Abrasion resistance of surface layers

A number of surface layers obtained by coating and surface treatments i.e. DLC, SIG, SIC+DLC, Al2O3, Al(2)O(3+)Phosphates, CrN, case hardening and boriding were tested both in a "dry sand / rubber wheel" apparatus and in service. The service test was carried out in a vegetable oil factory. The screen bars of an oil extracting press were surface treated and then mounted in the press. After about three months of extracting sunflower oil, the bars were dismantled for the inspection. High pressure in the press together with an abrasive action of the sunflower seed husk showed to be rather detrimental to the surface layers. The best protection of the bars provided a multilayer (SiC+DLC).