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Evaluation of Microstructure and Wear Behaviour of Nicrbsi Composite Coating Deposited by Atmospheric Plasma Spray and Plasma Transferred Arc on Steel Substrate

Rashid, Majid | 2022

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  1. Type of Document: M.Sc. Thesis
  2. Language: Farsi
  3. Document No: 55439 (07)
  4. University: Sharif University of Technology
  5. Department: Materials Science and Engineering
  6. Advisor(s): Movahedi, Mojtaba; Kokabi, Amir Hossein
  7. Abstract:
  8. Nowadays, in many industrial applications, protecting surfaces has become necessary. This research attempted to create a coating resistant to the wear of NiCrBSi with the help of the atmospheric plasma spray and the process of plasma Transferred Arc on the substrate of the simple carbon steel. Also, in order to study the effect of compositing on hardness and abrasive properties of the APS coatings, NiCrBSi powder was strengthened with 25 weight percent of Titanium Carbide particles so that the NiCrBSi-25TiC composite coating could also be created. According to the nature of the APS process, the substructure of this coating always has some porosity and layered structure, and the connection of the coating to the substratum is mechanical. As a result, in order to reduce their porosity, improve their adhesion with the substrate, and increase their hardness and abrasive properties, the heat treatment was done on them (APS composite and non-composite covers) in a furnace containing Argon gas at the temperature of 600, 800, and 1000 degrees Celsius for 30 minutes. The substructure coating, the degree of porosity, and the connection method of the coating with the substrate are analyzed with the help of an Optical Microscope and Scanning Electron Microscope equipped with EDS. Also, by doing the X-ray diffraction test on the polished surface, it was found that Nickel solid solution phases, Alloy, and Carbide compounds were formed in APS and PTA coatings. With the help of XRD, some amorphous phase was detected in the APS coats after spraying. In order to study the mechanical properties of coatings Vickers Microhardness test was done linearly and at a distance from the interaction of coatings/substrate into the coating on the cross-section of all the coatings. Furthermore, the Pin on Disc wear Test was done with a force of 15 N and a wear distance of 1000 m to study the abrasive properties on their polished surface. The results showed that creating this coating on the steel substrate to increase the hardness and abrasive properties was successful Because the hardness of the used steel after creating the NiCrBSi coating with APS and PTA processes reached 737 Hv and 664 Hv respectively. This coating could decrease the reduced mass in the effect of the Pin on Disc wear test as much as 49 and 75 percent. Heat treatment after deposition increases their hardness and abrasive properties by reducing porosity and interlayer boundary and creating secondary hard sediments like Carbide, chrome alloys, alloys, and Nickel silicas in APS coatings. Adding TiC particles to the coating also causes 14 percent increase in hardness and 48 percent decrease in the mass lost in the effect of the wear test. In the end, it was determined that the coating created by the APS process, composite with TiC particles and heat treated at the temperature of 800°C, has the best abrasion resistance, which was the goal of this research. Hardness and mass loss in this coating were measured as 925 Hv and 11 mg, respectively. By studying abraded surfaces, smooth and sticky wear was identified as the main reason for these coatings' wear
  9. Keywords:
  10. Hardness ; Heat Treatment ; Wear Resistance ; Transitional Curves ; Arc Plasma ; Nickel-Chromium-Boron-Silicon (NiCrBSi) ; Plasma Transferred Arc ; Atmospheric Plasma Spray ; Titanium Carbide

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