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Hrubovcakova M.,Ustav materialoveho vyskumu SAV | Dudrova E.,Ustav materialoveho vyskumu SAV
Chemicke Listy | Year: 2011

The contribution deals with the effect of sintering temperature (1120 and 1200 oC) and atmosphere type (N2 and N2+10 % H2) on oxide reduction during the sintering of the Astaloy CrM+0,5 % C. Continuous monitoring of the output atmosphere composition showed that at temperatures above 750 °C carbothermic reactions start and at temperatures above 900 °C increases the CO content with maximum at 1120 °C, which corresponds to reduction of surface Cr oxides and Fe inner oxides. At a temperature of ~1200 °C maximum reduction of stable inner oxides was identified. Sintering at 1200 °C results in reduction of O2 content by 90 %; C content decreases from 0.5 % to 0.34-0.37 % which results in the values of the fracture strength of 945 MPa.

Jakubeczyova D.,Ustav materialoveho vyskumu SAV | Hvizdos P.,Ustav materialoveho vyskumu SAV | Hagarova M.,Ustav materialoveho vyskumu SAV | Dzupon M.,Technical University of Kosice
Chemicke Listy | Year: 2011

VD techniques (ARC and LARC) were used for de ositon of thin coatings - AlTiCrN and nc-AlTiN/Si3N4) onto cutting tools made by owder metallurgy. The coatings were analyzed by standard techniques for surface status and quality assessment. Testing of the service lifetime of the cutting tools was carried out according to the standard ISO 3685- 1999. The results showed two to three times longer lifetimes of the cutting tools in com arison with equivalent uncoated M and traditional material.

Falat L.,Ustav materialoveho vyskumu SAV | Kepic J.,Ustav materialoveho vyskumu SAV | Vyrostkova A.,Ustav materialoveho vyskumu SAV | Svoboda M.,Ustav fyziky materialu AVCR | Brziak P.,Vyskumny ustav zvaracsky PI SR
Chemicke Listy | Year: 2011

In this study the microstructure and creep characteristics of similar ferritic/ferritic and dissimilar ferritic/austenitic weld joints have been investigated. In the case of similar T92+T92 weld joints the T92-based filler metal was used, whereas the dissimilar T92+TP316H weldments were prepared using the Ni-based welding consumable Nirod 600. All weldments were fractured in their ferritic part by the "type IV cracking"failure mode. The similar welds exhibited lower creep life and higher reduction in area than the dissimilar ones. These differences may be related to the different welding conditions of the similar and dissimilar welds as well as their different creep deformation characteristics influencing the final creep fracture behaviour.

Sopcak T.,Ustav materialoveho vyskumu SAV | Bures R.,Ustav materialoveho vyskumu SAV | Streckova M.,Ustav materialoveho vyskumu SAV | Faberova M.,Ustav materialoveho vyskumu SAV
Chemicke Listy | Year: 2011

Different phenol-formaldehyde resins of resol type have been synthesized by the use of various fenol/formaldehyde ratios and different catalysts. The composition of resol-type prepoymer has been optimized for preparation of soft magnetic composite. Mechanical and physical-chemical properties of prepared powder composite material have been improved by prolonged curring schedule. The distribution of resin prepolymer between Fe powder particles has been analysed by employing optical and scanning electron microscopy. The composite material composed of phenol formaldehyde resin and iron powder particles exhibits the higher hardness after the preparation without addition of ethylenglycol.

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