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Formation Mechanism of Aluminide Diffusion Coatings on Ti and Ti-6Al-4V Alloy at the Early Stages of Deposition by Pack Cementation
The diffusion coatings were deposited on commercially pure Ti and Ti-6Al-4V alloy at up to 1000 °C for up to 10 h using the pack cementation method. The pack powders consisted of 4 wt% Al (Al reservoir) and 4 wt% NH(4)Cl (activator) which were balanced with Al(2)O(3) (inert filler). The growth kinet...
Autores principales: | , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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MDPI
2019
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6803934/ https://www.ncbi.nlm.nih.gov/pubmed/31547542 http://dx.doi.org/10.3390/ma12193097 |
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author | Du, Hailiang Tan, Ning Fan, Li Zhuang, Jiajie Qiu, Zhichao Lei, Yanhua |
author_facet | Du, Hailiang Tan, Ning Fan, Li Zhuang, Jiajie Qiu, Zhichao Lei, Yanhua |
author_sort | Du, Hailiang |
collection | PubMed |
description | The diffusion coatings were deposited on commercially pure Ti and Ti-6Al-4V alloy at up to 1000 °C for up to 10 h using the pack cementation method. The pack powders consisted of 4 wt% Al (Al reservoir) and 4 wt% NH(4)Cl (activator) which were balanced with Al(2)O(3) (inert filler). The growth kinetics of coatings were gravimetrically measured by a high precision balance. The aluminised specimens were characterised by means of scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). At the early stages of deposition, a TiO(2) (rutile) scale, other than aluminide coating, was developed on both materials at <900 °C. As the experimental temperature arose above 900 °C, the rutile layer became unstable and reduced to the low oxidation state of Ti oxides. When the temperature increased to 1000 °C, the TiO(2) scale dissociated almost completely and the aluminide coating began to develop. After a triple-layered coating was generated, the coating growth was governed by the outward migration of Ti species from the substrates and obeyed the parabolic law. The coating formed consisted of an outer layer of Al(3)Ti, a mid-layer of Al(2)Ti and an inner layer of AlTi. The outer layer of Al(3)Ti dominated the thickness of the aluminide coating. |
format | Online Article Text |
id | pubmed-6803934 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2019 |
publisher | MDPI |
record_format | MEDLINE/PubMed |
spelling | pubmed-68039342019-11-18 Formation Mechanism of Aluminide Diffusion Coatings on Ti and Ti-6Al-4V Alloy at the Early Stages of Deposition by Pack Cementation Du, Hailiang Tan, Ning Fan, Li Zhuang, Jiajie Qiu, Zhichao Lei, Yanhua Materials (Basel) Article The diffusion coatings were deposited on commercially pure Ti and Ti-6Al-4V alloy at up to 1000 °C for up to 10 h using the pack cementation method. The pack powders consisted of 4 wt% Al (Al reservoir) and 4 wt% NH(4)Cl (activator) which were balanced with Al(2)O(3) (inert filler). The growth kinetics of coatings were gravimetrically measured by a high precision balance. The aluminised specimens were characterised by means of scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD). At the early stages of deposition, a TiO(2) (rutile) scale, other than aluminide coating, was developed on both materials at <900 °C. As the experimental temperature arose above 900 °C, the rutile layer became unstable and reduced to the low oxidation state of Ti oxides. When the temperature increased to 1000 °C, the TiO(2) scale dissociated almost completely and the aluminide coating began to develop. After a triple-layered coating was generated, the coating growth was governed by the outward migration of Ti species from the substrates and obeyed the parabolic law. The coating formed consisted of an outer layer of Al(3)Ti, a mid-layer of Al(2)Ti and an inner layer of AlTi. The outer layer of Al(3)Ti dominated the thickness of the aluminide coating. MDPI 2019-09-23 /pmc/articles/PMC6803934/ /pubmed/31547542 http://dx.doi.org/10.3390/ma12193097 Text en © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). |
spellingShingle | Article Du, Hailiang Tan, Ning Fan, Li Zhuang, Jiajie Qiu, Zhichao Lei, Yanhua Formation Mechanism of Aluminide Diffusion Coatings on Ti and Ti-6Al-4V Alloy at the Early Stages of Deposition by Pack Cementation |
title | Formation Mechanism of Aluminide Diffusion Coatings on Ti and Ti-6Al-4V Alloy at the Early Stages of Deposition by Pack Cementation |
title_full | Formation Mechanism of Aluminide Diffusion Coatings on Ti and Ti-6Al-4V Alloy at the Early Stages of Deposition by Pack Cementation |
title_fullStr | Formation Mechanism of Aluminide Diffusion Coatings on Ti and Ti-6Al-4V Alloy at the Early Stages of Deposition by Pack Cementation |
title_full_unstemmed | Formation Mechanism of Aluminide Diffusion Coatings on Ti and Ti-6Al-4V Alloy at the Early Stages of Deposition by Pack Cementation |
title_short | Formation Mechanism of Aluminide Diffusion Coatings on Ti and Ti-6Al-4V Alloy at the Early Stages of Deposition by Pack Cementation |
title_sort | formation mechanism of aluminide diffusion coatings on ti and ti-6al-4v alloy at the early stages of deposition by pack cementation |
topic | Article |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6803934/ https://www.ncbi.nlm.nih.gov/pubmed/31547542 http://dx.doi.org/10.3390/ma12193097 |
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