Boiler Steel Research Articles

Material volume reduction for creep testing using composite cantilevers and its application for residual life assessment

Digital image correlation (DIC) and finite element analysis (FEA) demonstrate that creep deformation in bending occurs primarily in ≈30 % of the cantilever volume near the fixed end, especially when the creep stress exponent ranges from 5 to 7. As an alternative approach to minimize the material volume required for testing, the concept of fabricating composite cantilevers is proposed and validated in this study. A composite cantilever sample consists of an “active” creeping portion (e.g., T22 boiler steel) and an additively extended “passive” non-creeping portion (e.g., IN718). The volume reduction process involved varying the length of the “active” section, a, while keeping the total length of the cantilever, L, constant. The DIC measurements conducted at 600 °C to assess the creep behavior of T22 steel revealed that analytical expressions for monolithic cantilevers could aptly predict the constitutive steady-state creep laws from the composite cantilevers if measurements are made in a region at a critical distance away from the interface. FEA indicates that accurate stress estimation enables predicting monolithic creep behavior using composite samples with “a/L” ratios of as small as 5 %. Using the developed approach, the loss of creep resistance of T11 boiler steel that was in service for ∼ 240,000 h was ascertained in high throughput fashion using a composite cantilever having only 30 vol % of the “active” material. Guidelines to minimize the volume fraction of the “active” portion in the composite cantilever and the implications of the observations for estimating the residual life of in-service high-temperature components are discussed.

Hot Corrosion Performance Analysis of Microwave Heat-Treated Al2O3-Based Coatings Deposited on SA 210 Grade-I Boiler Steels

Hot Corrosion Performance Analysis of Microwave Heat-Treated Al2O3-Based Coatings Deposited on SA 210 Grade-I Boiler Steels

Assessment of the microstructure, adhesion and elevated temperature erosion resistance of plasma-sprayed NiCrAlY/cr3C2/h-bn composite coating

This study uses an air jet erosion tester to investigate the erosion behavior of NiCrAlY/Cr3C2/h-BN composite coatings that are plasma-sprayed at three different temperatures and 40 m/s on T22 boiler steel alloy. 30 and 90° are the impingement angles. To identify the erosion mechanism, SEM and X-ray diffraction techniques are used to analyze the surface morphology and phase generated on the eroded surface. Findings of erosion test indicate that the erosion resistance was notably enhanced by addition of Cr3C2 and h-BN because of its lubricating characteristics and capacity to reduce frictional forces during erosion. The combined influence of Cr3C2 and h-BN enhanced the coating hardness and erosion wear resistance, thereby improving its overall resistance to erosion. The weight loss method was employed to calculate the erosion rate, and the NiCrAlY/Cr3C2/h-BN coating showed up to 30.55% and 34.48% lower erosion rate as compared to uncoated T22 substrate at 600 °C for 30° and 90° impact angles, respectively. This characteristic is affected by the hard reinforcement Cr3C2's high-temperature stability, the h-BN's self-lubricating ability, the formation of a protective oxide layer that forms at 600 °C, and the eroded coating's ductile behavior of material removal. The study also reveals that the NiCrAlY/Cr3C2/h-BN coating system on T22 boiler steel alloy has excellent erosion resistance, making it suitable for use in high-temperature and erosive environments in boiler systems and similar industries.

High temperature oxidation mitigation efficacy of Al2O3 and Ni-20Cr ceramic coating on boiler steel application

