Detonation Gun Research Articles

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.

High Temperature Corrosion Resistant and Anti-slagging Coatings for Boilers: A Review

AbstractHigh temperature corrosion and slag deposition significantly reduce the thermal efficiency and lifespan of biomass-fired boilers. Surface modification with protective coatings can enhance boiler performance and prevent commercial losses due to maintenance and damage. This review focuses on the development of corrosion-resistant coatings (CRCs) and anti-slagging coatings (ASCs) over the past decade. CRCs are explored through thermal spray processes that include arc spray, atmospheric plasma spray (APS), high-velocity oxygen fuel (HVOF), detonation gun (D-gun™), and cold spray. Studies on alloys, ceramics, and ceramic–metal composites are summarised, highlighting the high temperature corrosion prevention mechanisms and discussing new coating materials. ASCs are reviewed in the context of advancements via thermal spray and slurry spray methods. The mechanisms for slag reduction, testing methods to evaluate ASC effectiveness, and the necessary architecture for preventing slag deposition are examined. A lab-based rig simulating fly ash deposition onto water-cooled coating coupons for anti-slagging investigations is also presented. Further research is needed to develop and evaluate materials for ASCs effectively. Graphical Abstract

Gasification of Liquid Hydrocarbon Waste by the Ultra-Superheated Mixture of Steam and Carbon Dioxide: A Thermodynamic Study

The thermodynamic modeling of waste oil (WO) gasification by a high-temperature gasification agent (GA) composed of an ultra-superheated H2O/CO2 mixture is carried out. The GA is assumed to be obtained by the gaseous detonation of fuel–oxidizer–diluent mixture in a pulsed detonation gun (PDG). N-hexadecane is used as a WO surrogate. Methane or the produced syngas (generally a mixture of H2, CO, CH4, CO2, etc.) is used as fuel for the PDG. Oxygen, air, or oxygen-enriched air are used as oxidizers for the PDG. Low-temperature steam is used as a diluent gas. The gasification process is assumed to proceed in a flow-through gasifier at atmospheric pressure. It is shown that the use of the detonation products of the stoichiometric methane–oxygen and methane–air mixtures theoretically leads to the complete conversion of WO into a syngas consisting exclusively of H2 and CO, or into energy gas with high contents of CH4 and C2-C3 hydrocarbons and an LHV of 36.7 (fuel–oxygen mixture) and 13.6 MJ/kg (fuel–air mixture). The use of the detonation products of the stoichiometric mixture of the produced syngas with oxygen or with oxygen-enriched air also allows theoretically achieving the complete conversion of WO into syngas consisting exclusively of H2 and CO. About 33% of the produced syngas mixed with oxygen can be theoretically used for PDG self-feeding, thus making the gasification technology very attractive and cost-effective. To self-feed the PDG with the mixture of the produced syngas with air, it is necessary to increase the backpressure in the gasifier and/or enrich the air with oxygen. The addition of low-temperature steam to the fuel–oxygen mixture in the PDG allows controlling the H2/CO ratio in the produced syngas from 1.3 to 3.4.

Corrosion tests on austenitic samples with alumina and alumina-forming coatings in oxygen-containing stagnant Pb and turbulently flowing PbBi

Two differently produced alumina coatings (by pulsed laser deposition (PLD) and detonation gun (DG)) and one alumina-forming coating realised by pack cementation are proposed as a protection barrier against corrosion of austenitic steels in Pb and PbBi. Samples were tested in oxygen-controlled stagnant Pb (10−7 wt.%) at 480 °C and 550 °C for up to 10,000 h and in turbulently flowing (up to 1.6 m/s) PbBi eutectic at 490 °C with 10−9–10−8 wt.% oxygen for about 500 h. All exposed coatings showed a good behaviour in flowing PbBi and in stagnant Pb at around 480 °C independent of the oxygen content. At 550 °C, the PLD coating failed most probably due to incomplete coating of the sample, while the DG sample protected the base material.

