Production and characterization of Ni-Al based intermetallic coating on hastelloy C-276 alloy

In the field of high temperature applications such as aviation, space exploration and nuclear reactors, Hastelloy C-276 emerges as a very important nickel-based superalloy. Characterized by the composition of basic elements such as Cr, Mo, Fe and W, this alloy is of great importance in both scientific and industrial contexts. Recently, the quest to improve the surface properties of such alloys has led to the widespread adoption of a technique that involves the formation of an aluminum-rich coating. The purpose of this coating is to obtain stable Alumina (Al2O3) at high temperatures. This work focuses on enhancing the surface properties of Hastelloy alloy through the application of a low-temperature package aluminization process, resulting in the formation of an aluminide coating. The aluminization process performed at varying temperatures (600°C, 650°C, and 700°C) and durations (2, 4, and 6 hours) causes significant deposition of intermetallic coatings even within a short process time. Noteworthy is the gradual increase in the thickness of the Ni-Al-based coating layer, from 11 µm to 42 µm, with the increase of temperature. The resulting coating not only increases the hardness values from an initial 250 HV to an impressive 850 HV, but also offers a compelling kinetic energy value of 50,911 kJ/mol. This kinetic energy value is considered an important measurement that provides critical information about the thermodynamics and reaction rate of the aluminization process. Calculations made after coating, taking into account the coating layer thicknesses, contribute to a comprehensive understanding of the formation kinetics of the aluminization process. Temperature and time emerge as important parameters in this analytical process. Additionally, the oxidation resistance and thermal stability properties of the coating are realized through the application of thermogravimetric (TG) thermal analysis methods. These analyses, which examine weight changes during oxidation, provide valuable information about the material's ability to withstand thermal stresses and resist oxidation. Further investigation of the relationship between the depth of the aluminide layer and the growth kinetics with respect to time and process temperature reveals vital insights for optimizing coating performance. Such insights are promising and lead to many studies for more efficient use of these coatings in various industrial applications.