The primary reason of degradation and failure of many products used for high temperature applications are oxidation. Protective coatings are employed to increase the component resistance to oxidation. In the present research work, Al2O3 and Ni-20Cr were applied as coatings on SAE431 steel using a detonation gun spraying technique. At 800 °C in air with 50 cycles of heating and cooling, the oxidation behavior of uncoated and coated SAE-431 boiler steel was analyzed. Ni-20Cr coating on SAE431 boiler steel exhibits approximately 25.44 % higher oxidation resistance and the Al2O3 coating on SAE431 boiler steel exhibits approximately 32.22 % higher oxidation resistance compared to uncoated SAE431 boiler steel. After oxidation at 800 °C, the SAE431 boiler steel coated with Ni-20Cr displays prominent peaks of the Cr2O3 and Ni phases, with some minor phase of NiO. The NiO phase is observed to be less intense than Cr2O3 and Ni phases. After oxidation at 800 °C, Al2O3 coated SAE431 boiler steel exhibited strong peaks of ƞ-Al2O3 and δ-Al2O3 phases. The X-ray diffraction investigation also reveals the existence of the α-Al2O3 phase. According to our findings, based on weight change data, Ni-20Cr and Al2O3 coated boiler steel provided higher oxidation resistance than the uncoated SAE431boiler steels. The enhancement in the oxidation resistance of boiler steel can be attributed to the formation of nickel, chromium and aluminum oxide inert layer which is evident from the XRD patterns also. Exploration throughout global survey has been already done and it was found that not much work has been done on the high-temperature behavior of Ni-20Cr and Al2O3 coatings. The data obtained from the study will be helpful in examining the viability of using these coatings on boiler tubes.

Characterization Evaluation of Plasma-Sprayed CNT Reinforced Inconel718 Coatings on T91 Boiler Steels

Characterization Evaluation of Plasma-Sprayed CNT Reinforced Inconel718 Coatings on T91 Boiler Steels

Comparison on erosion performance of HVOF sprayed NiCrSiBCFe-WC-Co and NiCrSiBCFe-Cr3C2NiCr coatings

Hard coatings are used to improve the wear resistance of various engineering materials while maintaining the mechanical properties of the base material. In this work, the high-velocity oxy-fuel (HVOF) thermal spray process was used to deposit NiCrSiBCFe(65)-WC-Co(35) and NiCrSiBCFe(65)-Cr3C2-NiCr(35) coatings on SA213-T17 boiler steel to improve the erosion wear resistance of the base material. The erosion wear behaviours of the specimens were investigated using an air jet erosion tester at 30 and 90° impact angles and 400 ± 25 °C temperature. The surface morphologies of the as-deposited and eroded samples were examined using the Scanning electron microscope. The NiCrSiBCFe-WC-Co ceramic coating deposited on SA213-T17 boiler steel exhibited superior erosion resistance compared to NiCrSiBCFe-Cr3C2-NiCr coating and boiler steel under all the tested conditions. This enhanced performance can primarily be attributed to the higher hardness of the NiCrSiBCFe-WC-Co coating due to the presence of harder phases such as WC, W2C and NiCo2O4.

Investigation of Cyclic Oxidation and Hot Corrosion Behaviour of Plasma-Sprayed NiCrAlY/Cr3C2/h-BN/Mo Coatings on T22 Boiler Steel Alloy

Investigation of Cyclic Oxidation and Hot Corrosion Behaviour of Plasma-Sprayed NiCrAlY/Cr3C2/h-BN/Mo Coatings on T22 Boiler Steel Alloy

Slurry sprayed glass-ceramic coating for boiler tubes and its high temperature performance

Industrial boilers operate in extreme environments and are prone to degradation caused by high temperature oxidation, corrosion, and erosion. Protective coatings provide boiler components with protection to prolong their operation lifetime. Thus, a glass-ceramic coating has been developed using a slurry spray technique on carbon steel AS/NZS 3678 substrates. Microstructure, mechanical characteristics, and high temperature performance of the coating were investigated. The coating composed of chemically inert oxide ceramics dispersed in a glassy silicate binder matrix. The adhesion strength of the coating was 10.79 ± 0.86 MPa. Coating mass loss after abrasion test was 0.013 % of the tested specimen. The coating withstood at least 75 air quenched thermal shock cycles from 800 °C to the room temperature without any visible spallation and cracks. The coating mostly remained undamaged after cyclic oxidation at 800 °C for 10 cycles. However, minor iron oxide formation was observed, specifically, in relatively thin sections of the coating. The oxidation resistance of the boiler steel has been improved with the developed coating. The linear oxidation rate constant of the boiler steel has been statistically reduced from 6.90 × 10−4 mg cm−2 s−1 to 1.95 × 10−4 mg cm−2 s−1 for coated steel (p = 0.007). The developed slurry spray glass-ceramic coating is a potential candidate for boiler environments.