Thermo-Mechano-Chemical Processing of Printed Circuit Boards for Organic Fraction Removal

Printed circuit boards (PCBs) are the main components of e-waste. In order to reduce the negative impact of waste PCBs on human health and the environment, they must be properly disposed of. A new method is demonstrated for recycling waste PCBs. It is referred to as the high-temperature thermo-mechano-chemical gasification (TMCG) of PCBs by the detonation-born gasification agent (GA), which is a blend of H2O and CO2 heated to a temperature above 2000 °C. The GA is produced in a pulsed detonation gun (PDG) operating on a near-stoichiometric methane–oxygen mixture. The PDG operates in a pulsed mode producing pulsed supersonic jets of GA and pulsed shock waves possessing a huge destructive power. When the PDG is attached to a compact flow reactor filled with waste PCBs, the PCBs are subject to the intense thermo-mechano-chemical action of both strong shock waves and high-temperature supersonic jets of GA in powerful vortical structures established in the flow reactor. The shock waves grind waste PCBs into fine particles, which undergo repeated involvement and gasification in the high-temperature vortical structures of the GA. Demonstration experiments show full (above 98%) gasification of the 1 kg batch of organic matter in a setup operation time of less than 350 s. The gaseous products of PCB gasification are mainly composed of CO2, CO, H2, N2, and CH4, with the share of flammable gas components reaching about 45 vol%. The solid residues appear in the form of fine powder with visible metal inclusions of different sizes. All particles in the powder freed from the visible metal inclusions possess a size less than 300–400 μm, including a large fraction of sizes less than 100 μm. The powder contains Sn, Pb, Cu, Ni, Fe, In, Cd, Zn, Ca, Si, Al, Ti, Ni, and Cl. Among these substances, Sn (10–20 wt%), Pb (5–10 wt%), and Cu (up to 1.5 wt%) are detected in the maximum amounts. In the powder submitted for analysis, precious elements Ag, Au, and Pt are not detected. Some solid mass (about 20 wt% of the processed PCBs) is removed from the flow reactor with the escaping gas and is partly (about 10 wt%) trapped by the cyclones in the exhaust cleaning system. Metal inclusions of all visible sizes accumulate only in the flow reactor and are not detected in powder samples extracted from the cyclones. The gasification degree of the solid residues extracted from the cyclones ranges from 76 to 91 wt%, i.e., they are gasified only partly. This problem will be eliminated in future work.

Effect of detonation spray regimes on photocatalytic activity of Ti-TiO2 coatings

The influence of the regimes of detonation spraying the Ti-TiO2 based coatings on its photocatalytic properties is studied. The spray distance and the speed of passage of the detonation gun are varied when the coatings are applied. The microstructure and phase composition are studied. It is found that proportion of rutile prevails over the other phases in all samples obtained under all spray regimes used. The kinetics of photocatalytic reaction basing on Langmuir-Hinshelwood model of heterogeneous photocatalysis is analyzed. The photocatalytic activity and the rate constant of photocatalytic reaction of the coatings decrease with an increase in the spray distance. New equation describing the dependence observed is proposed. The decrease in the rate constant occurs according to a power law. The photocatalytic activity and the rate constant of the photocatalytic reaction of coatings increase with an increase in the rutile percentage. New equation describing such dependence is proposed. The increase occurs according to an exponential law. The photocatalytic rate constant depends on the speed of passage accordingly with a parabolic law.

Effect of HT Cycling in Air on Microstructure of Detonation Gun Sprayed YSZ/NiCr Coating

Effect of HT Cycling in Air on Microstructure of Detonation Gun Sprayed YSZ/NiCr Coating

Comparative studies on oxidation behaviour of cobalt-based D-gun coatings on boiler steel

The protection system against material degradation at elevated temperatures is gaining technological importance. Three cobalt-based coatings were developed on SAE213-T91 boiler steel using the detonation gun method. The oxidation performance of all the specimens was examined for 50 cycles of 1 h heating at 900 °C in a thermal cyclic furnace and 20 min cooling at 25 °C outside the furnace. All the oxidised samples were investigated through SEM/X-ray mapping and an X-ray diffraction analyser. All the specimens obeyed the parabolic rate law of oxidation approximately. The oxidation resistance of Stellite 6 coating was found to be superior among all coated and uncoated specimens due to the growth of protective oxide Cr2O3 and CoCr2O4 spinel in it. The development of Ni, Cr and Co oxides in Stellite 21 coating resulted into its slow oxidation rate, whereas the growth of the non-protective WO3 and CoWO4 phases in WC-Co coating caused its rapid oxidation.

