CONTENTS & ABSTRACTS
In English. Summaries in Estonian
Proceedings of theEstonian Academy of Sciences.
Engineering
Volume 9 No. 4December 2003
Special issue onengineering materials and tribology
BALTMATTRIB-2003
Foreword; 245
Jakob Kübarsepp and Priit Kulu
Evaluationof deformation methods of Cu-Al2O3 systems with qualityfactor; 246–251
Michal Besterci, KatarínaSülleiová, and Priit Kulu
Abstract. Quality of Cu-Al2O3 composite materials,prepared vith powder metallurgy, is assessed on the basis of the analysis ofthe deformation processes. Powder mixture was prepared by grinding Cu and Al2O3particles. After the compaction, the materials were deformed by extrusion,forging, and isostacic pressing. Their microstructure and mechanical propertieswere qualitatively evaluated. By comparison of these three deformationtechnologies we found isotropic microstructure in the materials forged andisostatically pressed. The materials, deformed by hot isostatic pressing, whichpossessed a low residual porosity (< 1%),showed optimum properties (the ultimate tensile strength and reduction of thearea).
Key words: Cu-Al2O3 composites, powder metallurgy,deformation process, mechanical properties, microstructure, quality factor.
Plasticflow of BCC metals at monotonous static and dynamic cyclic loading; 252–260
Antanas Ciuplys, Jonas Vilys, VytautasCiuplys, and Valdas Kvedaras
Abstract. This paper deals with the relation between the physical yieldplateau and multicycle fatigue disintegration peculiarities. Low carbon steel20 yield plateau alteration kinetics during the cyclic loading has beeninvestigated. For this purpose samples were loaded cyclically by a fixed loadfor a number of cycles and after that abruptly statically stretched. It wasestablished that plastic flow of BCC metals on the surface takes placesimilarly during the monotonous static and dynamic cyclic loading.
Key words: metals, mechanical properties, surface layer, cyclic loading,physical fatigue limit, yield plateau.
Elevated temperature wear of chromium carbidebased cermets; 261–271
Irina Hussainova and Maksim Antonov
Abstract. Good thermomechanical properties, combined with low density and bulkchemical stability at temperatures approaching 1300 °C,make chromium carbide based composites of interest for a variety ofwear-resistant applications and especially for applications at elevatedtemperatures. The purpose of this work is to study the erosion behaviour of Cr3C2-Nicermets at room and elevated temperatures of 300 and 600 °C. Systematic studies of the influence of the impact variables onthe collision process have been carried out using silica particles. The erosionof ceramic-metal composites is associated with the combination of ductile andbrittle modes of wear and material behaviour is influenced by bothmicrostructure and test conditions. The high temperature oxidation behaviour ofCr3C2-Ni has been investigated to show the advantage ofthese materials over conventional cemented carbides at elevated temperatures.
Key words: erosion, composites, microstructure, high temperature wear,oxidation.
Durabilityof advanced TiC-base cermets; 272–280
Heinrich Klaasen, JakobKübarsepp, and Irina Preis
Abstract. Mechanical and wear behaviour of some advanced cementedcarbides, prospective for metalforming, TiC-base cermets and WC-base hardmetalsdiffering in composition and binder structure have been analysed in a set oftests including durability (blanking performance and fatigue endurance)complemented by SEM. It was found that the blanking performance (durabilityduring blanking of sheet metals) of a cemented carbide is controlled by itsadhesive wear resistance and fatigue sensitivity (slope of the Wöhler curve).In respect to blanking performance and fatigue endurance, the advantage ofadvanced steel-bonded TiC-base cermet over the conventional WC-base hardmetalused in metalforming has been revealed.
Key words: cemented carbide, cermet, hardmetal, blanking die, fatigue,wear.
Determination of residual stresses in agalvanic coating; 281–292
Alexander Ryabchikov, Harri Lille, and JakubKõo
Abstract. A method for the determination of residual stresses in agalvanic coating by measuring the longitudinal deformation of a straight strip(ribbon) substrate was elaborated. For this purpose, an experimental measuringsystem was designed. Experiments were carried out using a nickel coatingdeposited bilaterally from Watt’s electrolyte on a copper or brass stripsubstrate, and residual stresses were calculated. An equipment for fixing thestrip substrate at one end and a load with a calibrated weight at the other wasdesigned. The longitudinal displacement of the free end of the substrate,depending on the coating thickness, was determined by measuring the deformationof the elastic element. The effect of the rigidity of the elastic element onresidual stresses was investigated. The results are compared with theliterature data.
Key words: residual stress, strip substrate, elastic element,longitudinal deformation, galvanic coating, measuring system.
Sprayparameter optimization and tribological properties of thermally sprayedquasicrystalline and partially quasicrystalline coatings;293–303
Erja Turunen, TommiVaris, Kari Vierimaa, and Simo-Pekka Hannula
Abstract. Good tribological properties and low coefficient of frictionhave previously been reported for thermally sprayed quasicrystalline coatings.In this paper HVOF spray parameter optimization and tribological properties ofquasicrystalline coatings, manufactured from three different compositions, isdiscussed. On-line diagnostics measurements and splat studies were performed tooptimize spray parameters of HVOF. Quasicrystalline coatings were produced andthe coating microstructure was analysed. Large amount of wear and frictiontests were performed to determine the tribological properties ofquasicrystalline coating. Relatively high values of the coefficient of frictionwere obtained in the PoD-test. These tests yielded friction values varyingtypically between 0.4–0.6 independent of the counter material.
Key words: high velocityoxy-fuel (HVOF) spraying, quasicrystalline coatings, friction, wear,microstructure.
Applicationsof recycled hardmetal powder; 304–316
Sergei Zimakov, Toomas Pihl, Priit Kulu,Maksim Antonov, and Valdek Mikli
Abstract. This paper is devoted to the study ofhardmetal powders of different particle shape, produced from used hardmetal bya mechanical disintegrator milling technology. The WC-15Co hardmetal powder of0.2 to 0.5 mm with angular and round particle shape has been investigated.Particle granularity is characterized by the mean particle size and theangularity of milled powders is described by the so-called “spike parameter”.The influence of the hardmetal particle angularity on the erosion rate ofdifferent metallic materials has been determined. The experiments showed thatthis parameter is crucial in abrasive particle shape characterization. The wearresistance of composite coatings, based on self-fluxing alloy and hardmetalpowders of different particle shape, was studied. These coatings showed minimaldifference in their wear resistance.
Key words: hardmetal powder, angularity, abrasivity,powder coatings, wear resistance.
Instructions to authors; 317–319
Copyright Transfer Agreement; 320
Contents of volume 9; 321–322
