Study of Tribological Characteristics of Compatible Materials in Tribosystems of Extruders for Manufacturing Solid Fuel from Biomass

This paper presents the results of the study of the tribological characteristics of compatible materials, the thickness of the protective films, the depth of scratches, and the roughness of the friction surfaces of specimens in model tribosystems for EV-350 and EV-350-50M extruders for manufacturing solid fuel from biomass. It is found that the addition of an alkaline additive agent, namely, sodium hydroxide, which creates a slightly alkaline medium of pH 7.4, decreases the wear rate and increases the service life of a conveyor and dies of an extruder. It is found that, in a slightly alkaline medium of pH 7.4, the roughness of the working friction surfaces is less than the roughness of surfaces in a slightly acidic medium of pH 5 and a strongly alkaline medium of pH 11. The impact rating of different factors on the wear process is determined, which includes, in descending order, abrasiveness, active acidity of a medium, and load. Considering this rating, the selection of compatible materials for extruder tribosystems that increase their service life is justified; such materials are steel 95Kh18 and cast iron ChKh32. It is established that the use of raw materials that have a slightly alkaline medium close to neutral leads to slight traces of corrosion on the working surfaces caused by the formation of passive films on the metal surface, which slow down the oxygen diffusion to the metal surface and catalytically reduce the corrosion rate.