Cyclic high temperature corrosion studies of carbon nanotubes-Cr2O3composite coatings on boiler steel at 900°C in molten salt environment

2018 ◽  
Vol 65 (6) ◽  
pp. 646-657 ◽  
Author(s):  
Khushdeep Goyal ◽  
Hazoor Singh ◽  
Rakesh Bhatia
Keyword(s):  
Carbon Nanotubes ◽  
Corrosion Resistance ◽  
Weight Gain ◽  
High Temperature ◽  
Hot Corrosion ◽  
Corrosion Behaviour ◽  
Composite Coatings ◽  
High Temperature Corrosion ◽  
Content Type ◽  
Coating Matrix

PurposeMolten sulphate-vanadate induced hot corrosion is the main reason of failure of boiler tubes used at high temperatures in thermal power plants. The hot corrosion can be encountered by applying thermal spray coatings on the alloy steels. In this perspective, this paper aims to attempt to investigate the effect of carbon nanotubes reinforcement on Cr2O3composite coatings on hot corrosion behaviour of ASTM-SA213-T22 steel in a corrosive environment of Na2SO4– 60%V2O5at 900°C for 50 cycles.Design/methodology/approachThe coatings have been deposited with high velocity oxy fuel process. The samples were exposed to hot corrosion in a Silicon tube furnace at 900°C for 50 cycles. The kinetics of corrosion behaviour were analysed by the weight gain measurements after each cycle. Corrosion products were analysed with X-ray diffraction, scanning electron microscopy, energy dispersive and cross-sectional analysis techniques.FindingsDuring investigations, the carbon nanotubes (CNT) reinforced Cr2O3composite coatings on T22 steel were found to provide better corrosion resistance in the molten salt environment at 900°C. The coatings showed lower weight gain along with formation of protective oxide scales during the experiment. Improvement in protection against hot corrosion was observed with increase in CNT content in the coating matrix.Research limitations/implicationsThe addition of CNT has resulted in reduction in porosity by filling the voids in chromium oxide coating, with interlocking of particle and has blocked the penetration of corroding species to enhance the corrosion resistance of the composite coatings. The corrosion rate was found to be decreasing with increase in CNT content in coating matrix.Originality/valueIt must be mentioned here that high temperature corrosion behaviour of thermally sprayed CNT-Cr2O3composite coatings has never been studied, and it is not available in the literature. Hence, present investigation can provide valuable information for application of CNT-reinforced coatings in high temperature fuel combustion environments.

scholarly journals High-Temperature Corrosion Behaviour of HVOF Sprayed Cr3C2- 25NiCr Coated on Alloy X22CrMoV12-1 at 600o C

2018 ◽  
Vol 1 (1) ◽  
pp. 7-12
Author(s):  
P. Akshay Prasanna ◽  
◽  
P. Subramani ◽  
V. Sreenivasulu ◽  
N. Arivazhagan ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Molten Salt ◽  
Hot Corrosion ◽  
Corrosion Behaviour ◽  
High Temperature Corrosion ◽  
Spinel Oxide ◽  
Good Resistance ◽  
Good Corrosion Resistance ◽  
Temperature Environment

The present study investigates the hot corrosion behaviour of high-velocity oxy-fuel sprayed alloy X22CrMoV12-1 with Cr3C2-25NiCr coating at 600oC. The study was carried out by air and molten salt environment for both coated and uncoated substrates for 50 cycles. Thermogravimetry analysis was carried out to evaluate the hot corrosion by calculating the mass changes in each cycle. The results show that coating provides the marginally good corrosion resistance than the uncoated alloy. The formation of Fe2O3 and MoO3 phases in the uncoated substrates in both air and molten salt environments reduces the corrosion resistance at the high-temperature environment. The formation of Ni2Oand spinel oxide NiCr2O4 provided good resistance to corrosion in the coated substrates in the air and molten salt environment.

