Effects of Plasma-Chemical Composition on AISI 316L Surface Modification by Active Screen Nitrocarburizing Using Gaseous and Solid Carbon Precursors

Low-temperature plasma nitrocarburizing treatments are applied to improve the surface properties of austenitic stainless steels by forming an expanded austenite layer without impairing the excellent corrosion resistance of the steel. Here, low-temperature active screen plasma nitrocarburizing (ASPNC) was investigated in an industrial-scale cold-wall reactor to compare the effects of two active screen materials: (i) a steel active screen with the addition of methane as a gaseous carbon-containing precursor and (ii) an active screen made of carbon-fibre-reinforced carbon (CFC) as a solid carbon precursor. By using both active screen materials, ASPNC treatments at variable plasma conditions were conducted using AISI 316L. Moreover, insight into the plasma-chemical composition of the H2-N2 plasma for both active screen materials was gained by laser absorption spectroscopy (LAS) combined with optical emission spectroscopy (OES). It was found that, in the case of a CFC active screen in a biased condition, the thickness of the nitrogen-expanded austenite layer increased, while the thickness of the carbon-expanded austenite layer decreased compared to the non-biased condition, in which the nitrogen- and carbon-expanded austenite layers had comparable thicknesses. Furthermore, the crucial role of biasing the workload to produce a thick and homogeneous expanded austenite layer by using a steel active screen was validated

Solid carbon active screen plasma nitrocarburizing of AISI 316L stainless steel in cold wall reactor: influence of plasma conditions

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

New Iranian and Australian peach latent mosaic viroid variants and evidence for rapid sequence evolution

Peach latent mosaic viroid isolates from peach and plum in Iran have been compared with an Australian isolate from nectarine. Thirteen sequence variants 336-338 nt in size were obtained. All variants clustered phylogenetically with variants reported from several hosts and countries. A total nucleic acid extract, a slightly longer than full-length RT-PCR amplicon, and a recombinant plasmid clone from the Australian isolate were all infectious to, and symptomatic in, mechanically inoculated peach seedlings. The infectious clone generated two progeny viroid molecules, which each showed 10 different mutations compared with the parent clone inoculated 30 days previously.Arezou Yazarlou, Behrooz Jafarpour, Saeed Tarighi, Nuredin Habili and John W. Randle