For the 304 stainless steel and Q235 low-carbon steel electrodes, the samples were polished with 20 mesh brown corundum and ultrasonically cleaned in acetone for 15 min. To remove the grease and avoid any damage on the Fe-Al-Cr coatings, the prepared Fe-Al-Cr coating electrodes were only ultrasonically cleaned in acetone for 15 min, without polishing. Firstly, the samples were embedded in epoxy resin, to prepare the working electrodes, and a Pt foil was used as the counter electrode, and a saturated calomel electrode was used as the reference electrode. Source ElectrodeĮlectrochemical tests were applied to investigate the corrosion resistance of Fe-Al-Cr coatings, 304 stainless steel (chemical composition: Cr: 18.529 wt.%, Ni: 8.545 wt.%, Mn: 1.309 wt.%, Si: 0.331 wt.%, Cu: 0.303 wt.%, C: 0.063 wt.%, P: 0.036 wt.%, S: 0.025 wt.%, and Fe: the balance), and Q235 low carbon steel. The new findings demonstrated in this work provide useful information for the fabrication of high-quality Fe-Al-Cr coatings with excellent corrosion resistance. It was found that Fe-Al-Cr coatings obtained under optimized conditions exhibit excellent corrosion resistance in a 0.5 mol/L H 2SO 4 solution, which is even better than that of the 304 stainless steel. Herein, we focused on the influence of the sample temperature, gas pressure, and electrode distance on the microstructure, morphology, and quality of the obtained Fe-Al-Cr coating deposited on Q235 steel substrates. However, this kind of study is still lacking. A deep understanding of the effects of these parameters on the quality of the obtained Fe-Al-Cr coating is very important to control the mechanical and chemical properties of the coating. ĭuring the processing of DGPSM, the chemical composition and the thickness of the coating are closely related to the plasma temperature, the gas pressure, and the electrode distance (i.e., distance between the substrate and the source electrode). Similarly, Nb was incorporated into Fe-Al coatings to form Fe-Al-Nb coatings by a DGPSM process, which showed improved mechanical properties. For example, Al 2O 3-particles-reinforced Fe-Al coatings were prepared on the surface of 316 L stainless steel by a DGPSM technology and exhibited enhanced wear resistance and corrosion resistance. DGPSM has been regarded as an advanced surface technology for the deposition of high-quality coatings. Then, the glow discharge phenomenon appears, which transfers the alloying elements from the source electrode to the substrate at the cathode, and it can also activate the surface of the substrate to promote the diffusion of the deposited elements to form a diffusion layer. When high voltages are applied between the anode and the cathode, and the anode and the source electrode, the Ar gas is ionized and becomes plasma. Fe-Al-Cr wires forming a mesh structure are used as the source electrode ( Figure 1b). A device to measure atmospheric pressure, the barometer, was invented in 1643 by an Italian scientist named Evangelista Torricelli (1608 - 1647) who had been a student of Galileo.The operating principle of double glow plasma surface metallurgy (DGPSM) technology is schematically illustrated in Figure 1a, where the anode, the cathode, and the source electrode are placed in a container filled with inert gas (Ar). Fortunately, people also have air inside them to balance the force. An average sized person probably has a total force exerted on them from the atmosphere in excess of 25,000 pounds. People, of course also have atmospheric pressure pressing on them. As the water vapor condenses to liquid water, the air pressure outside the can slowly crushes the can flat. As the can cools, the water vapor inside condenses back to liquid water leaving the inside of the an with a lack of air molecules. The lid is then tightly sealed on the can. The water inside the can vaporizes and expands to fill the can, pushing the air out. The can has a few drops of water placed inside and is then heated to boiling. A common demonstration of air pressure makes use of a one-gallon metal can. The pressure exerted by our atmosphere will become quickly noticed, however, if the air is removed or reduced inside an object. This pressure is unnoticed, because the air is not only outside the surfaces but also inside allowing the atmospheric air pressure to be balanced.
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