High temperature corrosion behaviour of aluminised FC 25 cast iron using pack cementation

2019 ◽  
Vol 66 (2) ◽  
pp. 236-241 ◽  
Author(s):  
Somrerk Chandra-Ambhorn ◽  
Neramit Krasaelom ◽  
Tummaporn Thublaor ◽  
Sirichai Leelachao
Keyword(s):  
Cast Iron ◽  
High Temperature ◽  
Corrosion Behaviour ◽  
Mass Gain ◽  
High Temperature Corrosion ◽  
Pack Cementation ◽  
X Ray Diffraction ◽  
Content Type ◽  
X Ray ◽  
Seat Insert

Purpose This study aims to apply the pack cementation to develop the Fe-Al layers on the surface of FC 25 cast iron in order to increase the high-temperature corrosion resistance of the alloy. Design/methodology/approach Pack cementation was applied on the surface of FC 25 cast iron at 1,050°C. The bare and aluminised alloys were subjected to the oxidation test in 20 per cent O2-N2 at 850 °C. Scanning electron microscopy equipped with energy-dispersive X-ray spectroscopy and X-ray diffraction (XRD) were used for characterisation. Findings The layers of pack cementation consisted of Fe2Al5, FeAl2 and FeAl, and solid solution alloyed with Al. The oxidation kinetics of the bare cast iron was parabolic. Mass gain of the aluminised cast iron was significantly decreased compared with that of the bare cast iron. This was because of the protective alumina formation on the aluminised alloy surface. Al in the Fe–Al layer also tended to be homogenised during oxidation. Originality/value Even though the aluminising of alloys was extensively studied, the application of that process to the FC 25 cast iron grade was originally developed in this work. The significantly reduced mass gain of the aluminised FC 25 cast iron makes the studied alloy be promising for the use as a valve seat insert in an agricultural single-cylinder four-stroke engine, which might be run by using a relatively cheaper fuel, i.e. LPG, but as a consequence requires the higher oxidation resistance of the engine parts.

Hot Corrosion Resistance Properties of Al-Si Coatings Obtained by Slurry Method

2012 ◽  
Vol 326-328 ◽  
pp. 273-278 ◽  
Author(s):  
Agnieszka Kochmańska
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Hot Corrosion ◽  
Protective Coatings ◽  
Cast Steel ◽  
High Temperature Corrosion ◽  
Air Atmosphere ◽  
Before And After ◽  
Slurry Method ◽  
Thermal Shocks

This paper presents the results of research on aluminide protective coatings manufactured on hightemperature creep resistant cast steel. The main purpose of these coatings is protection against the high temperature corrosion, at carburizing and oxidizing potential atmosphere. Coatings were obtained on cast steel type GXNiCrSi 3018 by slurry cementation in air atmosphere. The tests of carburizing and oxidizing were carried out. The structure of the coatings before and after carburizing and oxidizing is described in the present paper. The chemical composition, thickness and microstructure of coatings were determined. These coatings could protect equipment against hot corrosion at carburizing and oxidizing atmosphere and have thermal shocks resistance.

Characterization and hot corrosion behavior of D-gun sprayed Cr2O3-75% Al2O3 coated ASTM-SA210-A1 boiler steel in molten salt environment

2017 ◽  
Vol 64 (5) ◽  
pp. 515-528 ◽  
Author(s):  
Amita Rani ◽  
Niraj Bala ◽  
C.M. Gupta
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Molten Salt ◽  
Corrosion Behavior ◽  
Hot Corrosion ◽  
Degradation Mechanism ◽  
Effective Diffusion ◽  
Boiler Steel ◽  
Content Type ◽  
Scanning Electron