Microstructural and Tribological Characteristics of Composites Obtained by Detonation Spraying of Iron-Based Alloy-Carbide Powder Mixtures.

iron-based coatings have exhibited good mechanical properties, such as high hardness and good wear resistance, which are desirable properties in applications such as automobile brake rotors. iron-based coatings are also good replacements for Co- and Ni-based coatings, which are costly and could have health and environmental concerns due to their toxicity. In this research, three different iron-based coatings were deposited using the Detonation Gun Spraying (DGS) technology onto aluminum substrates, including the steel powders alone (unreinforced), and steel powders mixed with Fe3C and SiC particles, respectively. The microstructural characteristics of these coatings and mechanical properties, such as hardness and wear resistance, were examined. The morphology and structure of the feedstock powders were affected by the exposure to high temperature during the spraying process and rapid solidification of steel powders that resulted in the formation of an amorphous structure. While it was expected that steel particles reinforced with hard ceramic particles would result in increased hardness, instead, the unreinforced steel coating had the highest hardness, possibly due to a higher degree of amorphization in the coating than the other two. The microstructural observation confirmed the formation of dense coatings with good adhesion between layers. All samples were subjected to ball-on-disk wear tests at room temperature (23 °C) and at 200 °C. Similar wear resistances of the three samples were obtained at room temperature. At 200 °C, however, both ceramic reinforced composite samples exhibited higher wear rates in line with the reduction in their hardness values. This work explains, from the microstructural point of view, why adding hard particles to steel powers may not always lead to coatings with higher hardness and better wear resistance.

Sai Coating: Detonation Spray Gun

Sai Coating, a small entrepreneurial firm, was one of the three firms that had received the license from ARCI for marketing the Detonation Spray Coating (DSC). Sai Coating made and sold the detonation gun (D-Gun) to three sectors, namely: Wire Drawing, Textiles and Aero components. The coating enhanced the life of the coated wire or surface and its functionality in some ways. The firm had a turnover of INR 4,500,000 and was looking to generate scale and maximize its revenues. The case revolves around the pricing strategy to be adopted by Sai coating to extract value from different set of customers. What should be the price levels given the nature of the product?

Fabrication of Large Alumina Grit-Based Monolayer Grinding Wheel through Electroplating Followed by Detonation Gun Spray Technique for Increased Material Removal

Fabrication of Large Alumina Grit-Based Monolayer Grinding Wheel through Electroplating Followed by Detonation Gun Spray Technique for Increased Material Removal

Effect of coating degradation on the hot corrosion behavior of yttria-stabilized zirconia (YSZ) and blast furnace slag (BFS) coatings

In order to provide thermal insulation thermal barrier coatings (TBCs) used in gas turbine engine components under conditions of impure fuels and high turbine inlet temperatures are expected to have hot corrosion resistance. Techniques and material combinations used in the production of TBCs are primarily effective in the progression of failure mechanisms as a result of hot corrosion. In this study, the hot corrosion damage mechanism, which is caused by the impurities of the fuels used in the industry and causes great damage to the TBC systems, was simulated and evaluated in the laboratory environment. For the creation of TBC systems, CoNiCrAlY metallic bond coating powders were deposited on Ni-based super alloy substrates by the detonation gun (D-gun) process. Commercial yttria-stabilized zirconia (YSZ) and blast furnace slag (BFS) powders were deposited on the bond coating by Atmospheric plasma spraying (APS) technique. Hot corrosion testing of TBCs was performed at 800 °C for 8, 24, 50, and 75 h in an environmental condition consisting of a 45 wt% Na2SO4 and 55 wt% V2O5 corrosive salt mixture. Blast furnace slag, which is completely cost-free and a waste product, provided excellent protection against hot corrosion damage without deteriorating its stability at high temperatures. In this way, it is open to be evaluated as a new type of coating material alternative to the traditional top coating material YSZ, which has a very high production and cost, and to be used in different areas.

