Microstructure and oxidation behavior of the aluminized coating on K447A nickel-based superalloy prepared by AlF3-activated pack cementation

IF 5.3 2区材料科学 Q1 MATERIALS SCIENCE, COATINGS & FILMS

Surface & Coatings Technology Pub Date : 2025-05-03 DOI:10.1016/j.surfcoat.2025.132236

Yuhang Zhao , Kai Zhou , Xin Xin , Xijun Zeng , Xiping Guo , Yanqiang Qiao

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引用次数: 0

Abstract

The function of AlF₃ activator, the aluminized coating formation mechanism on K447A nickel-based superalloy during the pack cementation process, and their oxidation behaviors have been systematically investigated. Comprehensive characterization by XRD, SEM, TEM and EDS analyses with HSC thermochemical calculation reveals four key findings: AlF₃ demonstrates the optimal aluminizing capability and generates active Al atoms via the disproportionation reaction of AlF gas. The aluminized coating exhibits a multilayer structure, with the outer layer composed of high Al content Ni₂Al₃ or NiAl₃ and the inner layer consisting of NiAl. Precipitated phases such as α-(Cr, W), σ phase, and carbides are distributed in the aluminides, confirming an Al-dominated inward diffusion mechanism characteristic of a “high-activity” process. The coating thickness exhibits linear relationships to the reciprocal of temperature and holding time. Ni₂Al₃ is formed before NiAl, transforms into NiAl, and then is regenerated. After oxidizing at 1150 °C for 100 h, a protective ridged α-Al₂O₃ scale forms on the aluminide coating, effectively shielding the substrate.

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alf3活化包埋法制备K447A镍基高温合金渗铝涂层的组织与氧化行为

系统地研究了AlF3活化剂的作用、K447A镍基高温合金包埋过程中镀铝层的形成机理及其氧化行为。通过XRD、SEM、TEM、EDS等综合表征及HSC热化学计算，得出了四个主要发现：AlF3表现出最佳的渗铝能力，并通过Al气体的歧化反应生成活性Al原子；渗铝涂层呈多层结构，外层由高铝含量的Ni2Al3或NiAl3组成，内层由NiAl组成。析出相如α-（Cr， W）、σ相和碳化物分布在铝化物中，证实了al主导的“高活性”向内扩散机制。涂层厚度与温度和保温时间呈线性关系。Ni₂Al₃在NiAl之前形成，转化为NiAl，然后再生。在1150℃氧化100 h后，氧化铝涂层上形成一层脊状α-Al2O3保护膜，有效地屏蔽了基体。

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来源期刊

Surface & Coatings Technology 工程技术-材料科学：膜

CiteScore

10.00

自引率

11.10%

发文量

921

审稿时长

19 days

期刊介绍： Surface and Coatings Technology is an international archival journal publishing scientific papers on significant developments in surface and interface engineering to modify and improve the surface properties of materials for protection in demanding contact conditions or aggressive environments, or for enhanced functional performance. Contributions range from original scientific articles concerned with fundamental and applied aspects of research or direct applications of metallic, inorganic, organic and composite coatings, to invited reviews of current technology in specific areas. Papers submitted to this journal are expected to be in line with the following aspects in processes, and properties/performance: A. Processes: Physical and chemical vapour deposition techniques, thermal and plasma spraying, surface modification by directed energy techniques such as ion, electron and laser beams, thermo-chemical treatment, wet chemical and electrochemical processes such as plating, sol-gel coating, anodization, plasma electrolytic oxidation, etc., but excluding painting. B. Properties/performance: friction performance, wear resistance (e.g., abrasion, erosion, fretting, etc), corrosion and oxidation resistance, thermal protection, diffusion resistance, hydrophilicity/hydrophobicity, and properties relevant to smart materials behaviour and enhanced multifunctional performance for environmental, energy and medical applications, but excluding device aspects.