Detonation Gun Research Articles

Characterization of detonation gun thermal spray coatings on SA213T91 in simulated boiler environment

The Ni-Cr and Stellite-21 coated SA213T91 boiler steel deposited by D-gun thermal spray process on the boiler steel were oxidized in the presence of air and Na2SO4-60% V2O5 salt mixture at 900˚C for 100 cycles. One cycle consists 1 hour heating in silicon carbide tube furnace and 20 minute cooling in ambient air. The kinetics of oxidation shows that the D-gun spray coating s technique is better than other coating techniques. The measurements of mass change kinetics corrosion by SEM/EDS, XRD and X-Ray techniques. The Oxidation and hot corrosion mechanisms were sustained by analyzing the results from various techniques. The results of the study have been discussed w.r.t. thermo gravimetric structure.

Erosion studies of cermet-coated ASTM A36 steel

PurposeThis paper aims to perform the solid particle erosion studies in simulated coal-fired boiler conditions with a view to compare the erosion behavior of two different types of detonation gun (D-Gun) sprayed cermet coating powders, that is, WC-12%Co and Cr3C2-25%NiCr on ASTM A36 steel and bare (uncoated) ASTM A36 steel.Design/methodology/approachErosion studies were performed using an air jet erosion test rig at impingement angles of 45°, 60° and 90°. During the erosion studies weight loss, erosion rates in terms of volume loss (mm3/g) and measurement of erosion profiles were determined using optical profilometer.FindingsBoth cermet coatings had successfully protected the ASTM A36 steel from erosion at impingement angles of 45°, 60° and 90°. In the case of bare ASTM A36 steel, the erosion rates were maximal at an impingement angle of 45° and minimal at an impingement angle of 90°, thus depicting the peculiar erosion behavior of ductile materials. WC-12%Co coated specimens exhibited erosion behavior that is closer to the behavior of ductile materials. Cr3C2-25%NiCr coated specimens exhibited the maximum erosion rate at an impingement angle of 90° and minimum at an impingement angle of 45°, hence depicting the typical behavior of brittle materials.Practical implicationsIt is expected that these results will contribute to the improvement of erosion resistance of induced draft fans, by the application of D-Gun sprayed WC-12%Co and Cr3C2-25%NiCr cermet coatings.Originality/valueThis paper evaluates the solid particle erosion behavior of bare and cermet-coated ASTM A36 steel which will be helpful in choosing the suitable cermet coating for induced draft fan applications.

Tribological behaviour of a self-lubricated GO/WC–12Co thermal spray coating

ABSTRACTIn this work, we report on the first thermal spray coatings to consist of graphene oxide (GO) embedded in a WC–12Co matrix. The purpose of these coatings is to release lubricant into the system when needed. These coatings were prepared using detonation gun spraying, and tribological tests of the coatings were performed. The results indicated that a coating containing embedded GO exhibited approximately half the wear rate and a 28% lower friction coefficient than a comparable coating without GO. These results were attributed to the presence of GO platelets adhering to the friction surface that formed a self-lubricating layer.

Structure and properties of detonation gun sprayed coatings from the synthesized FeAlSi/Al2O3 powder

Structure and properties of detonation gun sprayed (DS) coatings from the synthesized FeAlSi/Al2O3 powder have been investigated. The powder was manufactured through a mechanically assisted self-propagating high-temperature synthesis route. A small addition of nanosized SiO2 particles to the reaction mixture for the synthesis of FeAl-FeAl2 eutectoid refines the thickness of B2-FeAl lamellar grains in the synthesized powder. Silicon arisen from the aluminothermic reduction of SiO2 during the synthesis is preferentially located in the B2-phase. High-quality coatings with porosity less than 1 vol% and nanocomposite structure have been obtained from the synthesized powder using a computer-aided ‘Perun-S’ detonation gun complex. Phase composition of the coatings includes B2-FeAl, hercinite FeAl2O4, FeAl2, A2-Fe-based solid-solution, Al2O3, and probably complex Fe2.95Si0.05O4 oxide. It is formation of nanocomposite structure with the mean crystallite size of main components in the range of ≈9–15 nm that seems to be responsible for the lower microhardness of the coatings from the FeAlSi/Al2O3 powder than that of the basic Fe-Al eutectoid composition. As-sprayed coatings from the synthesized FeAlSi/Al2O3 powder demonstrate good room and elevated temperature erosion behavior. Oxide dominated erosion with mixed brittle-ductile wear behavior is thought to occur in the coatings at 550 °C. The proposed powder modification is found to be beneficial for the oxidation resistance of DS coatings in air at 950 °C. Promoting of alumina formation during oxidation and the corresponding decline in Fe2O3 content in the oxide scale are considered as the main reasons for the slower oxidation kinetics of the FeAlSi/Al2O3 coatings as compared with those of the basic Fe-Al eutectoid composition.