Purpose Hot corrosion is the major degradation mechanism of failure of boiler and gas turbine components. The present work aims to investigate the hot corrosion resistance of detonation gun sprayed (D-gun) Cr2O3-75 per cent Al2O3 ceramic coating on ASTM-SA210-A1 boiler steel. Design/methodology/approach The coating exhibits nearly uniform, adherent and dense microstructure with porosity less than 0.8 per cent. Thermogravimetry technique is used to study the high temperature hot corrosion behavior of bare and coated boiler steel in molten salt environment (Na2SO4-60 per cent V2O5) at high temperature 900°C for 50 cycles. The corrosion products are analyzed by using X-ray diffraction, scanning electron microscopy (SEM) and field emission scanning electron microscope/energy-dispersive analysis (EDAX) to reveal their microstructural and compositional features for elucidating the corrosion mechanisms. Findings During investigations, it was found that the Cr2O3-75 per cent Al2O3 coating on Grade A-1 boiler steel is found to be very effective in decreasing the corrosion rate in the molten salt environment at 900°C. The coating has shown lesser weight gains along with better adhesiveness of the oxide scales with the substrate till the end of the experiment. Thus, coatings serve as an effective diffusion barrier to preclude the diffusion of oxygen from the environment into the substrate boiler steel. Research limitations/implications Therefore, it is concluded that the better hot corrosion resistance of the coating is due to the formation of desirable microstructural features such as very low porosity, uniform fine grains and the flat splat structures in the coating; as compared to the bare substrate under cyclic conditions. Practical implications This research is useful for coal-fired boilers and other power plant boilers. Social implications This research is useful for power generation plants. Originality/value There is no reported literature on hot corrosion behavior of Cr2O3-75 per cent Al2O3 coating deposited on the selected substrates by D-gun spray technique. The present work has been focused to study the influence of the Cr2O3-75 per cent Al2O3 coating developed with D-gun spraying technique on high temperature corrosion behavior of ASTM-SA210-A-1 boiler steel in an aggressive environment of Na2SO4-60 per cent V2O5 molten salt at 900°C under cyclic conditions.

Optimization of pre-oxidation time for corrosion resistance of cobalt based coating alloy in mixed sulphates

2021 ◽  
Vol 68 (1) ◽  
pp. 29-35
Author(s):  
Abdul Rehman ◽  
Mohammad Hassan Shirani Bidabadi ◽  
Liang Yang ◽  
Zheng Yu ◽  
Chen Hao ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Hot Corrosion ◽  
Design Methodology ◽  
Corrosion Behaviour ◽  
Ambient Air ◽  
Oxidation Time ◽  
Oxidation Treatment ◽  
Content Type ◽  
Surface Oxides ◽  
Oxidation Effect

Purpose This study aims to optimise the effect of pre-oxidation on hot corrosion behaviour of Tribaloy T-900 at 900 °C in mixed Na2SO4 and K2SO4. Design/methodology/approach Prior to hot corrosion experiment, pre-oxidation treatments were carried in ambient air at 900 °C for 1, 5 and 10 h, respectively. The hot corrosion experiments were performed in a box type furnace at 900 °C. Both surfaces of specimens were brushed with saturated salt solution of 75 wt.% Na2SO4 + 25 wt.% K2SO4. After brushing, the salt-coated specimens were placed in electric stove to ensure drying of salt. After drying, presence of 3 mg/cm2 salt on specimen’s surface was ensured through weighting. Findings The 1-h pre-oxidation treatment prior to hot corrosion showed superior hot corrosion resistance against molten salt attack. An optimum pre-oxidation time of 1 h helped timely formation of protective Cr2O3 layer and inhibited the formation of less stable and porous surface oxides of Ni and Mo during hot corrosion. Originality/value Pre-oxidation effect on hot corrosion behaviour of refractory metal (such as Mo in investigated alloy) containing alloy has never been reported previously. Refractory metals oxide (e.g. MoO3) could transform the corrosion phenomena to catastrophic failure through acidic fluxing.

Corrosion Behaviour of Ti-48Al-2Nb-2Cr Alloys

2012 ◽  
Vol 323-325 ◽  
pp. 301-307
Author(s):  
B. Pelic ◽  
D. Rafaja ◽  
Patrick J. Masset ◽  
H.J. Seifert ◽  
L. Bortolotto ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
High Temperature ◽  
Elevated Temperatures ◽  
Protective Coatings ◽  
Corrosion Behaviour ◽  
Base Material ◽  
High Temperature Corrosion ◽  
Al Alloy ◽  
Environmental Embrittlement ◽  
Structural Applications

