|
Title
|
Optimization of Heat Treatment Cycles in Sub-atmospheric LiF-NaF-KF Based Fluoride Ion Cleaning for Removing Oxide Layers in Cracks of IN738-LC
|
|
Type
|
JournalPaper
|
|
Keywords
|
Alkaline fluoride salts, Cleaning; Micrograph, Oxide films, Superalloy, Cracks
|
|
Abstract
|
An improved fluoride ion cleaning (FIC) process for removing all oxide layers utilizing a molten mixture of alkaline fluoride salts in sub-atmospheric pressure was developed and applied to the oxide layers on cracks formed on the surface of Inconel 738-LC samples. This method is characterized directly by filling-up the cracks with a molten mixture of alkaline fluoride salts (LiF-NaF-KF) overheating up under sub-atmospheric pressure and subsequently injection of hot hydrogen gas into the process chamber. The effect of cleaning time on the microstructure of the finished surface was studied in time durations up to 120 min in 30 min time intervals by using cross-sectional micrographs and elemental distribution maps. In accordance with the mass loss amounts and microstructural studies during the cleaning process, the optimum cleaning time suggested being 90-120 min. Perquisite microstructural discern that in the suggested cleaning condition all oxide scales in the cracks will be removed without applying any extra damage to the gamma prime depleted layer, which is a necessary layer for the prevention of sample oxidation before repair. Because subsequent brazing operations need an oxide-free surface.
|
|
Researchers
|
Hamid Esfahani (Fourth Researcher), Mohammad Javad Eshraghi (Third Researcher), mohammad reaza rahimi pour (Second Researcher), Sara Hamidi (First Researcher)
|