Enhancement of mechanical and wear properties of tungsten carbide coated AA 6063 alloy using detonation gun technique

ABSTRACTAluminium 6063 alloy as substrate was coated with WC-12% Co using the detonation spray gun technique. The coated specimen showed 5.6x increase in hardness over the uncoated substrate. Wear analysis was conducted on the coated specimen based on Taguchi’s L27 orthogonal by taking load (10, 20, 30 N), sliding velocity (1, 2, 3 m s−1) and sliding distance (750, 1250, 1750 m) as parameters. Wear rate was observed to increase with an increase in load and sliding velocity, whereas initial increase and a subsequent decrease in wear rate was observed with an increase in sliding distance. Analysis of variance predicted that load has a higher influence on the loss of material. Load and sliding distance interaction showed a high influence over loss of material than any other individual parameter’s influence. SEM and XRD analysis was conducted over worn surfaces to help elucidate the wear mechanism. The results from the present work may find application in piston rings and cylinder liners.

Oxidation resistance of uncoated & detonation -gun sprayed WC-12Co and Ni-20Cr coatings on T-22 boiler steel at 900°C

Oxidation is the major degradation problem in aircraft, marine, coal fired boilers, factories, and sand-bar gas turbines. It is due to the usage of variety of fuels coupled with elevated working temperatures, which dominances to the degradation in all the applications. In the present investigation oxidation behavior of uncoated and detonation Gun sprayed WC-12Co and Ni-20Cr coatings on T-22 boiler steel has been investigated at 900°C in Silicon wire tube furnace for total duration of 50 cycles under cyclic condition, each cycle consisted of keeping the samples for 60 minutes at 900°C temperature followed by 20 minutes cooling at room temperature. Oxidation kinetics of uncoated and coated sample has been established with the help of weight gain measurements. The exposed samples were characterized by scanning electron microscopy/energy dispersive spectroscopy (SEM&EDS).The Ni-20Cr coating, with morphological observations was found to be more protective than uncoated and WC-12Co coated on T-22 boiler steel.

Effect of coating thickness on microstructure and low temperature cyclic thermal fatigue behavior of thermal barrier coating (Al2O3)

Effect of coating thickness on low temperature cyclic thermal fatigue behaviour of Al2O3 thermal barrier coating (TBC) was concluded through the cyclic furnace thermal fatigue test (CFTF). Detonation gun (Thermal Spray) process was used for bond coating of NiCr and top coating of Al2O3 on Aluminium Alloy 6061 substrate. Top coating was done at two level of thickness to investigate the effect of coating thickness on low temperature cyclic thermal fatigue. The top coat of thickness 100μm-150μm was considered as thin TBC while the top coat of thickness 250μm-300μm was considered as thick TBC. The thickness of bond coat was taken as 120μm constant for both level of Al2O3 top coating. During CFTF test appearance of any crack on coated surface was adapted as main criterion of coating failure. Crack initiation was observed at edges and corner of thin thermal barrier coating after 60 number of thermal fatigue cycles while in case of thick thermal barrier coating these crack initiation was observed after 72 cycles of cyclic thermal fatigue test. During the study, it was observed that thick thermal barrier coating survived for long duration in comparison of thin TBC. Hence it can be concluded that application of thick TBC is more favourable to improve thermal durability of any component.

