Diffusion Layer Growth Mechanism in ASPN Method Using an Iron Cage for St52 Steel

Abstract

The mechanism of diffusion layer growth in plasma nitrided coatings applied on a St52 steel using an active screen is investigated. The nitriding was performed at 450, 500 and 550 •C temperature nitriding times of 5, 10 and 15 h, in a gas mixture containing 20 vol. % H2: 80 vol. % N2 and DC-pulsed plasma nitriding unit. The surface, cross section and the thickness of diffusion of specimens was studied in terms of optical and scanning electron microscopy. According to the measurements of diffusion layer thickness, values of Q and Do for nitrogen diffusion in substrate were calculated as 50585 (J/mol) and 4.11×10-10 (m 2 /s), respectively. The variations of hardness depth during nitriding period were determined.

The Role of the Material of Active Screen During the Plasma Nitriding Process

“…Three different types of plasma nitriding exist: DcPn -direct current plasma nitriding, AsPn -active screen plasma nitriding and AsbPn -active screen biased plasma nitriding. The AsPn was developed to avoid the shortcomings (hollow cathode effect, corner effect) of the other method [9][10][11].…”