A literature study of the etching process on nickel- and titanium-based superalloys - The chemical reactions at the metal-liquid interface
Typ
Examensarbete för masterexamen
Master's Thesis
Master's Thesis
Program
Materials chemistry (MPMCN), MSc
Publicerad
2024
Författare
Appelqvist, Henrik
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
In the aerospace industry, the requirement for material properties and product safety are among the most important factors to consider in order to ensure the safety and reliability of the aircrafts. During the manufacturing process, the formation of cracks in the material might occur. For example, polishing of a region in the close vicinity of a crack can smear the metallic material over the cracks. This would result in that the crack could go undetected through quality control. Additionally, the oxides formed during heat treatment were shown to have high chemical stability and would cause trouble during removal.
Therefore, in this literature study, the oxidation behavior of nine highly relevant aerospace materials were examined together with the effect of six common etching solutions. Furthermore, the relationship between etch rate with temperature and concentration of each etching solution was also explored.
The study found that the pure metals, in most cases, were dissolved by the etching solutions with a few exceptions where passive reaction products were formed on the surface. Passive reaction products restricted diffusion of metallic elements out towards the oxidizing environment and vice versa. These would instead have the opposite effect on the etch rate where it would decrease as the reaction progressed due to the growing thickness of the metal oxides. A similar behavior could be seen by the metal oxides, but the oxidizing etching solutions and the acetic acid, weak acid, could not affect the metal oxides. An increased temperature and concentration of etching solution, did in most cases lead to an increased rate. Exceptions from the trend showed that some acids had an optimal concentration at which the reaction could ensue. The primary variable was the acids ability to dissociate which occurs when water is present. Therefore, the etch rate would decrease at very high concentrations due to the lack of water.
Although this literature study can give an insight in the etching process, or more specifically the reactions that occur at the interface between the metallic material and the etching solution, further work is needed to achieve a deeper understanding of the application on a larger scale.
Beskrivning
Ämne/nyckelord
Superalloy , Etching , Titanium-based , Nickel-based , Dissolution , Corrosion