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5331 |
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Design of experiment study of the relationship between roughness and laser processing conditions of both blended and singular nano-structured WC-12Co HVOF thermal spraying coating |
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Naif Alharbi* / Dublin City University, Ireland Khalid Benyounis/ Dublin City University, Ireland Lisa Looney/ Dublin City University, Ireland Joseph Stokes/ Dublin City University, Ireland |
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When deposition is required onto a surface whose properties and material characteristics differ from that of the bulk substrate. Thermal spraying as a coating technique has proven itself to be one of the most widely recognized industrial solution technologies in providing superior protective coatings. The entire thermal spray coating process involves three main activities, namely; selection, transportation and accumulation of the material onto the bulk material. It serves to accomplish the following purposes: Wear protection, corrosion protection, surface appearance improvement, and/or to impart insulation characteristics. For the coating material to achieve its primary functions listed above, it must have a number of properties such as excellent bond strength, high micro hardness, a dense coating with low porosity and exhibit smooth surface roughness. A smooth coating surface with low roughness without the need for grinding, is not only for aesthetically pleasing but it has also been proven by numerous published researchers to play a major role in other aspects, such as wear rate, porosity level and fatigue failure. For instance, surface roughness has a significant effect on crack propagation in fatigue failure caused by thermal cycling. In this research, two coating material types have been prepared; firstly, 100% Tungsten carbide cobalt (nano-structured) WC-12Co (InfralloyTM S7412) and second, WC-12Co nanostructured powder mixed with a Nickel Chromium alloy (Diamalloy 1005- Inconel 625) at an optimised weight percentage composition of 75% to 25% respectively. The present study looks at the effect of Laser processing parameters on roughness level. A design of experiment (DOE) software was implemented to analyse the experimental data. The substrates were laser treated with CO2 laser of 10.6mm wavelengths. Different outcomes were achieved by varying the laser processing parameters. The parameters varied were the laser power, scanning speed and focal point position, while the laser beam track was kept constant at 40%. KEYWORDS: HVOF thermal spray, WC-12Co coating, Laser treating, surface roughness. |