Systematic Wear/Corrosion Study Analysis of Ion Plated Surfaces

摘要

This study deals with the improvement in localized corrosion resistance and wear reduction of type M-50 steel used in engineering components such as bearings by use of overlay coating. Overlay coating materials selected for the improvement in localized corrosion (pitting) were titanium, chromium, nichrome (Ni-20Cr) and molybdenum deposited by physical vapor deposition techniques of direct evaporation (E), activated evaporation (AE), i.e. evaporation in the presence of a plasma, and ion plating (IP), and titanium carbide, titanium nitride and hafnium nitride coatings deposited by the activated reactive evaporation process (ARE). Coated and control (uncoated) samples of M-50 steel were corrosion tested. The results showed that the control (uncoated) samples were severly pitted along the contact line and general corrosion occurred outside this region, whereas the samples with overlay coatings of titanium, chromium, nichrome (Ni-20Cr), TiC, and TiN completely eliminated the localized pitting corrosion. Coatings of these materials deposited by different techniques showed equally good results. Overlay coatings of molybdenum showed corrosion presumably due to the reaction with the sulfur content of the polyester oil. Hafnium nitride coating also showed pitting in the areas where the coating had peeled off the substrate after deposition and prior to the corrosion test.