Cu Addition To The NiAl Intermetallic For Evaluation As A Protective Coating Simulating Dew Point Environment Conditions

摘要

The NiAl intermetallic was a promising engineering material since 20 years up to present days. Their principal overcoming for real applications is their inherent brittleness at room temperature despite their outstanding properties at high or elevated temperatures. Several attempts and investigations including alloying with third element, and processing (thermomechanical treatment, rapid solidification etc) has been done over the last 10 years for achieve ductility at room temperature. However this is not accomplished yet, even having promising results as Colin et al (1) reported macro-alloying the NiAl with Cu and Fe. Due to its poor ductility as a bulk material, some other applications have been realized such as protective coatings at high and room temperature owing to their exceptional corrosion properties. Nevertheless, the solely NiAl system has been proved as protective coating with no success due to rapid Al depletion in magnetron sputtering coatings in Nickel-alloys and Ni_3AI substrates. The objective of the present work is to evaluate the NiAI-Cu intermetallic system employing a thermal spray coating technique, to evaluate the addition of Cu to the NiAl intermetallic as a barrier of Al depletion during the partial meting and re-solidification processes intrinsic to the coating technique. Thus, verifying their effectiveness as a room temperature coating application in H_2SO_4 solution by means of electrochemical techniques, simulating "dew point" conditions that exist in fossil power plants during maintaining schedules. The substrate utilized was nickel alloy 600 that is commonly used in such applications.