Advanced Coatings on High Temperature Applications

2006 ◽  
Vol 522-523 ◽  
pp. 1-14 ◽  
Author(s):  
Toshio Narita ◽  
Takeshi Izumi ◽  
Takumi Nishimoto ◽  
Yoshimitsu Shibata ◽  
Kemas Zaini Thosin ◽  
...  
Keyword(s):  
High Temperature ◽  
Diffusion Barrier ◽  
Layer Structure ◽  
Diffusion Coating ◽  
Alloy Layer ◽  
Outward Diffusion ◽  
Hastelloy X ◽  
Alloy Substrate ◽  
Barrier Coating ◽  
Ni Alloy

To suppress interdiffusion between the coating and alloy substrate in addition to ensuring slow oxide growth at very high temperatures advanced coatings were developed, and they were classified into four groups, (1) the diffusion barrier coating with a duplex layer structure, an inner σ−(Re-Cr-Ni) phase as a diffusion barrier and outer Ni aluminides as an aluminum reservoir formed on a Ni based superalloy, Hastelloy X, and Nb-based alloy. (2) the up-hill diffusion coating with a duplex layer structure, an inner TiAl2 + L12 and an outer β-NiAl formed on TiAl intermetallic and Ti-based heat resistant alloys by the Ni-plating followed by high Al-activity pack cementation. (3) the chemical barrier coating with a duplex layer structure, an inner* γ + β + Laves three phases mixture as a chemical diffusion barrier and an outer Al-rich γ-TiAl as an Al reservoir formed by the two step Cr / Al pack process. (4) the self-formed coating with the duplex structure, an inner α-Cr layer as a diffusion barrier and an outer β-NiAl as an Al-reservoir on Ni-(2050)at% Cr alloy changed from the δ-Ni2Al3 coating during oxidation at high temperature. The oxidation properties of the coated alloys were investigated at temperatures between 1173 and 1573K in air for up to 1,000 hrs (10,000 hrs for the up-hill diffusion coating). In the diffusion barrier coating the Re-Cr-Ni alloy layer was stable, existing between the Ni-based superalloy (or Hastelloy X) and Ni aluminides containing 1250at%Al when oxidized at 1423K for up to 1800ks. It was found that the Re-Cr-Ni alloy layer acts as a diffusion barrier for both the inward diffusion of Al and outward diffusion of alloying elements in the alloy substrate. In the chemical barrier coating both the TiAl2 outermost and Al-rich γ-TiAl outer layers maintained high Al contents, forming a protective Al2O3 scale, and it seems that the inner, γ, β, Laves three phase mixture layer suppresses mutual diffusion between the alloy substrate and the outer/outermost layers.

The Role of Bond Coat in Advanced Thermal Barrier Coating

2005 ◽  
Vol 502 ◽  
pp. 99-104 ◽  
Author(s):  
Toshio Narita ◽  
Shigenari Hayashi ◽  
Feng Qun Lang ◽  
Kemas Zaini Thosin
Keyword(s):  
Diffusion Barrier ◽  
Bond Coat ◽  
Sigma Phase ◽  
Oxidation Behavior ◽  
Layer Structure ◽  
Thermal Barrier ◽  
Outward Diffusion ◽  
Hastelloy X ◽  
Barrier Coating

A novel diffusion barrier bond coat with a duplex layer structure, a sigma phase Re-Cr-Ni barrier and Ni aluminides as an aluminum reservoir was formed on a Ni based superalloy (TMS 82+) and Hastelloy X. The oxidation behavior of both alloys with and without the sigma- Re-Cr-Ni -phase as a diffusion barrier was investigated at temperatures of 1373K (Hastelloy X) and 1423K (TMS-82+) for up to 360ks. It was found that the Re-Cr-Ni acts as a diffusion barrier for both inward diffusion of Al and outward diffusion of alloying elements in the alloy substrate.

Creep Deformation / Oxidation Behavior of Re-Cr-Ni Diffusion Barrier Coated Hastelloy-X at 970°C in Air

2008 ◽  
Vol 595-598 ◽  
pp. 107-116 ◽  
Author(s):  
Shigenari Hayashi ◽  
Mikihiro Sakata ◽  
Shigeharu Ukai ◽  
Toshio Narita
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Barrier Layer ◽  
Creep Deformation ◽  
Diffusion Barrier ◽  
Hastelloy X ◽  
Alloy Substrate ◽  
Barrier Coating ◽  
Diffusion Barrier Layer ◽  
Coated Alloy