Corrosion performance of Cr3C2-NiCr+0.2%Zr coated super alloys under actual medical waste incinerator environment

Incineration techniques are widely used to dispose of various types of waste which lead to formation of very corrosive environment. Such corrosive environment leads to the degradation of the alloys used in these areas. To obviate this problem, zirconium modified Cr3C2-(NiCr) coating powder has been deposited on three superalloys namely Superni 718, Superni 600 and Superco 605 using Detonation gun technique. Corrosion test was conducted in actual medical waste incinerator environment. The samples were hung inside the secondary chamber operated at 1050°C for 1000h under cyclic condition. Corrosion kinetics was monitored using the weight gain measurements and thickness loss. Corrosion products were characterized using scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction technique. It was observed that coating is found to be successful in impeding the corrosion problem in superalloys.

A Comparison of Wear Due to Abrasion of WC–Ni Coatings on Aluminium Alloy Sprayed by HVOF and Detonation Gun

In this investigation, aluminum alloy is coated with WC–Ni layer deposited by detonation spraying and high velocity oxy fuel (HVOF) spraying. The important features of microstructure and hardness of the coating are characterized extensively. The wear rates of the coating due to abrasion are determined for different applied loads. The worn coatings are examined under scanning electron microscopy. A correlation is established between the wear rates of the coatings due to abrasion and hardness. The results show that abrasion action takes place by both particle rolling and particle sliding. Fracture of particles during abrasion increases wear rate. In general, the wear rate due to abrasion is higher for the coating deposited by detonation spraying than that of coating deposited by HVOF spraying.

Investigation on the Influence of Substrate Materials on the Tribological Behavior of Detonation Gun Sprayed Alumina Coating

Investigation on the Influence of Substrate Materials on the Tribological Behavior of Detonation Gun Sprayed Alumina Coating

Solid particle erosion studies of D-gun sprayed cermet coatings on ASTM A36 steel

Erosion studies were performed in simulated coal-fired boiler conditions with a view to compare the erosion behaviour of two different types of detonation gun (D-gun) sprayed cermet coating powders, i.e., WC-12%Co and Cr3C2-25%NiCr on ASTM A36 steel and bare (uncoated) ASTM A36 steel. During the erosion studies weight loss, erosion rates in terms of volume loss (mm3/g) and measurement of erosion profiles were determined utilising optical profilometer. All the two different types of D-gun sprayed cermet coatings had successfully protected the ASTM A36 steel from erosive wear at impingement angles of 45o, 60o and 90o. In the case of bare ASTM A36 steel specimens the solid particle erosion rates were maximal at an impingement angle of 45o that was reduced at an impingement angle of 60o and minimal at an impingement angle of 90o that is the typical erosive wear behaviour of ductile materials. WC-12%Co coated specimens exhibited erosive wear behaviour that is closer to the behaviour of ductile materials. Cr3C2-25%NiCr coated specimens exhibited the maximum volume erosion rate at an impingement angle of 90o which was reduced at an impact angle of 60o and minimum at an impingement angle of 45o hence depicted the typical behaviour of brittle materials.

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

PurposeHot 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/approachThe 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.FindingsDuring 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/implicationsTherefore, 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 implicationsThis research is useful for coal-fired boilers and other power plant boilers.Social implicationsThis research is useful for power generation plants.Originality/valueThere 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.

Thermo-electrical properties of the alumina coatings deposited by different thermal spraying technologies

Abstract Thermal and electrical properties of alumina (Al 2 O 3 ) coatings produced via Atmospheric Plasma Spraying (APS) and Detonation Gun Spraying (DGS) were investigated and compared in this study. A combination of Scanning Electron Microscopy (SEM), Energy Dispersive X-ray (EDX) analysis, image analysis and X-ray Diffraction analysis (XRD) were used to better understand microstructural characteristics of as-sprayed alumina coatings. Microstructure formation of coating layers and its main features such as splats, pores, and boundaries were experimentally observed for both deposited coatings. The measurement of splats average thickness indicated that splat sizes, as building blocks of coatings were approximately similar for both coatings. The XRD showed that feedstock was pure α-Al 2 O 3 , but both deposited alumina coatings contained the mixture of α-Al 2 O 3 and γ-Al 2 O 3 phases. However, the amount of α-Al 2 O 3 phase was two times higher in DGS deposited coating. The DGS deposited coatings were also had a higher hardness compared to APS deposited one. The electrical properties of alumina coatings were measured using the pseudo two-contact impedance spectroscopy method that allowed separation of the electrical resistivity of splats and their boundaries within the coating microstructure. The obtained results showed significant difference between these two features in terms of electrical resistivity, namely splats had 5 orders of magnitude smaller resistivity compared to the splat boundaries. In addition, DGS deposited coating was characterized with higher electrical resistivity of splats and splat boundaries compared with APS coating. Finally, the experimentally measured thermal conductivities of alumina coatings showed higher thermal conductivity in DGS deposited coatings compared to the APS ones. These values were validated using analytical models and Finite Element Analysis (FEA).

