An investigation on the properties of chromium-modified aluminide coating on Ni-base superalloy IN-738LC

摘要

The most severe problem in failure of land base industrial gas turbines that are extensively used in oil and gas pipelines is hot corrosion in their first stage turbine blades and vanes. Mostly because of the presence of high temperature and detrimental impurities in fuel and/or in air introduced to these turbines. For improvement of hot corrosion resistance of these parts that are made from nickel or cobalt base superalloys, they are usually protected with a suitable coating. Diffusion aluminide coating is one of the most common coatings used for turbine blades the hot corrosion resistance of which can be improved by various methods such as the addition of chromium, platinum, etc. In the present work, a nickel base superalloy, IN-738LC, was coated with chromium-modified aluminide using two separate diffusion processes including chromizing and aluminizing. Optical and scanning electron microscopy methods were used to study the microstructural feature of coatings. In order to determine the composition and the distribution of the elements in the coatings, an X-ray microanalysis technique was employed, and phase characterization was also carried out using an XRD technique. Finally, the effect of coating process parameters on the coating properties are discussed.