Papers by Author: László Kuzsella

Abstract: The physical simulation is an ultimate innovative way to develop the welding processes. The paper introduces the connection between weldability and physical simulation, hot-cracking sensibility, the Gleeble 3500 thermo-mechanical physical simulator, respectively. Four kinds of materials were investigated and different kinds of physical simulation test methods were made such as, identification of the Nil-Strength Temperature (NST), hot tensile tests (on heating and on cooling parts of the welding simulation curve are also investigated). Furthermore, Heat Affected Zone (HAZ) tests are being introduced. The future approaches of the research are also exposed.

Abstract: Silicon nitride-based nanocomposites with different quantities (0, 1, 2 wt%) of multiwall carbon nanotubes (MWCNT) have been prepared by isostatic pressing. Abrasive tribological tests were carried out at room temperature in ambient atmosphere with various types of abrasives (different material and grain size) and lubricants respectively. Worn surfaces were characterized by surface roughness parameters, surface topography and scanning electron microscope while wear rate was featured by the worn mass. Results indicate that increase in MWCNT-content leads to decrease of abrasive wear resistance which is proven by increase of R_a and R_z roughness parameters and SEM-analyses of the abrasive worn surfaces.

Abstract: Pin-on-disc tribological tests were performed on Si3N4/SiC/graphite ceramic composites with 5N applied load, at room temperature in dry conditions. Tests were completed with microhardness tests (F=10N), indentation fracture toughness tests (F=100N), furthermore morphological analyses of the wear tracks by SEM. Based on SEM pictures of the wear traces the main damage mechanism could be identified as an abrasive wear. The purpose of the paper is to model the abrasive wear of the given composites. For this reason lateral crack chipping model suggested by Evans and Marshall for Si3N4 ceramics was used for the assessment of the worn volume of the abrasive wear process. The model has been applied with the aim of validating it

Abstract: The main topic of the current work consists in analysing the tribological behaviour of graphite reinforced Si3N4 nanocomposites. The basic aim was to investigate the influence of microstructural features, i.e. amount and grain size of the added reinforcing graphite, as well as the effect of applied load on the wearing characteristics like wearing profile, wear rate, friction coefficient or mechanism of the wear damage process. Tribological tests were performed on a pinon- disc tribometer with on-line measurement of friction coefficient and the wear profile. Wear tests were completed with traditional micro-hardness and instrumented hardness tests, furthermore fractographical analyses of the wear tracks using scanning electron microscopy.

Abstract: The wood is one of the most favourable structural material. It appears on all fields of the ordinary life. It is difficult to say an application where the wood is not used due to its cheap price, availability and just simply the beauty. Beside of the wide range of process technologies a new process appeared. This process changes the properties of the material and brings many new applications to this traditional material. This process is the compression of the structural wood material. This publication deals with the effect of the compression on the mechanical properties of two hardwoods (beech: fagus sylvatica, oak: quercus) by the help of the three-point bending test and the Charpy impact test.

Abstract: The aim of this research work is to investigate the sliding properties of the monotectic surface layers developed by a laser surface-treatment technology. The coatings-remelting technology has been chosen from the laser surface treatment methods. The surface of Al-Si alloy was coated with a lead layer by galvanizing, then the basic material and the surface layer were remelted together by using laser beam produced a monotectic Al- Pb surface layer. The structure of monotectic surface layer has been determined by means of a light microscope and scanning electron microscope. The sliding properties of the basic material (as cast, nearly eutectic Al-Si alloy), the Al-Si-Pb monotectic surface layer as well as the Al-Cu-Sn sliding bearing (Al-Cu matrix and Sn sliding layer) used in the gas industry have been investigated.

Abstract: Tribological performance of technical ceramics is influenced by various factors. Among the others the material properties, loading conditions, residual stresses as well as chemical reactions and interaction between contacting parts effect the damage process. The current paper focuses on the material features, investigating the possibility of modifying the wearing characteristics of a Si3N4 based technical ceramics by post-heat treatment. The microstructure, the mechanical properties and the wearing characteristics were studied on HIP-sintered SiAlON samples, post heattreated in oxidizing atmosphere at different temperatures. Wearing performance was characterized by pin-on disc tests. The wear rate varied with the temperature of heat treatment. From tribological point of view especially treatment at 1200°C proved to be advantageous Microstructural investigations by TEM and X-ray diffraction studies revealed some explanations of these changes. The above studies were completed by mechanical tests. Microhardness, E-modulus, four point bending strength and indentation fracture toughness have been determined in order to study the correlation between the tribological and mechanical properties. Based on our results, the post heat treatment may be useful to improve the wearing performance of SiAlON ceramics.