Role of Carbide-Based Thermal-Sprayed Coatings to Prevent Failure for Boiler Steels: A Review

Role of Carbide-Based Thermal-Sprayed Coatings to Prevent Failure for Boiler Steels: A Review

Thermal spray coatings on high-temperature oxidation and corrosion applications – A comprehensive review

In high-temperature boiler operations, conventional steels and alloys grapple with the formidable challenges posed by oxidation and corrosion. Prolonged exposure to extreme thermal conditions exacerbates these issues, progressively diminishing operational efficiency. Surface treatment emerges as a pivotal strategy for safeguarding materials against deterioration while optimizing component performance cost-effectively. Recent attention has honed on surface coatings as a means to combat hot corrosion in boiler steels. Thermal coating, electroplating, and other metallurgical techniques are widely embraced for surface modification, with composite coatings gaining traction for bolstering metallurgical, mechanical, and corrosion resistance properties. This review, unlike any other, takes a comprehensive approach to exploring various thermal spraying methods and their applications, ensuring a robust understanding of the subject matter. Beyond a mere compilation of existing literature, this review identifies emerging trends and technologies, offering fresh insights and interpretations. In this work, 84 articles were critically evaluated for current research, discerning strengths, weaknesses, and avenues for future research on thermal spray coatings on high-temperature oxidation and corrosion. This incisive approach promises to enrich the knowledge base of researchers, scholars, and professionals in materials science, metallurgy, and industrial engineering, facilitating advancements in the field. By pinpointing research gaps in thermal spray coating, this study directs attention toward areas ripe for further investigation, fostering continued innovation and progress.

Thermodynamic Analysis of Chloride Corrosion in Steel for Energy System Applications in Fe-O-Cl-Na Environments

The assumptions of contemporary energy policies are increasing the share of renewable energy sources. Biomass combustion is developing as an alternative to fossil fuels. However, it faces challenges such as limited corrosion resistance of steel boiler components due to chloride compounds in flue gases and fly ash. This paper provides a comprehensive thermodynamic analysis of chloride-induced corrosion in steel in the Fe-O-Cl-Na environment, focusing on the influence of steam concentration in the gas phase. The study was performed by using the general thermodynamic rules, the thermodynamic properties of the pure components involved in the reaction, and the properties of the solutions formed in the liquid and gas phases. The study also examined the impact of alkali metal chlorides, particularly NaCl, on the formation of NaFeO2 in the passive oxide scale layer Fe3O4/Fe2O3. Furthermore, it investigated the condensation of NaCl vapour formation of low-melting eutectic mixtures in deposits and the resulting consequences on the corrosion process. The role of HCl in the chlorination and oxidation process of steel in melted ash deposits was also discussed. The presented thermodynamic analysis was compared with assumptions of an “active oxidation” model. This study can be a valuable resource for experimental research planning and a guide for preventing corrosion in industrial settings.

Microstructural characterization and electrochemical behaviour of HVOF sprayed WC-Co-Cr coatings on 316L boiler steel stainless steel

Corrosion is the gradual erosion of metal, primarily because of electrochemical attacks especially under gaseous and alkaline conditions owing to the presence of sulphur and Alkali metals may cause rapid material degradation called Hot corrosion and result in untimely failure of components. To improve surface qualities for corrosion applications, the austenitic 316L stainless steel (SS) in this study was coated with Wc-10%Co–4%Cr utilizing the High-velocity oxy-fuel (HVOF) spray method. After the coated sample was heated to 800 °C for an hour, XRD was used to confirm the coating powder's composition. Using the FESEM technique, the microstructure features were examined, and XRD analysis was performed to ascertain the phase and composition of the substrate. Investigations were also conducted on the electrochemical corrosion characteristics that were impacted by the heat treatment after coating. SEM and EDAX technologies were used to characterize the sample and study its microstructure.

