HIGH TEMPERATURE OXIDATION AND HOT CORROSION BEHAVIOUR OF NANO STRUCTURED COATED Co•605 SUPER ALLOY

Abstract

The Cobalt base super alloys are potential materials for high temperature applications due to their very high temperature strength properties. However, High temperature corrosion is a life-limiting factor for Cobalt base alloy. In the present study, Nanostructured Titanium Aluminum Nitride (TiA1N) and Nanostructured Aluminum Chromium Nitride (A1CrN) coatings were deposited by Physical Vapour Deposition (P.V.D) Technique on Cobalt -605super alloy. The oxidation and hot corrosion behaviour of Nanostructured TiA1N and Nanostructured A1CrN has been studies in air and molten salt (40% Na2SO4+ 60% V205) atmosphere under cyclic heating conditions at a temperature of 7000C for 100 and 80 cycles respectively. Each cycle consisted of 1 hour heating at 700M c followed by 20 minutes of cooling in an ambient temperature. Oxidation Kinetics and hot corrosion kinetics were studied using thermogravimatric technique by recording the weight gain at the end of each cycle. Oxidation kinetics showed that the Nanostructured A1CrN coating performed better than Nanostructured TiA1N coating. The hot corrosion kinetics followed the parabolic rate law. Nanostructured A1CrN coated performed better than Nanostructured TiAIN coated Co-605 in molten salt (40% Na2SO4+ 60% V205) atmosphere. The surface morphology of the oxidized and hot corroded samples were studied using X-ray diffraction (XRD), FESEM with EDAX attachment to find the phases present and to understand the degradation mechanisms in oxidized and hot corroded substrate