NICOP - Development of Re(Al,Si)1.8 Coating Systems on Nb-Hf Alloys and Its Oxidation Property at High Temperatures
Abstract
1 Title of the proposed research projectDevelopment of Re(Al,Si)1.8 Coating Systems on Nb-Hf Alloysand Its Oxidation Property at H""igh Temperatures2 Principle InvestigatorName Narita ToshioPresident, Emeritus Professor Hokkaido UniversityAddress 3-515-1 Zenib""ako, Otaru 047-0261 JapanDBC System R&D Co., Ltde-mail dbc@dbcsystem.co.jp3 The back ground and basic ideaNiobium-base alloys ha""ve the highest specific strength at elevated temperatures,while they suffer from severe degradation due to high temperature oxidati"on. A Nb-Hfbased alloy (C103) has been used for LBF bipropellant engines. A number ofinvestigations have been conducted to form pr"otective SiO2 and/or Al2O3 scales.Although the NbSi2 coating has much attention, there are several subjects. One of themis a forma"tion of non-protective Nb5Si3 on the NbSi2 layer due to selective Si oxidationand the other degradation of coating structure due to the inter-diffusion between thecoating and alloy substrate.Narita et al proposed the coating with Re-based diffusion barrier laye"r onNb-Mo-W alloys. Meanwhile, suppression of the Nb5Si3 formation is still opened fordiscussion. In this investigation a concept"" of the self-mending coating system will beproposed, based on the phase diagrams for the Re-Nb-Si and Re-Nb-Si-Al systems. Theself""-mending coating system on Nb, Nb-Hf and Nb-17at%Si alloys is developed with anouter ReSi1.8 or Re(Si,Al)1.8, an intermediate (Re,W"",Mo,Nb)Si2, and an inner NbSi2,followed by a transient Nb5Si3. Changes in structures and compositions during hightemperature oxida""tion are investigated and they will be discussed.A two-step process will be adopted, firstly a formation of Re-W-Cr-Ni alloy layer"" byelectroplating of Re-Ni, Cr, Ni-W and Ni from an aqueous solutions followed by heating in vacuumat high temperatures, and secon"dary the Al-reservoir layer of ~-NiAl and Pt-modified ~-NiAl and~~-Ni3Al was formed on the barrier layer.
Document Details
- Document Type
- DoD Grant Award
- Publication Date
- Jan 23, 2018
- Source ID
- N629091812055
Entities
People
- Toshio Narita
Organizations
- Office of Naval Research
- United States Navy