Formation of Thick Ni-Al Composite Coating on Spheroidal Graphite Cast Iron Substrates by Reaction Synthesis Processing

Abstract

Thick Ni–Al intermetallic coating was fabricated on a spheroidal graphite cast iron by the reaction synthesis processing. In this study, wear property and bonding strength of the coating layer were estimated. Densification of the coating layer was achieved with increasing holding temperature. Wear property of the coating layers was measured by sliding wear test. While coating layers formed with a hot press temperatures from 873 to 1033 K had superior wear property, the layer fabricated at 873 K for 900 s indicated the best wear resistance. This is considered to be caused by higher hardness of Al₃Ni₂ compound dispersed in the coating layer. Reaction layer was found out at the interface between the coating layer and substrate. The layer was composed of three different phases which were identified as a Al₇Fe₂Ni and FeAl from quantitative EPMA analyses. These layers well bonded the coating layer to the substrate. Mean shear strength of interface was approximately 73 MPa and increased with increasing holding time for reaction synthesis process.