High-Temperature Oxidation Resistance of PDC Coatings in Synthetic Air and Water Vapor Atmospheres

This work is aimed at the development and investigation of the oxidation behavior of ferritic stainless-steel grade AISI 441 and polymer-derived ceramic (PDC) protective coatings. Double-layer coatings of a PDC bond coat below a PDC top coat with glass and ceramic passive fillers’ oxidative resistance were studied at temperatures up to 1000 °C in a flow-through atmosphere of synthetic air and in air saturated with water vapor. Investigation of the oxide products formed at the surface of the samples in synthetic air and water vapor atmospheres, at different temperatures (900, 950, 1000 °C) and exposure times (24, 96 h) was carried out on both uncoated steel and steel coated with selected coatings by scanning electron microscopy (SEM) and X-Ray diffraction (XRD). The Fe, Cr2O3, TiO2, and spinel (Mn,Cr)3O4 phases were identified by XRD on oxidized steel substrates in both atmospheres. In the cases of the coated samples, m- ZrO2, c- ZrO2, YAG, and crystalline phases (Ba(AlSiO4)2–hexacelsian, celsian) were identified. Scratch tests performed on both coating compositions revealed strong adhesion after pyrolysis as well as after oxidation tests in both atmospheres. After testing in the water vapor atmosphere, Cr ions diffused through the bond coat, but no delamination of the coatings was observed.

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PDC Glass/Ceramic Coatings Applied to Differently Pretreated AISI441 Stainless Steel Substrates

Materials ◽

10.3390/ma13030629 ◽

2020 ◽

Vol 13 (3) ◽

pp. 629 ◽

Cited By ~ 2

Author(s):

Milan Parchovianský ◽

Ivana Parchovianská ◽

Peter Švančárek ◽

Günter Motz ◽

Dušan Galusek

Keyword(s):

Stainless Steel ◽

Bond Coat ◽

Steel Substrate ◽

Composite Coatings ◽

Spray Coating ◽

Ceramic Coatings ◽

Strong Adhesion ◽

Cleaning Procedures ◽

Small Cracks ◽

Steel Substrates

In this work, the influence of different cleaning procedures on adhesion of composite coatings containing passive ceramic and commercial glasses was investigated. Two compositions (C2c, D2-PP) of double-layer polymer-derived ceramic (PDC) coating systems, composed from bond coat and a top coat, were developed. In order to obtain adherent coatings, stainless steel substrates were cleaned by four different cleaning procedures. The coatings were then deposited onto the steel substrate via spray coating. Pretreatment by subsequent ultrasonic cleaning in acetone, ethanol and deionised water (procedure U) was found to be the most effective, and the resultant C2c and D2-PP coatings, pyrolysed at 850 °C, indicated strong adhesion without delamination or cracks, propagating at the interface steel/bond coat. In the substrate treated by sandblasting and chemical etching, small cracks in the bond coat were observed under the same pyrolysis conditions. After oxidation tests, all coatings, except for those subjected to the U-treated substrates, showed significant cracking in the bond coat. The D2-PP coatings were denser than C2c, indicating better protection of the substrate.

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Oxidation Resistance and Microstructure Evaluation of a Polymer Derived Ceramic (PDC) Composite Coating Applied onto Sintered Steel

Materials ◽

10.3390/ma12060914 ◽

2019 ◽

Vol 12 (6) ◽

pp. 914 ◽

Cited By ~ 2

Author(s):

Tercius Justus ◽

Priscila Gonçalves ◽

Martin Seifert ◽

Mateus Leite ◽

Sônia Probst ◽

...

Keyword(s):

Oxidation Resistance ◽

Defect Formation ◽

Protective Coatings ◽

Mass Gain ◽

Silicon Carbonitride ◽

Sintered Steel ◽

Different Temperatures ◽

Near Net Shape ◽

Glass Fillers ◽

Steel Substrates

Powder metallurgy is a competitive technology to produce ferrous near net shape parts for diverse engineering applications. However, their inherent porosity increases the susceptibility to oxidation and sealing their surface is mandatory to avoid premature degradation. Alongside, polymer derived ceramics (PDCs), such as silicon-carbonitride, have drawn attention concerning their high temperature and chemical stability. However, PDCs undergo volume shrinkage during ceramization that leads to defect formation. The shrinkage can be compensated by the addition of fillers, which are also capable of tailoring the ceramic resulting properties. This work evaluates the processing of PDC-based coatings loaded with ZrO2 and glass fillers to compensate for the shrinkage, densify the coating and seal the sintered steel surface. Therefore, polymeric slurries were sprayed onto sintered steel substrates, which were pyrolyzed at different temperatures for microstructural and oxidation resistance evaluation. Microstructural modifications caused by the enhanced glass viscous flow during pyrolysis at 800 °C resulted in more homogeneous, dense and protective coatings, which reduced the mass gain up to 40 wt% after 100 h of oxidation at 450 °C in air in comparison to the uncoated substrate. Moreover, no macrocracks or spallation were detected, confirming the feasibility of PDC composite barrier coatings for sintered steels.

