Journal of Advanced Materials and Technologies

Journal of Advanced Materials and Technologies

Microstructural Investigation of Silicon‑Modified Aluminide Coatings on IN792 Superalloy via Low‑Activity Out‑of‑Pack Cementation

Document Type : Original Reaearch Article

Authors
Ali Azari Beni 1
saeed rastegari 2
Masoud Hasheminiasari 2
1 PhD Student, School of Materials and Metallurgical Engineering, Iran University of Science and Technology, Tehran, Tehran, Iran.
2 Associate Professor, School of Materials and Metallurgical Engineering, Iran University of Science and Technology, Tehran, Tehran, Iran.
10.30501/jamt.2026.577423.1359
Abstract
Silicon-modified aluminide coatings on nickel-based superalloys often suffer from brittleness due to surface-enriched silicide phases. This study introduces a low-activity out-of-pack cementation process conducted at 1050 °C for 240 min under argon to co-deposit Al and Si on the IN792 superalloy, aiming to confine brittle silicides to the inner regions while maintaining a ductile surface. Four powder mixtures with a fixed Al content of 10 wt.% and varying Si contents (0, 5, 10, and 15 wt.%) were used. The simple aluminide coating (sample O, 0% Si) exhibited a dual-layer structure with a total thickness of 45.5 µm, consisting of an outer β-NiAl layer (28.4 µm) and an interdiffusion zone (17.1 µm). The addition of Si reduced the total coating thickness in a nonlinear manner to 42.5 µm (5% Si, sample S3), 44.4 µm (10% Si, sample S2), and 25.6 µm (15% Si, sample S1). The highest Si content (15%) resulted in the greatest reduction, corresponding to an approximately 44% decrease compared with sample O. EDS mapping confirmed that outward Ni diffusion remained the dominant coating growth mechanism in all samples. Importantly, Si enrichment was observed primarily within the interdiffusion zone and at the coating/substrate interface rather than in the outer β-NiAl layer, explaining the absence of silicide peaks in the XRD patterns. This microstructure, consisting of a ductile β-NiAl surface layer over a silicide-rich subsurface region, offers a viable strategy for overcoming brittleness while retaining the oxidation resistance of Si-modified aluminide coatings.
Keywords
IN792 Superalloy
Out of Pack Cementation
Silicon Modified Aluminide Coatings
Low Activity Aluminizing
Subjects
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Journal of Advanced Materials and Technologies
Volume 15, Issue 1
Spring 2026
Pages 69-84

  • Receive Date 22 February 2026
  • Revise Date 25 May 2026
  • Accept Date 19 June 2026