|
1263 |
|
Wednesday, June 04, 2008, Room 04 10:00 AM HVOF and Flame Spraying New very hard coatings and modern powder feeding for economic dense coatings against wear and corrosion |
|
HVOF coatings by customized cermet materials for various applications |
|
Junya Kitamura* / Fujimi Incorporated, Japan Hiroaki Mizuno / FUJIMI INCORPORATED, Japan Satoshi Tawada/ FUJIMI INCORPORATED, Japan Isao Aoki/ FUJIMI INCORPORATED, Japan |
|
HVOF sprayed cermet coatings are required in various industrial fields due to their excellent properties, such as wear resistance, corrosion resistance, high hardness, high bonding strength and stability under high temperature. In order to utilize them in the fields, optimization of composition and structure of the coatings are essentially important meaning that both spray powders and spray conditions are key process parameters. In this paper, developed spray powders of cermet materials are introduced for the specific applications, where cavitation erosion, mechanical impact, corrosion by molten alloy and general abrasive wear are major factors that damage the coatings. WC/Co/Cr coating composed of large WC particle shows high resistance against cavitation erosion retaining corrosion resistance under wet condition meaning that the coating can be applied to hydraulic machinery, such as water turbine and radial flow pump. HVOF coatings by WC-Cr3C2-Ni mechanically blended with Ni or NiCr have highly impact resistance clarified by impact tester by falling balls quantitatively. The coatings also have good wear and corrosion resistance. Thus, they can be applied to civil and building construction machineries. Die-casting machines retaining long-term operation to produce machinery components made from aluminum, zinc and magnesium alloys are required in automobiles and electric appliances. Further, dipping rolls with higher corrosion resistance against molten zinc (Zn) and aluminum-zinc (Al-Zn) alloy is one of the key issues in continuous hot-dip galvanizing process at steel manufacture. MoB/CoCr coating is one of the candidates for the applications. Increasing size of WC particle in WC cermet coatings improves abrasive wear resistance against SiC particles clarified by Suga-abrasion test. For slurry erosion and blast erosion, effect of WC particle is different from the abrasion suggesting that major factors affecting the wear resistance within coating properties, such as WC grain size, porosity, hardness and toughness, is different when changing wear mode. |