|
5330 |
|
Thursday, June 08, 2017, Hall 26 5:00 PM Wear & Corrosion Protection |
|
Wear and corrosion protection and control using tungsten carbide cobalt WC-12Co nano-structured material- technology overview |
|
Naif Alharbi* / Dublin City University, Ireland Ahmed Al Hamed/ Dublin City University, Ireland Khalid Benyounis/ Dublin City University, Ireland Lisa looney/ Dublin City University, Ireland Joseph Stokes/ Dublin City University, Ireland |
|
Serviceable engineering components like turbine blade exposed to complex environments where temperature rises to between 700 and 1200°C or pipes that transfer corrosive chemicals, require surface enhancement to resist such conditions. Such surfaces can be improved by using the correct alloy for coating. For example MCrAlY help retard the effect of oxidation, Zirconium oxide can be used to coat metal casting to protect it from wetting and oxidation and high nickel alloy coating is used on boiler tubing or exhaust fans to protect them from high temperature and chemical corrosion. WC-12Co Tungsten Carbide coatings are well known for their wear resistant properties, by offering an excellent well-bonded coating with very low surface roughness which reduces friction within moveable parts. Recently, new approaches in industry have focused on submicron WC-12Co as a coating material, rather than the conventional microstructure currently used. It has been used either as a substitution to the macrostructure size or as a mix of both (multimodal; mixed micro and nano) powder. This contributes to its superiority compared to conventional materials, which is mostly due to providing a denser coating and a corresponding lower coating porosity (to less than 1%), Plus enhanced mechanical properties, higher hardness and fractural toughness. This is due to the free path reduction between cobalt surrounding smaller WC grains size. However due to the differences in the powder feedstock morphology and the WC grain size, the submicron coating can be more susceptible to decarburization effects, characterized by losing one or all of its carbon gases, due to a higher specific surface and thus makes it more sensitive to high flame temperature, so any benefits gained by reducing the WC grains size have thus been offset by the deleterious effects of carbon diffusion. This work will review the recent published work studied the performance of such conventional and nanostructured WC-12Co Tungsten Carbide materials in the form of coatings deposited by high velocity oxy-fuel HVOF thermal spraying. KEYWORDS: Nanocomposite, HVOF thermal spray, WC-12Co, Ni-Cr Inconel 625 alloy. |