Resistance to electrochemical corrosion of CrxNy- and DLC-coated steel tools in the environment of wet wood

We have shown in an earlier work that in wood machining the degree of blunting of steel knives due to electrochemical corrosion is small as compared to their abrasive wear. However, the corrosion of steel knives may occur during the cut-offs of the machining operation, when the knife does not work but is still covered with the extract of wood in water. The anti-abrasive coatings deposited on steel knives may also protect them against corrosion. The aim of the present study was to examine how coatings with good anti-abrasive properties (CrxNy and DLC) can protect low-Cr steel against electrochemical corrosion. The corrosion of the coated steels did not depend noticeably on the kind of wood, despite the difference in the pH value of their water suspensions. All the coatings appeared to improve the corrosion resistance of the steel. The best results were achieved with the DLC coating deposited by cathodic arc evaporation and CrN + Cr2N coating deposited by magnetron sputtering, although steel covered with these layers has shown pitting corrosion.