Enhancing Resistance to Corrosion, Erosion and Oxidation of Boiler Steels by Surface Modification Techniques

In coal based thermal power plant, the boiler components (superheater, combustion chamber, superheater tubes, boiler walls, reheater etc.) are subjected to harsh environment characterized by high temperatures, aggressive combustion products, and abrasive particles. Corrosion, erosion, and oxidation relentlessly reduce their lifespan and efficiency, posing significant economic and safety concerns. This review explores the potential of surface modification techniques to act as a valiant shield against these destructive forces, extending the life, enhancing the performance, and ensuring the safe operation of boiler components. In this articles various surface modifications techniques including their merits and demerits are discussed with emphasis on thermal spray techniques. From established methods like thermal spraying and laser cladding to innovative approaches like nanocoatings and electrochemical treatments, each technique is meticulously examined for its effectiveness in boosting corrosion resistance, mitigating erosion wear, and minimizing oxidation at crucial boiler locations. This review culminates in a compelling vision of the future, where sophisticated surface modification techniques become an integral part of boiler design and maintenance strategies. By harnessing the power of these technologies, we can usher in an era of more efficient, reliable, and sustainable boiler operation, safeguarding investments and protecting the environment.

Experimental investigation on the high-temperature corrosion of 12Cr1MoVG boiler steel in waste-to-energy plants: Effects of superheater operating temperature and moisture

Waste-to-energy (WTE) technology via municipal solid waste incineration (MSWI) have developed very rapidly with the advantages of achievement on waste disposal and energy conversion. This technology is developing towards higher capacity and efficiency. Therefore, the operation parameters of WTE boilers must be improved. However, higher steam parameters means higher surface temperature of exchange tube in superheaters and reheaters in WTE boilers, resulting higher risk of engineering failure due to high-temperature corrosion. Additionally, the incineration of MSW releases flue gas with a high content of corrosive species and water vapor, which can cause severe high-temperature corrosion. This experimental investigation details the effect of surface temperature and water vapor concentration on the high-temperature corrosion behavior of 12Cr1MoVG boiler steel under an atmosphere mimicking MSWI. The corrosion test environment consists of high temperature, ash deposit and simulated flue gas of waste incineration according to a real WTE boiler. The experiment was conducted using a two-zone bench-scale tube furnace with a gas temperature of 600℃ and the sample temperatures of 380℃, 430℃, and 480℃. For the investigation of water vapor concentration effect, 18 % vol and 23 % vol were set up in this study. After 240 hours of exposure, the corrosion weight curves illustrated that the corrosion kinetics was highly dependent on the surface temperature of corrosion samples. Furthermore, an increase in water vapor concentration exacerbated the high-temperature corrosion. XRD analysis identified the corrosion products as metal chlorides and metal oxides. Cross-sectional SEM images and EDS analysis revealed that an increase in water vapor accelerated the corrosion rate of the steel samples due to chromium dilution behavior.

Comparative erosion performance of HVOF and LVOF sprayed NiCrSiBCFe-WC-Co coating

Thermal spray coatings enhance one or more surface properties of engineering components. In this work, NiCrSiBCFe-WC-Co composite coating powder is deposited over SA213-T12 boiler steel using the high velocity oxy fuel spraying (HVOF) and low velocity oxy fuel spraying (LVOF) thermal spray methods to improve erosion performance. XRD and scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS) were used to examine the surfaces and constituents of as-deposited specimens, whereas SEM was used to investigate the eroded specimens. The erosion behaviours of developed coatings were investigated at 30° and 90° impact angles, 53 m/s and 400°C. XRD analysis of the HVOF coating showed an additional peaks of NiCo2O4, SiC and Ni2B with common peaks Ni, WC, W2C, Cr23C6 and C6(Cr,Co,Ni)23 to that of LVOF coating. HVOF-sprayed coating demonstrated higher microhardness and adhesion strength with lower porosity than LVOF-sprayed coating. The HVOF-sprayed NiCrSiBCFe-WC-Co coating demonstrated comparatively better erosion resistance than LVOF-sprayed NiCrSiBCFe-WC-Co coating, attributed to its superior properties. The mechanism of erosion, concerning the different characteristics of the coatings, is discussed.

