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No. 2/2019
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Contents


Tadeusz KUBASZEK
Marek GÓRAL
Radosław RÓŻAŃSKI
Łukasz SZCZEPAŃSKI

R&D Laboratory for Aerospace Materials, Rzeszów University of Technology

INFLUENCE OF PLASMA SPRAYING CONDITIONS ON THE MICROSTRUCTURE AND FUNCTIONAL PROPERTIES OF WC-Cr-Ni METALOCERAMIC LAYERS

The article presents the results of research on the impact of the conditions of plasma spraying on thickness and porosity, as well as the erosion resistance of WC-Cr-Ni metaloceramic coatings. It was shown that the selection of current intensity – 450 A and flow rate H2 = 5 dm3/min and Ar = 68 dm3/min allows obtaining a coating with a thickness of approx. 177 μm and low porosity <6%. At the same time, this coating is characterised by the greatest hardness – 758 HV0.5, and the best erosion resistance at room and elevated temperature. The analysis of test results indicates that lower current and hydrogen content in the plasma stream do not ensure sufficient melting of the metallic matrix of the powder – Ni and Cr, and thus greater brittleness of the coating and its lower erosion resistance. It was also found that an increase in plasma stream energy due to an increase in torch current or hydrogen flow rate may cause tungsten carbide to decompose in the plasma stream – the phase affecting hardness and abrasion resistance.

Keywords: plasma spraying, metaloceramic coatings, carbide coatings


Milena KIERAT

Silesian University of Technology, Faculty of Materials Engineering and Metallurgy, Institute of Materials Science

Adam ZIELIŃSKI

Łukasiewicz Research Network – Institute for Ferrous Metallurgy

INCREASED TEMPERATURE AND LONG-TERM IMPACT OF THE AGEING PROCESS ON CHANGES IN THE MICROSTRUCTURE OF THE HR6W ALLOY

The study was carried out to determine the effect of long-term ageing (1,000 and 10,000 hours) at 700°C and 750°C on the microstructure of the HR6W alloy. The study indicates that the long-term effect of high temperature causes significant changes in the microstructure of the examined alloy:

  • After ageing for 1,000 hours at 700°C, in addition to primary MX and M23C6 precipitations, an increase in the size and number of precipitates was observed both inside and along austenite grain boundaries, and the occurrence of the Laves phase was also observed.
  • After 10,000 hours at 700°C, a significant increase in M23C6 precipitates was observed, especially inside and along grain boundaries. An increase in the Laves phase in the microstructure was also observed.
  • The effect of the increase in the ageing temperature to 750°C:
  • It significantly accelerated the precipitation process after just 1,000 hours.
  • In addition to a network of M23C6 precipitates along austenite grain boundaries, their coagulation and an increase in the size of the Laves phase precipitates inside the austenite grains was observed.
  • The extension of the ageing time to 10,000 hours at 750°C contributed to a significant increase in the size of Laves phase precipitates inside austenite grains.

Keywords: HR6W, microstructure, ageing, precipitates


Jarosław MARCISZ
Bogdan GARBARZ
Bartłomiej WALNIK

Łukasiewicz Research Network – Institute for Ferrous Metallurgy

CORRELATION OF MECHANICAL PROPERTIES AND RESISTANCE TO PERFORATION OF ARMOUR ELEMENTS MADE OF NANOSTRUCTURED BAINITIC STEEL

The aim of the paper is to determine the correlation between mechanical properties determined in quasi-static tensile tests and dynamic compression tests, and resistance to perforation and cracking in firing tests of nanostructured bainitic steel sheets. The relationship between mechanical characteristics and ballistic resistance makes it possible to specify and optimise the production parameters of steel elements for armour and shields providing ballistic protection. As a result of the tests, the level of mechanical parameters and the type of microstructure, as well as the minimum thickness of the nanostructured bainitic steel sheet, ensuring compliance with the requirements of level 2 ballistic protection according to Stanag 4569, were determined.

Keywords: nanostructured bainitic steel, dynamic deformation, mechanical properties, microstructure, ballistic resistance


RESEARCH PROJECTS FUNDED FROM THE INSTITUTE’S OWN FUNDS – ABSTRACTS

2019-11-21


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