γ-TiAl intermetallics are attractive materials for high-temperature structural applications in the aerospace and automobile industries. However, they show environmental embrittlement at elevated temperatures that is mainly related to their low high-temperature corrosion resistance. One way how to improve the high-temperature corrosion resistance is the deposition of protective coatings on the surface of the base material. In this study, samples of a Ti-Al alloy with the chemical composition Ti-48Al-2Cr-2Nb (at.%) were covered by physically vapour deposited (PVD), by metalorganic chemically vapour deposited (MOCVD) and by high-velocity oxy-fuel (HVOF) sprayed coatings. All coatings were based on the Ti-Al alloys and contained different amounts of alloying elements. The corrosion experiments were performed in molten salts containing 75 wt.% Na2SO4and 25 wt.% NaCl at 850°C up to 336 h. Both, PVD and CVD protected coatings reduced the changes in the mass of the samples over the corrosion time. Still, the formation of TiO2could not be avoided, as it was confirmed by glancing-angle X-ray diffraction experiments.

Nanocrystalline, Enamel and Composite Coatings for Superalloys

2018 ◽  
pp. 160-186
Author(s):  
Shenglong Zhu ◽  
Fuhui Wang
Keyword(s):  
Thermal Expansion ◽  
Corrosion Resistance ◽  
High Temperature ◽  
Thermophysical Properties ◽  
Hot Corrosion ◽  
Composite Coatings ◽  
Thermally Grown Oxide ◽  
Nanocomposite Coatings ◽  
Thermally Grown

This chapter describes several innovations for improving the performance of high-temperature coatings. Nanocrystallization has been demonstrated to be a practical way to prolong the lifetime of high temperature coatings by decreasing the minimum Al concentration for sustaining the growth of thermally grown oxide (TGO) scales, and increasing the resistance against scale cracks and spallation. Enamel coatings with enhanced strength, toughness and thermophysical properties were developed for improving the hot corrosion resistance of superalloys. Low expansion nanocomposite coatings minimize the mismatch between coefficients of thermal expansion (CTEs) of the TGO scales and the underlying coatings, so allow growth of thicker TGO scales free of cracks and spallation and then prolong the lifetime.

High temperature corrosion behaviour of a gradient NiCoCrAlYSi coating II: Oxidation and hot corrosion

2010 ◽  
Vol 52 (7) ◽  
pp. 2316-2322 ◽  
Author(s):  
S.M. Jiang ◽  
H.Q. Li ◽  
J. Ma ◽  
C.Z. Xu ◽  
J. Gong ◽  
...  
Keyword(s):  
High Temperature ◽  
Hot Corrosion ◽  
Corrosion Behaviour ◽  
High Temperature Corrosion

scholarly journals HOT CORROSION BEHAVIOUR OF NICKEL BASED SUPERALLOYS

2013 ◽  
pp. 223-227
Author(s):  
K. SRINIVASA VADAYAR ◽  
S. DEVAKI RANI
Keyword(s):  
High Temperature ◽  
Surface Morphology ◽  
Hot Corrosion ◽  
Corrosion Behaviour ◽  
Degradation Mechanism ◽  
Sem Analysis ◽  
High Temperature Corrosion ◽  
Corrosive Environment ◽  
Weight Changes ◽  
Electron Dispersive Spectroscopy

High temperature corrosion of coated and uncoated IN738LC and uncoated CM247LC nickel based super alloys in chloride and vanadium environment were carried out. To create corrosive environment (i.e. chloride and vanadium environment) salts of required proportions of Na2SO4, NaCl and V2O5 were applied on both sides of samples and loaded into the furnace at 700°C and 900°C. The weight changes were noted and SEM analysis was done to determine the surface morphology of hot corroded samples. Electron Dispersive Spectroscopy (EDS) was used to determine different elements present in corroded samples of CM247LC and IN738LC in chloride and vanadium environments at 700°C and 900°C. The present study revealed that CM247LC is more susceptible to hot corrosion than IN738LC due to varying amount of chromium and tungsten which is explained by degradation mechanism. Coated IN738LC has more life span than that of other samples.

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