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In-situ NiO nanostructure growth during heating in water vapor atmosphere

Microscopy and Microanalysis ◽

10.1017/s1431927621007595 ◽

2021 ◽

Vol 27 (S1) ◽

pp. 2102-2103

Author(s):

Boyi Qu ◽

Klaus van Benthem

Keyword(s):

Water Vapor ◽

Water Vapor Atmosphere

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Oxidation Behavior of Maraging 300 Alloy Exposed to Nitrogen/Water Vapor Atmosphere at 500 °C

Metals ◽

10.3390/met11071021 ◽

2021 ◽

Vol 11 (7) ◽

pp. 1021

Author(s):

Mauro Andres Cerra Florez ◽

Gemma Fargas Ribas ◽

Jorge Luiz Cardoso ◽

Antonio Manuel Mateo García ◽

Joan Josep Roa Rovira ◽

...

Keyword(s):

Water Vapor ◽

Oxide Layer ◽

Magnetic Layer ◽

Adhesive Force ◽

Point Of View ◽

Maraging Steels ◽

Cobalt Spinel ◽

Water Vapor Atmosphere ◽

Iron Nickel ◽

Ferrite Cobalt

Aging heat treatments in maraging steels are fundamental to achieve the excellent mechanical properties required in several industries, i.e., nuclear, automotive, etc. In this research, samples of maraging 300 alloy were aged using a novel procedure that combines different steps with two atmospheres (nitrogen and water vapor) for several hours. The oxidized surface layer was chemical, microstructural and micromechanically characterized. Due to the thermodynamic and kinetic conditions, these gases reacted and change the surface chemistry of this steel producing a thin iron-based oxide layer of a homogeneous thickness of around 500 nm. Within the aforementioned information, porosity and other microstructural defects showed a non-homogeneous oxide, mainly constituted by magnetite, nickel ferrite, cobalt ferrite, and a small amount of hematite in the more external parts of the oxide layer. In this sense, from a chemical point of view, the heat treatment under specific atmosphere allows to induce a thin magnetic layer in a mixture of iron, nickel, and cobalt spinel ferrites. On the other hand, the oxide layer presents an adhesive force 99 mN value that shows the capability for being used for tribological applications under sliding contact tests.

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Evaluation of Li mass loss from Li2TiO3 with excess Li pebbles in water vapor atmosphere

Fusion Engineering and Design ◽

10.1016/j.fusengdes.2018.02.032 ◽

2018 ◽

Vol 136 ◽

pp. 362-366 ◽

Cited By ~ 2

Author(s):

Kazunari Katayama ◽

Haruaki Sakagawa ◽

Tsuyoshi Hoshino ◽

Satoshi Fukada

Keyword(s):

Water Vapor ◽

Mass Loss ◽

Water Vapor Atmosphere

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Improving Tribological Characteristics of Hip Prostheses Using Biocompatible Nanocoatings

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.741.67 ◽

2013 ◽

Vol 741 ◽

pp. 67-72 ◽

Cited By ~ 3

Author(s):

Gheorghe I. Gheorghe ◽

Liliana Laura Badita

Keyword(s):

Hip Prosthesis ◽

Protective Coatings ◽

Scratch Resistance ◽

Hip Prostheses ◽

Force Microscopy ◽

Tin Coatings ◽

Femoral Heads ◽

Before And After ◽

Tin Thin Films ◽

Steel Substrates

Total hip prosthesis (THP) is the most success of the 20th century in orthopaedic biomedical engineering. However due to difficult conditions within the human body its durability is generally limited to 15-16 years. THP is a bio-tribosystem, on which many mechanical, thermal, chemical and biological factors act. This paper presents the results of an analysis regarding the topography and tribological parameters of femoral heads structures before and after TiN coating. We report on the synthesis of TiN thin films on steel substrates by pulsed laser deposition (PLD) method for improving the mechanical characteristics of the structures. Adhesion resistance of the coating on the sub-layer was evaluated by scratching tests accompanied by Optical Microscopy (OM), Atomic Force Microscopy (AFM) and Scanning Electron Microscopy (SEM). As a principal result, this work points out that TiN protective coatings deposited by PLD technique with the maximum number of pulses can represent an alternative technology to ensure adhesion and scratch resistance of TiN coatings on femoral heads.