High temperature oxidation / creep deformation behavior of a diffusion barrier coated Hastelloy-X alloy, with large grain size ~500μm, was investigated at 970°C in air with external tensile stress of 22.5, 27.5, 32, and 40MPa. The diffusion barrier coating formed on Hastelloy-X consisted of a duplex structure with an inner diffusion barrier layer of Re-Cr-Ni alloy, and an outer oxidation resistant layer of β-NiAl. Un coated bare Hastelloy-X alloy with same grain size was also examined under the same conditions for comparison. The composition of the as-coated diffusion barrier coating was (15~21)Ni, (33~37)Cr, (30~33)Re, (11~15)Mo, and (9~14)Fe. This composition corresponds to σ-phase in the Ni-Cr-Re ternary system, which is known as a topologically close packed, TCP phase. The composition of this diffusion barrier layer did not change during the experiment. The oxide scales formed after creep testing on the coated and un-coated alloy surfaces were needle-like θ-Al2O3, and Cr2O3 with small amount of FeCr2O4, respectively. Grain boundary oxidation was also found in the subsurface region of the un-coated alloy. The Al2O3 scale exhibited severe spallation, and many cracks were formed perpendicular to the stress direction. However, no spallation or cracks were observed in the Cr2O3. The creep rupture times for the diffusion barrier coated alloy were about 1.5 times longer than those for bare alloy at all creep stress conditions. The fracture surface after rupture indicates that fracture occurred along alloy grain boundaries in both the coated and un-coated alloy substrate. Many cavities and cracks were observed within the diffusion barrier coated alloy substrate. These cavities and cracks tended to propagate from the substrate toward the diffusion barrier layer, and then stopped at the Re-Cr-Ni / β-NiAl interface. Cracks formed in the un-coated alloy initiated at the tip of grain boundary oxides, and propagated into alloy substrate. However no major cavities were observed inside the alloy substrate. The stress index, n, for both specimens was about 6, and this indicates that the deformation mechanism of both samples was dislocation creep. These results suggest that the Re-Cr-Ni diffusion barrier layer acts as a barrier against the movement of dislocations at the interface with the alloy surface.

scholarly journals Alloy Layer Structure Formed by High-temperature Aluminizing in Metal Mold Steel SKD61

2009 ◽  
Vol 95 (6) ◽  
pp. 483-488 ◽  
Author(s):  
Taisuke Odo ◽  
Tomohiro Sasaki ◽  
Takao Yakou ◽  
Akihiro Umeda ◽  
Masahide Tomaru
Keyword(s):  
High Temperature ◽  
Layer Structure ◽  
Alloy Layer ◽  
Metal Mold

High-Temperature Corrosion of Aluminized Diffusion-Coating for Fe-Base Alloy in N2/H2O/H2S-Mixed Gas

2017 ◽  
Vol 16 ◽  
pp. 37-40
Author(s):  
Min Jung Kim ◽  
Dong Bok Lee
Keyword(s):  
High Temperature ◽  
Base Alloy ◽  
Diffusion Coating ◽  
Alumina Scale ◽  
High Temperature Corrosion ◽  
Low Carbon ◽  
Mixed Gas ◽  
High Concentration ◽  
Temperature Oxidation ◽  
Outward Diffusion

The pack-cementation is one of economical, efficient coating processes for Fe-base alloys. It can provide good protection against high-temperature oxidation and corrosion. In this study, the high-temperature corrosion behavior of the aluminized diffusion-coating on low-carbon T20 steel (Fe-2.0Cr-0.5Mo-0.8Mn-0.3S in at.%) was studied at 800 °C in N2/H2O/H2S-mixed gas. The aluminized coating consisted of Fe3Al. The aluminized T20 steel after corrosion at 800 °C for 10~100h in N2/H2O/H2S-mixed gases, the scale formed on the Fe3Al coating consisted primarily of α-Al2O3, Al2S3, FeAl2O4 and FeO, with relatively slow scaling rates. The Fe3Al intermetallics has reasonable corrosion-and oxidation-resistance, because it can form a protective alumina scale. Without the aluminized diffusion-coating, T20 steel corroded fast with serious scale failure. At the surface, coarse FeS grains with cracks formed. Since FeS has a very high concentration of cation vacancies, it grew fast through the outward diffusion of Fe2+ ions.

Development of an Oxidation Resistant Coating on Nb-Based Ultra-High Temperature Alloy

2006 ◽  
Vol 522-523 ◽  
pp. 309-316 ◽  
Author(s):  
Kosuke Saito ◽  
Shigenari Hayashi ◽  
Toshio Narita ◽  
Isao Iwanaga ◽  
Ryohei Tanaka
Keyword(s):  
High Temperature ◽  
Layer Structure ◽  
Pack Cementation ◽  
Temperature Oxidation ◽  
Outward Diffusion ◽  
Alumina Crucible ◽  
Coated Alloy ◽  
Oxidation Resistant ◽  
Α Al2o3 ◽  
Layer Coating

A coating with a duplex layer structure, outer β-NiAl and inner σ-Re-Cr-Ni layers, was formed on the third generation Nb-5Mo-15W-16Si- 5Hf-5C alloy by using successively Re-pack cementation, electroplating of Re-Ni film, and Cr/Al pack cementation. The duplex layer coating changed during high temperature oxidation to form a coating with a four layer structure: an outermost Ni2Al3, an outer Ni, an inner σ-Re-Cr-Ni, and an innermost χ-Re-Nb. The Re-pack cementation was carried in an alumina crucible where the specimen was buried in Re metal powder, in vacuum at 1573K to form a Re film, and then a Re-Ni film was electroplated onto the Re-pack treated alloy. The coated alloy formed a protective α-Al2O3 scale when oxidized at 1573K in air for 14.4ks. It was concluded that the σ-Re-Cr-Ni phase can act as a diffusion-barrier against both inward Al diffusion and outward diffusion of alloying elements from the alloy substrate to the β-NiAl.

