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Effect of plasma nitriding process on the fatigue and high temperature corrosion resistance of Inconel 740H nickel alloy

Kopec Mateusz, Gorniewicz Dominika, Kukla Dominik, Barwinska Izabela, Jóźwiak Stanisław, Sitek Ryszard, Kowalewski Zbigniew L.

Archives of Civil and Mechanical Engineering

2022

Vol. 22, no. 1

art. no. e57, 2022

The paper presents a comparison of microhardness, fatigue and high temperature corrosion of Inconel 740H nickel alloy in its as-received state and the same material with nitrided surface layers. The nitrided layers were produced using traditional glow discharge nitriding (specimens nitriding on the cathode potential) and an active screen (specimens nitriding at the plasma potential). A microstructure of the layers was characterized through the scanning electron microscopy, X-ray energy dispersive spectroscopy and X-ray diffraction analysis. Mechanical properties of the nitrided Inconel 740H alloy were examined using microhardness measurements and standard fatigue tests. It was found that Inconel 740H with a nitrided surface exhibited an improved fatigue response of 50 MPa in the whole range of stress amplitudes from 350 to 650 MPa and almost 325% increase of hardness for plasma modified surface and 250% for cathode modified surface. Additionally, the application of cathode nitriding enhanced the corrosion resistance of the alloy in question and effectively protected it against a high temperature oxidation.

Fe-Al based composite reinforced with ultra-fine Al2O3 oxides for high temperature applications

Kopec Mateusz, Jóźwiak Stanisław, Kowalewski Zbigniew

Journal of Theoretical and Applied Mechanics

2021

Vol. 59 nr 3

509--513

In this paper, an Fe-Al based composite reinforced with ultra-fine Al2O3 oxides was obtained through sintering of aluminium, iron and mullite ceramic powders using self-propagated high temperature synthesis (SHS). The powder mixture with a 50%wt. content of the ceramic reinforcement was cold pressed and subsequently subjected to the sintering process in vacuum at 1200◦C for 25 minutes under external loading of 25 kN. The complex microstructure of the Fe-Al matrix reinforced with ultra-fine Al2O3 oxides was found to be desired in high temperature applications since only 3% of the relative weight gain was observed after 100 hours of annealing at 900◦C.