STUDENÝ Zbyněk University of Defense

Spoluautoři KUSMIČ David

The paper is focused on the fatigue strength in material research. The aim was evaluation of influence of plasma nitriding technology to fatigue strength. Plasma nitriding is a thermo chemical procedure based on diffusion of nascent nitrogen into the surface of steels. This diffusion process is based on the solubility of nitrogen in metal matrix and nitrides creation. Especially at the point of initiation fatigue fracture there is examined in more detail the mechanism of fatigue failure components. Area around inclusion is place where usually arise fatigue fracture. The inclusion is subjected to a thorough examination of the impact in terms of the size of inclusions on the tension amplitude and an analysis of the inclusions chemical composition. Based on performed fatigue tests and won results can be submitted, that the plasma nitriding technology has an positive influence to fatigue strength of machine parts. The fatigue tests performed using the Instron R. R. Moore L2568 device established an increase of fatigue life more than 60 %. The initial amplitude of tension 416 MPa (basic material – heat-treated) was increased after plasma nitriding procedure to 665 MPa. Plasma nitriding treatment was realized under standard nitriding atmosphere conditions 1H2:3N2, to promote the formation of Fe4N phase in the compound layer and so-called white layer. Experimental results were summarized and the Wöhler`s (S-N) curves were created.