKEMA nanotubes increases the hardness to 608 HV. The results of local X-ray diffraction analysis showed that carbon is concentrated on the surface, while molybdenum is distributed homogeneously in the coating. The addition of nanotubes to the paste before ESA improves hardness and continuity. The effect of nanotubes on the structure and properties of coatings is positive.

Keywords:
X-ray diffraction, Nanostructures, Nanotubes

Abstract:
W pracy został przedstawiony model teoretyczny oddziaływania wiązki laserowej z materiałami różnoimiennymi w procesie spawania. W celu wyznaczenia rozkładu pola temperatur, wymiarów spoiny oraz strefy mieszania się materiałów zbudowano trójwymiarowy, niestacjonarny model numeryczny uwzględniający proces wymiany ciepła i masy. Model został wykorzystany do zbadania przebiegu i optymalizacji parametrów procesu spawania niklowo - platynowych nakładek na świece zapłonowe dla silników na biopaliwo. Zbadano pływ czasu trwania impulsu, średnicy plamki oraz kąta nachylenia wiązki na rozkład pola temperatury. Kształt strefy przetopionej otrzymany z modelu teoretycznego jest w dobrej zgodności z wynikami eksperymentalnymi

Abstract:
The paper analyzes the works devoted to solving problems affecting the bearing life of rolling bearings (RB) and to revealing reserves for its increase. There proposed a new technology for forming a protective coating on the shaft bearing journal or on the surface of a sleeve pressed thereon, which consists in the use of a combined technology comprising a process for stage-by-stage aluminizing by the method of electrospark alloying (A ESA ) followed by a process of ion nitriding (IN). Such a coating has a 100% continuity, the greatest thickness of the increased hardness zone of 300 µm, the surface microhardness of 7700 MPa, and the roughness (Ra) after non-abrasive ultrasonic finishing (NAUF) of 0.5 µm, The results of the X-ray microanalysis indicate that an increased content of aluminum is observed in the surface layer at the distance of up to 40 µm after the stage-by-stage AESA process. The research results have shown that in order to restore the shaft bearing journal neck surface layer hardness, which had been lost because of the repair work, the step-by-step AESA technology is more preferable. Thus, when removing the surface layer to a depth of 0.15 mm and subsequently carburizing by the method of electrospark alloying (C ESA ), the maximum microhardness of the surface layer is 7250 MPa, and the thickness of the zone of the increased hardness is 150 µm, At subsequently processing by the AESA method, these quality parameters of the surface layer are, respectively, 7350 MPa and 210 µm. The use of the NAUF method, both after C ESA and AESA processes, makes it possible to reduce the surface roughness up to Ra = 0.5 µm. To decrease the surface roughness of the RB housing seat, it is advisably to practice burnishing with a diamond tool (DB) after the A ESA process

Abstract:
The interaction of laser beam with dissimilar metals during welding process was studied theoretically. A finite element based three-dimensional transient heat transfer and fluid flow model was applied for prediction temperature distribution and material mixing field as well as weld dimensions. The model was used for study and optimization process parameters of welding of Ni – Pt spark plug for bio-fuel engine. The laser pulse duration and energy, and the angle of incidence of the laser beam to thesurface were analyzed. The shape of the melting pool obtained from the theoretical model was close to experimental results.