Evaluation of Thermal Spray Alumina Coatings on Nickel Electrode Connector for Reprocessing Applications

Electro-oxidative dissolution of the spent mixed oxide nuclear fuels with high plutonium content from prototype fast breeder reactor need to be carried out in boiling 11.5 M HNO3. Nickel electrode connectors employed in the electrolyser of the dissolver should possess good corrosion resistance as well as good electrical conductivity. Alumina coating deposited on Ni by plasma spraying was evaluated by electrochemical polarization and impedance experiments in 11.5 M HNO3 at room temperature. In order to improve corrosion resistance, alumina coating relatively denser than plasma spray coating was deposited over Ni by detonation gun (D-gun) spray coating. This alumina coating exhibited a high insulation resistance and the weight loss of alumina coated Ni disc was only 3% compared to 29% for bare Ni disc sample when exposed to the vapour of 11.5 M boiling HNO3 for 12 h. However, coating delamination observed at the alumina/bond coat interface was attributed to the penetration of HNO3 vapour through the pores in the coating. Since alumina coating deposited by D-gun technique over Ni was also found to offer only short-term protection against corrosion due to HNO3 vapour, monolithic dense alumina sleeve fabricated through powder metallurgy route was recommended instead of coating, for better corrosion protection in HNO3 vapour compared to thermal spray coating.

Hot Corrosion behaviour of Nanostructured Cermet based Coatings Deposited by Different Thermal Spray Techniques: A Review

Hot corrosion is a serious problem in power plants, boilers, gas turbine and internal combustion engines. There are several alloys and super alloys which are capable to protect the components within a certain limit. So many coatings are widely used to improve service life of components by providing better erosion-corrosion resistance to the substrate. This review is essentially based on the hot corrosion behavior of Nanostructured and conventional Cr3C2-NiCr coatings deposited by several thermal spray techniques. This review is done to summarize the various properties of Chrome carbide nickel chrome coatings deposited by different methods and the hot corrosion behavior of both Nanostructured and conventional coatings in molten salts environment.High-velocity oxy-fuel (HVOF) spraying method is effective method to deposit dense and less porous coatings but a new method has been developed known as Detonation gun (D-Gun) coating,deposited by D-gun has low porosity and high bond strength than HVOF. Plasma spray is also thermal spray technique which possess less porosity, high bond strength, good abrasive and wear resistance and high hardness value but the cost of equipment is very high which is the limitation of this method. The main aim of the review is to summarize the performance of Cr3C2-NiCr coatings in various environment and to study the effect of coating parameters such as coating thickness & porosity on the hot corrosion behavior.

Wear Between Ring and Traveler: A Pin-On-Disc Mapping of Various Detonation Gun Sprayed Coatings

A textile mill provides one of the hardest and rigorous environments to a ring and a traveler of a spinning machine. Generation of high contact pressure between the ring and the traveler during winding led to degradation of the internal surface of the ring, thus its working life. This study elucidated towards enhancing the working life of the ring as well as decreasing the time required to reinstate the rings on the spindle periodically during spinning. The objective was carried out by comparing four different detonation gun (D-Gun) thermal sprayed coatings on bearing alloy steel (E52100) ring in a laboratory test using pin-on-disc apparatus. The microstructure and mechanical properties of the WC-Co-Cr, Cr3C2NiCr, Al2O3+TiO2 (Alumina-Titania) and Stellite-6 coatings were comparatively studied with those of uncoated E52100. The coated E52100 showed significantly less wear loss as compared to bare E52100. The investigations revealed that the cumulative volume loss for detonation sprayed coatings increased with increase in load. The WC-Co-Cr coating underwent minimum wear and the WC-Co-Cr–E52100 coating-substrate combination exhibited highest abrasive wear resistance. The results obtained during pin-on-disc laboratory test may be used for comparison of wear resistance of different coatings deposited on E52100 alloy steel rings in the textile mill.

