K. Sato, J. Kitamura, Fujimi incorporated, Kakamigahara, Japan; H. Ibe, H. Mizuno, Fujimi Incorporated, Kakamigahara, Gifu, Japan
Thermal sprayed various rolls are widely used in the production processes of paper and iron manufacturing industries, for example, where abrasion, corrosion and erosion resistances are generally required. As for paper manufacturing and corrugating rolls, highly wear resistance are most important property to increase lifetime. Therefore, WC cermet coatings by high velocity oxygen-fuel (HVOF) spraying are gradually applied to these rolls as chrome plating alternatives.Due to necessity of mirror or smooth surface in the rolls, in general, WC cermet coatings by the HVOF with rough surface, normally 4~5 micron in average surface roughness (Ra), must be polished resulting in increasing cost and taking time for production. In order to reduce surface roughness of as-sprayed coatings, using smaller particles is effective. However, wear resistance tends to decrease when using smaller powder. In this study, we have found that the WC/12Co coatings with relatively smoother surface, less than 3 micron in Ra, retaining highly wear resistance can be formed by optimizing the particle and spraying parameters, such as particle distribution, particle size, spray distance and flame condition. We can say that this coating enables us to reduce polishing cost and time.
Summary: As sprayed WC cermet coatings by the HVOF have very rough, normally 4~5 micron in average surface roughness (Ra). This rough surface requires long-term polishing treatment in many indstrial applications that causes cost increase and extension of construction work.
In order to reduce surface roughness, using smaller particles is effective. However, wear resistance tends to decrease when using smaller powder. In this study, we have found that the WC/12Co coatings with relatively smoother surface, less than 3 micron in Ra, retaining highly wear resistance can be formed by optimizing the particle and spraying parameters, such as particle distribution, particle size, spray distance and flame condition.
