Resistance of Thin Layers in Abrasion Under High Pressures

Testing of wear resistance of the layers in contact with abrasive SiO2 was done by two procedures: I - in a laboratory according to ASTM G 65-94, and II - in practice on knives of screw (worm) presses used for oil extraction from sunflower seeds. By comparing of mass loss it was estimated that there is poor correlation between results by dry sand/rubber wheel method compared with results obtained from knives. Carburised layers are compared with thin and harder than SiO2 vanadium created by duplex procedure, and boron treated layers, as well as with CrN and multilayer SiC+DLC protective layers applied by PVD procedures. Based on wear marks analysis of all protective layers and based on mass loss between the samples after testing according to both methods, it has been concluded that there is highly emphasised influence of hardness change from the beginning of under layer towards the core. The influence of hardness change from the beginning of the sub-layer towards the core is very important. That is indicated by greater resistance of vanadium, SiC+DLC and carburised knives as compared to CrN and boron treated ones which have a sub-layer with much smaller hardness.