Study of High-Temperature Corrosion Behavior of D-Gun Spray Coatings on ASTM-SA213, T-11 Steel in Molten Salt Environment

Alloys and metals get corroded when exposed to high temperature in air or in actual boiler environment in thermal plants. In the present study, a Ni-20Cr coating was deposited by detonation gun process on ASTM–AS-213, T-11 boiler steel. Cyclic corrosion studies were carried out in molten salt environment at 900°C for 50 cycles. Each cycle consist of 1 hour heating in Silicon carbide tube furnace followed by 20 minutes cooling in air. The kinetics of weight gain or loss was measured after each cycle and visually examined, the surface studies of the exposed samples were characterized by SEM/EDS and XRD analysis. The results obtained showed the better performance of Ni-20Cr coated T-11 boiler steels than the uncoated T-11 boiler steel.© 2014 The Authors. Elsevier Ltd. All rights reserved.Selection and peer-review under responsibility of the conference committee members of the 4th International conference on Materials Processing and Characterization.

Surface Engineering Analysis of D-Gun Sprayed Cermet Coating in Aggressive Environment

Material degradation due to hot corrosion is a common problem in many engineering system, including coal fired turbines, valves and boiler tubes leading to huge economy losses. Detonation Gun process is a novel coating deposition process among the other thermal spray processes due to its very low porosity, strong adhesion to substrates, high cohesive strength and high hardness. In the present investigation, D-Gun process has been used to deposit Cr3C2–25NiCr coating on 23/8N Nitronic steel. The oxidation behavior of D-Gun sprayed Cr3C2–25NiCr coatings subjected to high temperature (700°C) in actual coal fired boiler for 1000 hours has been carried out in the present work. X-ray diffraction, Field emission–scanning electron microscope technique was used to analyze the scales formed on the surface of the oxidized samples. High volume fraction of carbides contributed for the higher microhardness of the coating (970HV). No microspalling of the scales were showed by the coated specimen. The scale remained intact and adherent to the substrate. The development of protective oxide scale of chromium, nickel and spinel of nickel and chromium have contributed the better oxidation resistance for coated specimen. The Cr3C2-25 NiCr coating imparted better hot corrosion resistance than the uncoated one in the given environment.

A study of thermal spray coated surface with nano composite powder of CNT+WC14C0

Coatings obtained from thermal spray process are being developed for wide varieties of applications in aerospace and automotive industries. To enhance the wear resistance in the YAWING in wind mills, a new study is required to find out and analyze the surface properties of the surface of Yawing. In this study to enhance the surface properties, a new nano composite powder has been developed and coated on SS304. To synthesis of CNT+WC14Co, initially a binder material of 0.5% Poly Vinyl alcohol solution was prepared and made use as a binder between CNT and WC14Co particles. The synthesized nano composite powder is coated over SS304 samples as per Taguchi design of experiments by Detonation gun coating technique. The coated samples are undergone the tests of micro hardness and Surface roughness. It was found that a significant improvement in micro hardness and there is no significant improvement in surface finish. The best combination of input parameters is obtained through Taguchi method and untried combination's results also have been predicted through Taguchi method. Response surface methodology (RSM) is used to develop a mathematical model.

Fabrication, tribological and corrosion behaviors of detonation gun sprayed Fe-based metallic glass coating

A metallic glass coating with the composition of Fe51.33Cr14.9Mo25.67Y3.4C3.44B1.26 (mole fraction, %) on the Q235 stainless steel was developed by the detonation gun (D-gun) spraying process. The microstructure and the phase aggregate were analyzed by scanning electron microscopy and X-ray diffractometry, respectively. Microhardness, wear resistance and corrosion behavior were assessed using a Vickers microhardness tester, a ball-on-disk wear testing machine and the electrochemical measurement method, respectively. Microstructural studies show that the coatings possess a densely layered structure with the porosity less than 2.1%. The tribological behavior of the coatings examined under dry conditions shows that their relative wear resistance is five times higher than that of the substrate material. Both adhesive wear and abrasive wear contribute to the friction, but the former is the dominant wear mechanism of the metallic glass coatings. The coatings exhibit low passive current density and extremely wide passive region in 3.5% NaCl solution, thus indicating excellent corrosion resistance.