Formation of Si-modified Nickel-Aluminide coating applied throughout a single step high activity-high temperature process on Nickel base superalloy

In this research properties of Single-Step High temperature-High activity Si-modified Nickel Aluminide coating on superalloy Inconel 100 at 1000 and 1100˚C have been investigated. Si-modified NiAl coating were prepared using 5 and 10 percent mass of Al and Si powders as well as Al2O3 and NH4Cl activators. Microstructure, phase distribution and coating composition of as-coated specimens were analyzed by using OM, SEM equipped with EDS/WDS and XRD. The results showed that co-precipitation of Al and Si using Single-Step High Temperature-High Activity process can be achieved. By reducing Al and Si amount in the pack from %10 to %5 in mass, the coating depth enriched by Si decrease from 50 to 20μm. In 1 hour, With %10 in mass pack hyperstoichiometric NiAl phase with more than %50 at of Al was formed while after 1 and 3 h aluminizing with %5 in mass pack, hypostoichiometric NiAl phase with less than %50 at of Al was formed. Micro hardness test results have shown that hardness of formed surface coating varies from 449 VHN in substrate to 1003 VHN in interdiffusion zone duo to presence of various carbides with complex composition.