Effect of plasma nitriding of austenitic stainless steel produced by direct metal laser sintering

A special additive manufacturing (AM), called as Direct Metal Laser Sintering (DMLS), is a technology that produces 3D workpieces using a wide range of different metals as raw materials. The aim of current research is to investigate the plasma nitriding effect on the DMLS produced samples. The direct current plasma nitriding treatment was achieved at 440 °C for 4 hours with 75%N2 – 25%H2 gas mixture. Before the treatment, the 316L austenitic stainless steels samples were ground with different methods to modify the surface roughness. Scanning electron microscope (SEM), X-ray diffractometer, glow discharge optical electron spectroscopy, Vickers microhardness tester and potentiodynamic corrosion test were used for the characterization of surface properties. The results demonstrated that the surface roughness did not affect the outcome of the plasma nitriding, but the corrosion resistance increases with the decrease of the surface roughness compared to the untreated 3D sample.

Graphene Flakes for Electronic Applications: DC Plasma Jet-Assisted Synthesis

The possibility of graphene synthesis (the bottom-up approach) in plasma and the effective control of the morphology and electrical properties of graphene-based layers were demonstrated. Graphene flakes were grown in a plasma jet generated by a direct current plasma torch with helium and argon as the plasma-forming gases. In the case of argon plasma, the synthesized graphene flakes were relatively thick (2–6 nm) and non-conductive. In helium plasma, for the first time, graphene with a predominance of monolayer flakes and high conductivity was grown in a significant amount using an industrial plasma torch. One-dimensional (1D) flow modeling shows that the helium plasma is a less charged environment providing the formation of thinner graphene flakes with low defect density. These flakes might be used for a water-based suspension of the graphene with PEDOT:PSS (poly(3,4-ethylenedioxythiophene): polystyrene sulfonate) composite to create the structures employing the 2D printing technologies. Good structural quality, low layer resistance, and good mechanical strength combined with the ability to obtain a large amount of the graphene powder, and to control the parameters of the synthesized particles make this material promising for various applications and, above all, for sensors and other devices for flexible electronics and the Internet of things ecosystem.

Thermal And Chemical Resistance Of Plasma Sprayed Al2o3, Al2o3-Tio2 Coatings

In this article, the results of thermal and chemical resistance, of plasma sprayed Al2O3 and Al2O3-13wt.TiO2 coatings on a steel (P265GH) sample are presented. Coatings were formed using air-hydrogen plasma direct current plasma torch at atmospheric pressure. The resistance of coatings was measured by analyzing surface structure, elemental and phase composition of as sprayed coatings and after several heating cycles, imitating application conditions. To make this technology more appealing, by decreasing exploitation cost of standard cast iron grate used in straw pellet broilers, we used cheaper stainless steel with a protective Al2O3 and Al2O3-13wt.% TiO2 coatings. Most of the research done in this field is by using Ar as primary gas, but to decrease the manufacturing cost even further we used Air as primary gas. It was determined that after heat treatment the minor changes in the elemental composition were observed. Meanwhile an additional crystalline phases of metal oxides were detected.

Thermal And Chemical Resistance Of Plasma Sprayed Al2o3, Al2o3-Tio2 Coatings

In this article, the results of thermal and chemical resistance, of plasma sprayed Al2O3 and Al2O3-13wt.TiO2 coatings on a steel (P265GH) sample are presented. Coatings were formed using air-hydrogen plasma direct current plasma torch at atmospheric pressure. The resistance of coatings was measured by analyzing surface structure, elemental and phase composition of as sprayed coatings and after several heating cycles, imitating application conditions. To make this technology more appealing, by decreasing exploitation cost of standard cast iron grate used in straw pellet broilers, we used cheaper stainless steel with a protective Al2O3 and Al2O3-13wt.% TiO2 coatings. Most of the research done in this field is by using Ar as primary gas, but to decrease the manufacturing cost even further we used Air as primary gas. It was determined that after heat treatment the minor changes in the elemental composition were observed. Meanwhile an additional crystalline phases of metal oxides were detected.