Chong Zhang, Jinchao Yang, Rui Lin, Chao Shen, Lian Zuo, Zhiyu Hu, Chuming He
{"title":"Formation mechanism and oxidation performance for a novel Mo(Si,Al)2 coating prepared using a modified pack cementation strategy","authors":"Chong Zhang, Jinchao Yang, Rui Lin, Chao Shen, Lian Zuo, Zhiyu Hu, Chuming He","doi":"10.1016/j.surfcoat.2024.131574","DOIUrl":null,"url":null,"abstract":"<div><div>Using a modified Si-Al deposition strategy in the process of halide-activated pack cementation, conventional and novel Mo(Si,Al)<sub>2</sub> coatings are fabricated on molybdenum substrate to assess their distinct formation mechanism and oxidation performance. The results show that the conventional coatings are composed of an inner layer containing pure C11b MoSi<sub>2</sub> and an outer layer containing C11b MoSi<sub>2</sub> with a little Al. By contrast, the new coating is composed of pure C22 Al<sub>8</sub>Mo<sub>3</sub> as the inner layer and C40 Mo(Si,Al)<sub>2</sub> as the outer layer (unexpectedly low Al percentage of 13 at.%). Notably, the two kinds of coatings have different microstructures and formation characteristics. The former's synthesis pathway includes the sequential formation of C22 Al<sub>8</sub>Mo<sub>3</sub>, C40 Mo(Si,Al)<sub>2</sub>, and C11b MoSi<sub>2</sub>, accompanied by a reduction in the proportion of solidified Al in Mo(Si,Al)<sub>2</sub>. The latter's synthesis path includes the transformation from C11b MoSi<sub>2</sub> to C40 Mo(Si,Al)<sub>2</sub>, and the Al content is always maintained at the highest level with the coating growth. Meanwhile, the phase transition between Al<sub>8</sub>Mo<sub>3</sub> and Mo(Si,Al)<sub>2</sub> is an irreversible process and neither coating forms the C54 structure of Mo(Si,Al)<sub>2</sub> due to the low temperature. Besides, the different oxidation mechanisms are elucidated on basic of the two deposition procedures and corresponding to oxidation performance. Hence, the newly developed Mo(Si,Al)<sub>2</sub> coating of first silicon and then aluminum in the process of pack-cementation can be effectively used to fabricate a protective α-Al<sub>2</sub>O<sub>3</sub> barrier layer at a temperature of 1300 °C.</div></div>","PeriodicalId":22009,"journal":{"name":"Surface & Coatings Technology","volume":"496 ","pages":"Article 131574"},"PeriodicalIF":5.3000,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":"0","resultStr":null,"platform":"Semanticscholar","paperid":null,"PeriodicalName":"Surface & Coatings Technology","FirstCategoryId":"88","ListUrlMain":"https://www.sciencedirect.com/science/article/pii/S0257897224012052","RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":null,"EPubDate":"","PubModel":"","JCR":"Q1","JCRName":"MATERIALS SCIENCE, COATINGS & FILMS","Score":null,"Total":0}
引用次数: 0
Abstract
Using a modified Si-Al deposition strategy in the process of halide-activated pack cementation, conventional and novel Mo(Si,Al)2 coatings are fabricated on molybdenum substrate to assess their distinct formation mechanism and oxidation performance. The results show that the conventional coatings are composed of an inner layer containing pure C11b MoSi2 and an outer layer containing C11b MoSi2 with a little Al. By contrast, the new coating is composed of pure C22 Al8Mo3 as the inner layer and C40 Mo(Si,Al)2 as the outer layer (unexpectedly low Al percentage of 13 at.%). Notably, the two kinds of coatings have different microstructures and formation characteristics. The former's synthesis pathway includes the sequential formation of C22 Al8Mo3, C40 Mo(Si,Al)2, and C11b MoSi2, accompanied by a reduction in the proportion of solidified Al in Mo(Si,Al)2. The latter's synthesis path includes the transformation from C11b MoSi2 to C40 Mo(Si,Al)2, and the Al content is always maintained at the highest level with the coating growth. Meanwhile, the phase transition between Al8Mo3 and Mo(Si,Al)2 is an irreversible process and neither coating forms the C54 structure of Mo(Si,Al)2 due to the low temperature. Besides, the different oxidation mechanisms are elucidated on basic of the two deposition procedures and corresponding to oxidation performance. Hence, the newly developed Mo(Si,Al)2 coating of first silicon and then aluminum in the process of pack-cementation can be effectively used to fabricate a protective α-Al2O3 barrier layer at a temperature of 1300 °C.
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.
京公网安备 11010802042870号
京ICP备2023020795号-1
分享
求助内容：
应助结果提醒方式：
扫码关注我们