scholarly journals Investigations on the Deposition and the Efficiency of a Multilayer High Temperature Coating System for Gas Turbine Blades

1999 ◽  
Author(s):  
Erich Lugscheider ◽  
Ulrich Eritt ◽  
Gunter von Hayn ◽  
Dieter Neuschuetz ◽  
Juergen Mueller
Keyword(s):  
High Temperature ◽  
Gas Turbine ◽  
Diffusion Barrier ◽  
Turbine Blades ◽  
Multilayer Coating ◽  
Atmospheric Plasma ◽  
Neutral Atmosphere ◽  
Coating System ◽  
Gas Turbine Blades ◽  
Barrier Coating

The content of this work is the development and investigation of a high temperature coating system for gas turbine blades. On a single crystal CMSX4 substrate a thin CVD layer of alpha-alumina was deposited as a diffusion barrier coating. As a protection against high-temperature corrosion it was covered with a PVD NiCoCrAlY layer, which also performs as a bond-coat for the following thermal barrier coating deposited by Atmospheric Plasma Spraying. The surface preparation techniques and coating parameters for the multilayer coating were optimized with respect to the bonding mechanisms of the different deposition techniques. The samples were annealed at 1100°C for 100 h under a neutral atmosphere. Furthermore thermocycle experiments were carried out to investigate thermocycle behaviour. The coating system proved its efficiency: no cracks were observed except vertical segmentation cracks in the TBC, all layers showed good adhesion and the diffusion barrier remained intact suppressing any noticeable diffusion of Al, Cr, Ta, Re, W and Ti.

Interdiffusion between Ni Based Superalloy and Diffusion Barrier Coatings at 1423K

2006 ◽  
Vol 522-523 ◽  
pp. 285-292 ◽  
Author(s):  
Hiroyuki Matsumaru ◽  
Shigenari Hayashi ◽  
Toshio Narita
Keyword(s):  
Diffusion Couple ◽  
Single Crystal ◽  
Diffusion Barrier ◽  
Alloy Layer ◽  
Quartz Ampoule ◽  
Diffusion Couples ◽  
Outward Diffusion ◽  
Barrier Coatings ◽  
Diffusion Treatment ◽  
And Diffusion

A diffusion couple study was carried out with Ni-based superalloy / γ’-Ni3Al with or without a Re-based alloy layer. The Re-based alloy containing Re, W, Cr, and Ni was formed on a second generation, single crystal Ni-based superalloy by using electroplating processes to form films of 70at%Re-Ni and Ni-20at%W, followed by Cr-pack cementation at 1573K for 36ks. The superalloy with or without the Re-based alloy layer was bonded to a γ’−Ni3Al alloy in vacuum. Diffusion couples were annealed in an evacuated quartz ampoule at 1423 K for 90 and 360ks. After the 360ks diffusion treatment the Re-based alloy remained sound and suppressed inward Al diffusion from the γ’-Ni3Al, it was further found that outward diffusion of alloying elements from the alloy substrate to the γ’-Ni3Al was also significantly reduced by the Re-based alloy layer.

scholarly journals Aluminide Thermal Barrier Coating for High Temperature Performance of MAR 247 Nickel Based Superalloy

Coatings ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 48
Author(s):  
Mateusz Kopec ◽  
Dominik Kukla ◽  
Xin Yuan ◽  
Wojciech Rejmer ◽  
Zbigniew L. Kowalewski ◽  
...  
Keyword(s):  
High Temperature ◽  
Stress Amplitude ◽  
Aluminide Coating ◽  
Chemical Vapor ◽  
Fatigue Tests ◽  
Protective Atmosphere ◽  
X Ray ◽  
Nickel Based Superalloy ◽  
Barrier Coating ◽  
Aluminide Layer

In this paper, mechanical properties of the as-received and aluminide layer coated MAR 247 nickel based superalloy were examined through creep and fatigue tests. The aluminide layer of 20 µm was obtained through the chemical vapor deposition (CVD) process in the hydrogen protective atmosphere for 8 h at the temperature of 1040 °C and internal pressure of 150 mbar. A microstructure of the layer was characterized using the scanning electron microscopy (SEM) and X-ray Energy Dispersive Spectroscopy (EDS). It was found that aluminide coating improve the high temperature fatigue performance of MAR247 nickel based superalloy at 900 °C significantly. The coated MAR 247 nickel based superalloy was characterized by the stress amplitude response ranging from 350 MPa to 520 MPa, which is twice as large as that for the uncoated alloy.

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