Filters

2020 - 20212

More filters

20232
Reset filters

Settings

Author: van Helden, Jean-Pierre H. × Subject: Plasma nitrocarburizing ×

Search Results

Now showing 1 - 2 of 2
  • Thumbnail Image
    Item
    Solid carbon active screen plasma nitrocarburizing of AISI 316L stainless steel in cold wall reactor: influence of plasma conditions
    (Rio de Janeiro : Elsevier, 2020) Jafarpour, Saeed M.; Puth, Alexander; Dalke, Anke; Böcker, Jan; Pipa, AndreiV.; Röpcke, Jürgen; van Helden, Jean-Pierre H.; Biermann, Horst
    Low temperature plasma nitrocarburizing processes are widely used surface treatment techniques to improve the surface hardness and wear resistance of stainless steels without loss of their excellent corrosion resistance. In the present study, plasma nitrocarburizing based on the active screen technology was applied in an industrial-scale cold wall reactor for the treatment of AISI 316L. Different technological aspects of a cold wall active screen plasma nitrocarburizing (ASPNC) reactor are addressed. The current study compiles recent achievements for the ASPNC treatment using an active screen made of carbon fibre-reinforced carbon under varying plasma conditions. In addition, it is shown that utilizing an active screen made of carbon opens up the possibility to control the structural properties of expanded austenite by the variation of the plasma conditions. It is revealed that for the ASPNC treatment using an active carbon screen, the high reactivity of the generated plasma at the carbon surface suppresses the requirement to apply a bias discharge.
  • Thumbnail Image
    Item
    Influence of oxygen admixture on plasma nitrocarburizing process and monitoring of an active screen plasma treatment
    (Basel : MDPI, 2021) Böcker, Jan; Dalke, Anke; Puth, Alexander; Schimpf, Christian; Röpcke, Jürgen; van Helden, Jean-Pierre H.; Biermann, Horst
    The effect of a controlled oxygen admixture to a plasma nitrocarburizing process using active screen technology and an active screen made of carbon was investigated to control the carburizing potential within the plasma-assisted process. Laser absorption spectroscopy was used to determine the resulting process gas composition at different levels of oxygen admixture using O2 and CO2, respectively, as well as the long-term trends of the concentration of major reaction products over the duration of a material treatment of ARMCO® iron. The short-term studies of the resulting process gas composition, as a function of oxygen addition to the process feed gases N2 and H2, showed that a stepwise increase in oxygen addition led to the formation of oxygen-containing species, such as CO, CO2, and H2 O, and to a significant decrease in the concentrations of hydrocarbons and HCN. Despite increased oxygen concentration within the process gas, no oxygen enrichment was observed in the compound layer of ARMCO® iron; however, the diffusion depth of nitrogen and carbon increased significantly. Increasing the local nitrogen concentration changed the stoichiometry of the ε-Fe3 (N,C)1+x phase in the compound layer and opens up additional degrees of freedom for improved process control.