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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 Al 3 Ni 2 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 Al 7 Fe 2 Ni 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.

Joining of copper alloys (BC6) on spheroidal graphite cast iron (FCD) is effective to enhance the wear resistance of sliding parts. By applying combustion synthesis to a joining to FCD and BC6 has possibilities to enable the process at a lower temperature or for a shorter time. In this study, we examined the application of this process as joining of FCD and BC6 by using Ni -Al -Si compact as filler. Then the effects of the interface microstructure on joining were examined. As a substrate, FCD and BC6 cut into a column of 10.5B £ 3 mm were prepared. Ni, Al and Si powders were mixed in the composition of Ni -28 at.%(Al -8 at.%Si), or Ni -78 at.%(Al -8 at.%Si). These powders were die-pressed with a load of 400 MPa for 60 s to the disc shape compact of 10 mm in diameter and 0.5 mm or 0.25 mm in thickness. Dense Ni -Al -Si intermetallic compound coating layer was formed by the combustion synthesis from the elemental mixture of Ni, Al and Si, and was simultaneously bonded with the FCD and BC6 substrate. The composition of the filler was Ni 3 Al, Al 3 Ni 2 and Ni solid solution. Unreacted Ni was almost consumed by the reaction with Al -Si. Densification was achieved in the interface between filler and substrate as well as in the filler due to molten Al -Si in the filler during hot pressing infiltrates well into the interface between filler and substrates and the boundary of each powder. Reaction layer of Ni -Al -Cu was formed in the interface between filler and BC6 achieving chemically bonding. q

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Nickel aluminide based intermetallic compounds were combustion synthesized from a powder mixture of elemental Al, Ni, and Si and were simultaneously bonded with spheroidal graphite cast iron substrate (FCD). Addition of Si to the elemental mixture of Al and Ni was confirmed to be effective both to the densification of combustion synthesized intermetallic compounds and to the joining between compounds and FCD. When the composition of precursor was Ni-69at%Al-9at%Si (Al/Si is the ratio of the eutectic composition), Al3Ni and Al6Ni3Si were mainly combustion synthesized. In the interface between compounds and FCD, reaction layers were formed to the thickness of 10 µm and the constituent phases were identified as Al7Fe2Si, FeAl3 respectively. In the four point bending test of the dissimilar joints prepared by heating at 973 K for 300 s, the brittle fracture did not occurred around the joint interface but mainly in the inside of nickel aluminide coating. The interface of reaction layers with 10 µm were chemically well bonded. The sample with Ni-69at%Al-9at%Si coating exhibited highest bonding strength of about 56 MPa because of the smallest void ratio of the obtained compounds.