MATERIALS ENGINEERING, Vol. 17, 2010, No. 1
published on April 2010

CONTENTS and ABSTRACTS

Jurči, P. (pp. 1-10)
STRUCTURAL CHANGES IN Cr-V LEDEBURITIC STEEL DURING AUSTENITIZING AND QUENCHING Full text (PDF 6649 kB)
The Vanadis 6 PM Cr-V ledeburitic steel was austenitized at temperatures from the range 1000 – 1200 oC and nitrogen gas quenched. Structural changes were investigated by light microscopy and SEM. Obtained result fixed that the M7C3-carbides underwent a complete dissolution in the austenite while MC-phase remained almost completely unaffected. The saturation of the austenite by chromium and partly vanadium induced formation of increased portion of non-martensitic structural components after quenching, due to decrease of MS and Mf temperatures. Undissolved part of MC-carbides, located mainly on the grain boundaries, hinders effectively the grains coarsening also at higher austenitizing temperatures.

Iždinská, Z., Nasher, A., Iždinský, K. (pp. 11-16)
THE STRUCTURE AND MECHANICAL PROPERTIES OF NiCrBSi COATINGS PREPARED BY LASER BEAM CLADDING Full text (PDF 1195 kB)
In this work, the influence of processing conditions on the microstructure and abrasive wear behavior of a NiCrBSi laser clad coating is analyzed. The powder was applied onto a mild steel substrate (Fe–0.17% C) by different laser powers and cladding speeds providing 0.7 – 1.2 mm thick coatings. The microstructure of coatings was analyzed by scanning electron microscopy (SEM). Energy-dispersive X-ray spectroscopy (EDX) was applied for chemical analysis and tribological properties of coatings were evaluated by pin-on-disc wear test. EDX analysis reveals the influence of cladding speed on dilution of iron from the substrate into the coating. Higher iron content matches with lower hardness and wear resistance of appropriate coatings. Obtained results indicate that laser cladding is suitable technique for manufacturing NiCrBSi abrasive wear coatings and that it is possible to find out proper parameters in order to optimize tribological behavior of these coatings.

Koleňák, R., Augustín, R., Ruža, V., Nerádová, M.(pp. 17-22)
THE INFLUENCE OF HIGH-TEMPERATURE BRAZING UPON INDICATORS OF MATERIAL BRAZEABILITY Full text (PDF 847 kB)
The effect of both common and extreme parameters of AISI 321stainless steel high-temperature brazing using the NI 102 brazing alloy upon material brazeability indicators. The ascertainment of the wetting angle, the area over which Ni brazing alloy spreads, the width of AISI 321 steel's dissolubility band, and the width of Ni brazing alloy’s diffusion band into the basic material.

Rodziňák, D., Jakubédzyová, D., Zahradníček, V., Hvizdoš, P.(pp. 23-28)
ROLLING CONTACT FATIGUE AND WEAR OF CrL AND CrM MODE POWDER METALLURGY STEELS Full text (PDF 836 kB)
Contact fatigue properties of sintered steels type CrM and CrL with addition of 0,3-0,7 %C were examined on the device type „pin on disc“ and confronted with wear tests on the same principle. Achieved outcomes are better for CrM material; the higher carbon content the better they are. Fatigue strength ranges from 925 - 1410 MPa and is consistent with the value of hardness. Dry wear tests show that the wear is dependent on the hardness of carbide particles (microhardness) and not on macrohardness of material. These causes wear of indentor. Between values obtained from tests of contact fatigue and wear testing is not possible to find relevant compliance. Both rupture mechanisms are based on breaches of other principles, particularly the PM materials are in the mode of wear that is not sufficiently explored.

Peľák, S., Kocúrová, K., Hazlinger, M.: (pp. 29-33)
CRACK REASON ANALYSIS OF DAMAGED CARBONITRIDED PART Full text (PDF 1464 kB)
The article deals with the analysis of a damaged part, which was designed for use in a mechanical clutch of a car. The crack in the part was found during the production inspection. The aim of metallographic and fractography analyses of the fracture surfaces was to discover the reasons for the crack. The reason for creating the crack was the formation of smaller cracks in the production during pressing process of the semiproduct. These cracks even grew after the following thermochemical treatment. The fracture was initiated during the straightening process of quenched part.


© University of Žilina, Faculty of Mechanical Engineering, ISSN 1335-0803