Protective Nickel Silicide Coating on Inconel 738 Superalloy: Microstructure and Wear Behavior

Abstract

Silicides with potential to form a protective silica layer have attracted significant attention in recent years in protecting engineering materials. This study reports on the formation process and microstructural, mechanical and wear behaviour evolution of Ni-silicide layers formed by pack siliconizing of Inconel 738 alloy at deposition temperatures between 800 and 900 degrees C for 2, 4 h. SEM results reveal that NiSi based intermetallic coatings are obtained successfully on the surface of the Ni Based Alloy. XRD results show that NiSi, Ni3Si2, Ni2Si phases are the main constituents of the coatings and Cr-rich phase forms on the surface of siliconized coatings thanks to the high Cr content of the Inconel 738 Alloy. Surface hardness and wear resistance of the Inconel 738 are dramatically improved by siliconizing. However, the results were affected by the type of silicide layer. It was observed that the Cr rich silicide layer was much more successful in hardness and wear resistance.