Title: Mechanism of Al-Si codeposition on In738LC through single-step diffusion process

Authors: Siamak Nikzad; Mohsen Abdi; Saeed Rastegari

Addresses: Department of Materials Science and Engineering, Sahrif University of Technology, Tehran, Iran ' School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, Iran ' School of Metallurgy and Materials Engineering, Iran University of Science and Technology (IUST), Narmak, Tehran, Iran

Abstract: The out-of-pack cementation method was applied to coat the Nickel-based super alloy IN738LC with Si-modified aluminide. Different mixtures of the pack containing pure Al, Si, alumina powders as an inert filler, and NH₄Cl as a halide salt activator were used for co-deposition at 950 and 1,050°C. The results showed although the amount of subhalide vapour pressures of Al and Si were equal at 1,050°C, Al atoms diffused only after Si atoms had been deposited. Before heat treatment, the coating thickness formed by the pack containing 2.3 wt.% Al was 6 µm more than that containing 3.5 wt.‰ Al. After heat treatment, thickening coatings formed within the pack containing 2.3 wt.% Al was less than that obtained in the other pack containing 3.5 wt.% Al. This study suggests that increasing the depositing temperature will increase the thickness at a constant composition of the pack powder.

Keywords: co-deposition; silicon modified aluminide coatings; heat treatment; single-step diffusion; out-of-pack cementation; nickel superalloys; alumina powders; ammonium chloride; NH4Cl; coating thickness; depositing temperature.

DOI: 10.1504/IJSURFSE.2017.082942

International Journal of Surface Science and Engineering, 2017 Vol.11 No.1, pp.1 - 11

Received: 26 Apr 2015
Accepted: 17 Jan 2016
Published online: 16 Mar 2017 *

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