Evidence of Mechanical Interlocking of NiCr Particles Thermally Sprayed onto Al Substrates

• Published in: Journal of thermal spray technology Vol. 14; no. 4; pp. 524 - 529
• Main Authors: Trompetter, W J, Markwitz, A, Hyland, M, Munroe, P
• Format: Journal Article
• Language: English
• Published: New York Springer Nature B.V 01.12.2005
• Subjects: Aluminum; Aluminum base alloys; Bonding; Cross sections; Instability; Locking; Scanning electron microscopy; Substrates; Turbulent flow
• ISSN: 1059-9630; 1544-1016
• DOI: 10.1361/105996305X76568

Ni-chrome alloy particles were thermally sprayed onto aluminum substrates using the high-velocity air fuel technique. The particle substrate interface was investigated with focused ion beam microscopy, crosssectional scanning electron microscopy, and cross-sectional transmission electron microscopy. No evidence of melting or chemical bonding was found in the samples. Instead, evidence of mechanical bonding was found that had been predicted by a previous theoretical study by Grujicic et al. At locations where the particle and substrate are in intimate contact, the interface exhibited interlocking features. These features are caused by the effects of turbulence due to interfacial instability and mixing at the interface during the coating process, resulting in a strong particle-substrate bond. Conversely, separated interfaces exhibited smooth surfaces, suggesting insignificant bonding between the particle and the substrate. The discovery of these interfacial formations, together with no evidence of chemical bonding across the particle-substrate interface indicate that mechanical interlocking is the dominant bonding mechanism.