Studying the adhesion strength of plasma powder metal coatings on the surface of graphite

Abstract

Coatings applied onto the surface of specimens made of UHP electrode graphite are studied. Coatings are applied by thermal spraying in two stages: spraying of a sublayer (layer I) of the powder materials being tested; spraying of the main layer of the plasma coating, consisting of a mechanical mixture of fine spherical aluminum (Al) and copper (CuCr1) powders in an equal volume ratio. The adhesion strength between the coating and the graphite surface is studied as dependent on the following factors: sublayer thickness; the type of preliminary surface preparation; the chemical composition of the powder material of the sublayer. It has been found that the highest adhesion strength between the coating and the graphite base is achieved when the sublayer thickness is 80 µm, when a thread with a depth of 1.0 mm is cut on the base surface, and when Al powder is used as a sublayer.