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A Multiscale NDT System for Damage Detection in Thermal Barrier Coatings

Volume 11: Mechanics of Solids, Structures and Fluids ◽

10.1115/imece2009-10694 ◽

2009 ◽

Author(s):

A. M. G. Luz ◽

D. Balint ◽

K. Nikbin

Keyword(s):

High Temperature ◽

Damage Detection ◽

Luminescence Spectrum ◽

Bond Coat ◽

Gas Turbines ◽

Thermal Stresses ◽

Assessment Tool ◽

Diagnostic Tools ◽

Spectral Parameters ◽

Temperature Oxidation

Progress in aero-engines and land-based gas turbines is continuously linked with a rise of the operating temperature. TBCs are multilayered structures which function together to effectively lower the temperature of its load-bearing superalloy substrate while simultaneously providing oxidation protection against high temperature combustion environments during operation. They typically comprise of a ceramic top coat for thermal insulation and a metallic bond coat that provides oxidation/corrosion resistance and enhances the adhesion of the YSZ to the superalloy substrate. Due to high-temperature oxidation of the bond coat, a thermally grown oxide (TGO) scale of continuous Al2O3 is formed between the ceramic top coat and the bond coat. The formation and growth of the TGO increases the mismatch of thermal expansion coefficients among the multilayered TBC and induce high thermal stresses leading to spallation of the YSZ coat from the underlying metal. Hence, nondestructive diagnostic tools that could reliably probe the subsurface damage state of TBCs are essential to take full advantage of these systems. In this contribution, a new concept of multiscale NDT system is presented. The instrument uses a combination of imaging-based methods with photoluminescence piezospectroscopy, a laser-based method. Imaging-based methods like mid-infrared reflectance, laser optical backscatter and infrared tomography were used to predict the overall lifetime of the coated component. When TBCs approach the end of life, micro-crack nucleation and propagation at the top coat/bond coat interface increases the amount of reflected light. This rise in reflectance was correlated with the lifetime of the component using a neural network that merges the mean and standard deviation value of the gray level. Photoluminescence piezospectroscopy was subsequently used to give information about the structural integrity of the hot spots identified in the image analysis. This laser-based technique measures in-situ the residual stress in the TGO at room temperature. Damage leads to a relaxation of the local stress which is in turn reflected in the luminescence spectrum shape. However, presently there is no agreement on the best spectral parameters that should be used as a measure of the damage accumulation in the coatings. Therefore, the evolution of luminescence spectrum from as-manufactured to critically damaged TBCs was determined using the finite element method. This approach helped to identify the most suitable spectral parameters for damage detection, improving the reliability of photoluminescence piezospectroscopy as a failure assessment tool for TBCs.

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Laser Sintering of Nano-Al2O3 Powders on Plasma Sprayed Ceramic Based Coatings

First International Conference on Integration and Commercialization of Micro and Nanosystems, Parts A and B ◽

10.1115/mnc2007-21215 ◽

2007 ◽

Author(s):

Lida Shen ◽

Yinhui Huang ◽

Zongjun Tian ◽

Guoran Hua

Keyword(s):

Wear Resistance ◽

Corrosion Resistance ◽

Plasma Spraying ◽

Bond Coat ◽

Continuous Wave ◽

Ceramic Coatings ◽

Laser Sintering ◽

Al2o3 Ceramic ◽

Plasma Sprayed ◽

Steel Substrates

This paper describes an investigation of nano-Al2O3 powders reinforced ceramic coatings, which has included NiCrAl and Al2O3+13%wt.TiO2 coats pre-produced by atmosphere plasma spraying, implemented by laser sintering. Commercial NiCrAl powders were plasma sprayed onto 45 Steel substrates to give a bond coat with thickness of ∼100μm. The 600μm thick Al2O3+13%wt.TiO2 based coating was also plasma sprayed on top of the NiCrAl bond coat. With 2.5kw continuous wave CO2 laser, nano-Al2O3 ceramic powders were laser sintered on the based Coatings. The micro structure and chemical composition of the modified Al2O3+13%wt.TiO2 coatings were analyzed by such detection devices as scanning electronic microscope (SEM) and x-ray diffraction (XRD). Microhardness, wear resistance and corrosion resistance of the modified coatings were also tested and compared with that of the unmodified. The results show that the crystal grain size of Al2O3 had no obvious growth. In addition, due to the nanostructured Al2O3 ceramic phases, the coatings exhibited higher microhardness, better wear resistance and corrosion resistance than those unmodified counterparts. The complex process of plasma spraying with laser sintering as a potential effective way of the application of ceramic nano materials was also simply discussed and summarized in the end.

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