High-Temperature Oxidation and Corrosion Behaviour of APS CoCrAlY + Cr3C2–NiCr Composite Coating

• Published in: Journal of bio- and tribo-corrosion 2020, Vol.6 (2), Article 28
• Main Authors: Nithin, H. S., Nishchitha, K. M., Shamanth, V., Hemanth, K., Babu, K. Anand
• Format: Article
• Language: English
• Subjects: Adhesive strength; Base metal; Biomaterials; Chemistry and Materials Science; Chromium; Chromium carbide; Coatings; Corrosion; Corrosion and Coatings; Corrosion rate; Corrosion resistance; Corrosion tests; Gas turbines; High temperature; Hot corrosion; Materials Science; Microhardness; Oxidation; Oxidation resistance; Protective coatings; Reaction kinetics; Scale (corrosion); Scanning electron microscopy; Sodium sulfate; Solid Mechanics; Spectroscopy; Substrates; Tribology; Vanadium pentoxide; Weight; X-ray diffraction
• ISSN: 2198-4220; 2198-4239
• DOI: 10.1007/s40735-020-0322-9

An approach of chrome carbide-based composite coating entailing of hard phase (Cr 3 C 2 –NiCr) and matrix-CoCrAlY was tailored to encounter the severe environments such as elevated temperature oxidation, corrosion and erosion in gas turbine application. CoCrAlY +  Cr 3 C 2 –NiCr coating was deposited by atmospheric plasma spray process. Oxidation and hot corrosion tests were conducted under cyclic conditions in Na 2 SO 4 –V 2 O 5 salt environment at 700 °C. The oxidation and hot corrosion behaviour base metal and coated samples were evaluated by thermogravimetric method. Scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDS) and X-ray diffraction techniques were used to characterize the tested samples in terms of elemental and phase analysis. Microhardness of the composite coating is 318 ± 26 HV and the adhesion strength is found to be 11.5 ± 2.5 MPa. The uncoated alloys exhibited limited weight gain for the initial oxidation cycles followed by linear weight gain curve with the increasing in thermocycles. The CoCrAlY +  Cr 3 C 2 –NiCr coating experienced good corrosion resistance as compared to substrates- MDN 321 and Superni 76 at 700 °C. The coatings subjected to oxidation and hot corrosion showed slow-scale growth kinetics with parabolic rate constant (Kp) value of 0.4 and 0.053 10 –10  g 2  cm −4  s −1 , respectively. The higher Cr content in the coating resulted in the growth of Cr 2 O 3 and its spinel CoCr 2 O 4 as a strong phase is beneficial for oxidation and corrosion resistance.