Influence of post-welding heat treatment on microstructure and peculiarity of 10Cr9Mo1VNb boiler steel welded by hot wire TIG

Hot wire tungsten noble gas (HW-TIG) soldering tests are conducted on 10Cr9Mo1VNb boiler steel with multi-layer and multi-pass, and the soldered joints are subjected to post-weld heat treatment (PWHT) at different temperatures and times from 740°C to 790°C and 1 hour to 4 hours. The influence of PWHT on the microstructure and peculiarity of the joints are analyzed by using hardness, metallography, room temperature tensile testing, Charpy impact testing, SEM, and other experimental methods. The results show that the PWHT can transform the martensite formed in the welding process into tempered martensite, which can significantly improve the uniformity of the microstructure and peculiarity of each area of the joint. When subjected to heat treatment at 740°C, both strength and ductility improve with the increase of heat treatment time, while the plasticity gets a slight decrease. However, when subjected to heat treatment at 790°C, strength, plasticity, and ductility decrease with the increase of time, mainly due to the carbide coarsening such as M23C6 in the joint.

Failure analysis of steam superheater boiler tube made of ASTM T22 steel

This study investigates the failure of T22 grade steel boiler tube, as per ASTM A 213/A A213M standards, which experienced significant plastic deformation with a characteristic 'fish mouth' appearance. Analysis revealed an increase in outer diameter up to 18 percent, coupled with a reduction in wall thickness from 8.8 mm to around 3 mm at the rupture site. Microstructural examination of samples taken away from the rupture site revealed a structure composed of ferrite and partially decomposed bainite, attributed to prolonged annealing, along with fine spherical carbide precipitates. Samples from the rupture area displayed ferritic-bainitic structure without secondary carbide precipitates, indicating exceeded transformation temperatures. Additionally, increased hardness in the rupture area suggested transitions of overcooled austenite into ferrite and bainite. Thickened scale, particularly on the inner surface, heightened the risk of overheating. Based on these findings, it was concluded that the tube failure resulted from short-time overheating.

Steel Boiler Tube with HVOF Coating: Peculiarity and Interfacial

In this research, a NiCrMoFeCoAl-30%Cr3C2 composite finish was deposited using an HVOF technique on the T22 bare steel. Cr3C2 coatings provide excellent durability and corrosion resistance. When manufacturing homogenous and dense Cr3C2 layers with decreased as-deposited greater hardness, surface roughness, and enhanced quality corrosion resistance, high-velocity oxy-fuel spraying with suspension feedstock has been a viable choice. Scanning electron microscopy with energy dispersive spectroscopy and X-ray diffraction have been used to examine the specimen's microstructure. Coating properties such as thickness, microhardness, and porosity were measured.

Effect of Superficially Applied MnO2 and Al2O3 Oxide Inhibitors in Enhancing High-Temperature Corrosion of T22 Boiler Steel

Effect of Superficially Applied MnO2 and Al2O3 Oxide Inhibitors in Enhancing High-Temperature Corrosion of T22 Boiler Steel

Review of Thermal Spray Coatings Perform in Protecting Boiler Steels Against Corrosion at High Temperatures

Failure of boilers can cause huge economic loss to the power plants. In high temperature and aggressive working conditions erosion, hot corrosion and abrasions are most responsible factors for failure of boiler steels. Thermal spray coatings are the preferable method to minimize the cause of failures of the boiler steels due to these problems. Among different thermal spray techniques. By utilizing the HVOF process, it is possible to produce coatings with high micro-hardness and low porosity, making it an advanced and effective method that is currently undergoing rapid development. In this paper a review study regarding the performance of thermal spray coatings deposited on boiler steels against the hot corrosion has been presented. The outcomes of this research have the potential to assist in identifying the optimal coating combination and application technique to prevent the deterioration of boiler steels.