Papers by Keyword: Wear

Abstract: The paper presents the results of experimental research on the wear mechanism of the tool-electrode as a result of machining metal materials by applying electric discharges in pulse. It examines several phenomena noticed on the tool - electrode surface, exactly, the oxide layer formation and the modification of the micro geometry of the tungsten tool electrode surface. The paper presents the experimental results on the behavior of the tool electrode made of stainless steel after the metal parts have been machined. It also presents the phases of mass transfer in the gap between electrodes.

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: It is known that in the cutting processes, due to the parameters variation of the working regimes, to the unevenness of the cutting depth, to the physico-mechanical characteristics of the processed material, to the existence or nonexistence of the coolant oiling, can appear more or less an accentuated wear of the cutting tools. All this factors have a dominant and negative influence on the durability, fact that impose being necessary taking into account some measures to increase the values of the cutting tools and/or of theirs cutting plates durability. In this sense are known various coating by deposition in vacuum researches (vacuum thermal evaporation and condensation from the vapor phase, ionic plating, vapour chemical deposition at low pressure, and so on) of some different filler materials, in thin layers, having protection role for the cutting plates, to increase the edge hardness to the superficial layer and of the tool locating and clearance surfaces and respectively, of their wear resistance. For this purpose, the authors propose to improve cutting tools durability using the deposition method by ionic plating in vacuum (PVD) of the thin titanium layers, following the cutting tools behavior in operation treated in this way. It was so studied the metal carbide cutting plates wear variation, coated with a titanium thin layer and it was determinated the cutting plates durability increasing, in comparison with those untreated. This research is usefull for predicting the lifetime of the cutting tools and/or of theirs cutting plates durability, after the titanium thin layer application, with a significant cost reduction.

Abstract: Wear tester UMT-2 was used to study the friction wear characters of galvanized sheets under dry friction and oil lubrication. Three-dimensional morphology instrument WYKONT11 was used to observe the width and maximum depth of wear scars, surface roughness and surface topography. Energy Dispersive Spectroscopy (EDS) analysis of zinc coating compositions and tests of micro hardness were carried out. Then, the friction wear mechanism of galvanized sheets was preliminary discussed. The experimental results indicate that, under dry friction, galvanized sheets experience three stages: run-in wear, abrasive wear and adhesive wear. Meanwhile, zinc coatings exfoliate until they lose efficacy. Good lubrication is propitious to protect zinc coatings and it can reduce friction wear. The research results can provide guidance for formability analysis and mold design of galvanized sheets.

Abstract: A new polishing method by using fixed soft abrasive film is proposed to polish the end-face of the optic fiber connector. In order to study the wear property of the fixed soft abrasive film, the Particle Flow Code program was employed to simulate the interaction of surface topography. The discrete element model of the optic fiber connector and the fixed soft abrasive film were established. Through the interaction of the surface of two models, the process of contact and friction between the fixed soft abrasive film and the end-face of the optic fiber connector could be simulated. Simulation results showed that the main factors affecting the wear of the fixed soft abrasive film were pressure and speed, which mainly affected the normal stress and the tangential stress respectively. And the wear of the surface was mainly related to pressure and speed. The greater the speed and pressure were, the more serious wear of the fixed soft abrasive film was.

Abstract: Wear characteristics of binder-less (single-phase) nanopolycrystalline diamond (NPD) and cubic boron nitride (BL-PcBN) were investigated by rubbing them against various ceramics such as SiO₂, Si₃N₄, Al₂O₃ and SiC. The wear rates of NPD and BL-PcBN against SiO₂ and Si₃N₄ at high speed rubbing (280-360 m/min) at a loading pressure of 55 MPa (starting condition) were considerably high, indicating the main wear process is a chemical reaction. BL-PcBN specimens were found to be worn at much higher (more than ten times) rates than NPD, suggesting that cBN highly reacts with these ceramics in comparison with diamond under the experiment condition.

Abstract: The surface of the grinding wheel and the conditions under which it is prepared has a profound influence upon the grinding performance as characterised by the grinding forces, power consumption, cutting zone temperature and component surface finish. Only by having a clear understanding of the wheel topography can the interaction of the grinding wheel surface with the workpiece be fully understood. Two dimensional measurements or profilometry, while being a relatively quick measurement to perform, suffers from information quality issues due to the subjectiveness of the profile location as well as questions regarding how representative a profile is of a three-dimensional real surface. While profilometric measurement has long been standardised in the form of various international standards, topographic standards have only recently been agreed upon and formalised as ISO 25178. In this paper a comprehensive approach to wheel topographic characterisation will be undertaken. Factors such as measurement strategy, filtering, active grain identification as well as the fidelity of surface replication will be considered. The paper will propose a recommended measurement strategy and surface parameter set deemed sufficient to provide a comprehensive understanding of the grinding wheel topography.

Abstract: Fixed-abrasive wires, such as electroplated diamond wires and resinoid diamond wires, employed for slicing ingots have the problems of high tool wear. A novel brazed diamond wire has been developed to overcome these problems. This paper investigates the effect of process parameters, including brazing temperature, brazing time and brazing filler composition, on the brazed diamond wire manufacturing with CuSnTi brazing filler. The 3D micro-video system was used to observe the brazed diamond wire surface. Tensile, bending and torsional test were carried out to evaluate the mechanical properties of brazed diamond wire. A brazed diamond wire with 3km length was fabricated with the optimization process parameters, which was successfully used to slice glass.

Abstract: Hot stamping has gained increasing importance in the last years due to the introduction of High Strength Steels (HSS) to improve the strength-to-mass ratio of stamped components. Despite the advantages in terms of load decrease, springback reduction and increased formability, the elevated temperatures the tools are subjected to may determine severe thermal mechanical cycling, increased oxidation and wear, which influence the tools service life and the quality of the produced parts. In addition, the frictional behaviour is also changing with temperature, thus affecting the performance of the forming operation itself. In this paper a novel experimental apparatus suitable for reciprocating sliding wear tests at elevated temperatures is presented. It consists of a linear sliding guideway connected to an electrical actuator and equipped with a heating plate to heat metal sheets. A solid frame embeds a screw device used to apply normal load. Thermocouples placed both on the plate and on sheet sample are used to control temperature during the test. The machine is also equipped with two load cells to record the normal and the tamgential loads. The 22MnB5 high strength steel was chosen as reference material for the machine testing. The results showed the capability of the new equipment and the good stability of the mechanical and thermal condition during testing.

Abstract: Electroless plating technology was applied in order to improve the poor wettability between copper and SiC. β-SiC_(w+p)/Cu composites were fabricated by hot-press sintering. The influences of SiC volume fraction on microstructure, relative density and wear propertity were researched in detail. It turned out that SiC particles and wiskers distributed in Cu matrix homogeneously. And with the increase of SiC volume fraction, the relative density and friction coefficient were reduced respectively, the wear-resistant improved greatly.