Reduction of wall friction of fine powders by use of wall surface coatings

In this study, the possibilities for the reduction of powder wall friction by different types of surface coatings on the wall material were investigated. Two conventional coatings, an ultra-high molecular weight polyethylene plate and an anti-friction varnish, were tested, together with a diamond-like carbon coating. It is the first time a diamond-like carbon coating has been researched with respect to powder wall friction reduction. The wall friction angles were measured with a ring-shear tester. The results showed that the conventional coatings did not really reduce wall friction in comparison to structural steel. In comparison to the stainless steel they even increased it. In contrast, the diamond-like carbon coating reduced wall friction significantly. These first results are very promising. However, more detailed investigations are required.