Structural characteristics, oxidation performance and failure mechanism of thermal barrier coatings fabricated by atmospheric plasma spraying and detonation gun spraying

In recent years, thermal barrier coatings (TBCs) are widely applied to the surface of gas-turbine engines to prolong the service life of high temperature components. The increase in raw material requirements and costs has led to the search for an alternative, cheaper ceramic based material to yttria stabilized zirconia (YSZ), which is the traditional TBC top coating material. In this study, CoNiCrAlY metallic bond coating powders were deposited on Ni-based superalloy substrates by the detonation gun (D-gun) process. Commercial YSZ and blast furnace slag (industrial waste) powders were deposited on the bond coating by atmospheric plasma spraying (APS) technique. TBCs were subjected to isothermal oxidation tests for 8, 24, 50, and 75 h at 800 °C. The microstructural properties of the TBCs were evaluated comparatively using advanced characterization techniques before and after oxidation tests. It has been observed that the coatings produced using BFS material have a potential to be used in different types of industries as a low-cost and environmental solution against high temperature oxidation conditions.

High temperature tribological properties of the D-gun WC-12Co coating in fluoride molten salt

Development of anti-corrosion and wear-resistant materials in FLiNaK molten salt is vital to the service safety and reliability of the various mechanical systems for the molten salt reactor. In this work, a WC-12Co coating was fabricated by detonation gun spraying technique. Its microstructure, mechanical properties and tribological behaviors in FLiNaK molten salt were studied. A ball-on-disk rotary configuration was selected for the tribological test, in which the WC-12Co coating disks slid against Al2O3, SiC, Si3N4 and steel counterface materials in FLiNaK molten salt and low-oxygen environment at 600 °C. The results showed that the WC-12Co coating displays a low porosity of 0.71%, a bonding strength of above 44 MPa and good anti-corrosion in molten salt. FLiNaK molten salt provides the good lubricity and inhibits the oxidation wear of the WC-12Co coating, contributing to the low friction coefficient of 0.097–0.17 and wear rate of (4.95–8.40) × 10−7 mm3N−1m−1.

Tribological properties of NiCrAlYTa-Ag self-lubricating coatings at wide temperature range by detonation spraying

High-temperature self-lubricating materials are an appropriate choice to solve the problem of friction and wear for elevated temperature mechanical systems. In this study, NiCrAlYTa-Ag self-lubricating coatings used in a wide temperature range were prepared by the detonation gun spraying method. According to the findings, NiCrAlYTa-Ag coatings are composed of γ/γ', β-NiAl and Ag phases. The hardness and bonding strength of the coating decrease with the addition of Ag, and the coating with 20 % Ag has a high bonding strength of 43 MPa and a hardness of 303 Hv. The coating exhibited a friction coefficient of 0.35–0.47 and a wear rate of 4 × 10−5–6 × 10−5 mm3/N m From room temperature to 900 °C. At low temperatures, lubrication behavior was mainly attributed to the formation of Ag films. Excitingly, the AgTaO3 with good lubrication performance was created at high temperatures by a tribo-chemical reaction, which plays a synergistic lubrication role with Ta2O5, NiO, and Cr2O3.

Gasification of Waste Machine Oil by the Ultra-Superheated Mixture of Steam and Carbon Dioxide

Reported in the article is further progress in the development of the novel pulsed detonation gun (PDG) technology for the conversion of organic wastes into syngas in a two-component gasifying agent (GA) containing ultra-superheated steam and carbon dioxide obtained by pulsed detonations of a natural gas–oxygen mixture at a frequency of 1 Hz. Experimental studies were carried out on a waste converter with a 40 dm3 flow reactor and two PDGs with a total volume of 2.4 or 3.2 dm3, which is approximately a factor of 6 and 4.5 less than in previous studies, respectively. The objective of the research was to find the design and operation parameters of the waste converter that provide a minimum amount of CO2 in the gasification products. Waste machine oil was used as a feedstock. It is shown that, compared with the earlier experiments with a higher average temperature of the reactor wall and with a PDG of a much larger volume, the contents of H2, CO, CH4, and CO2 in the syngas remained virtually unchanged, whereas the efficiency of the gasification process increased significantly: the use of 1 g of natural gas made it possible to gasify up to 4 g of the feedstock. It is also shown that the determining role in the gasification process of liquid feedstock is played by the feedstock residence time in the PDG rather than in the reactor. The minimum ratio between the flow rates of the GA and liquid feedstock, the minimum ratio between the flow rates of combustible gas and liquid feedstock, as well as the actual GA consumption in the gasification process are determined experimentally.

Thermal Spray Coating Technology – A Review

Thermal spray coating involves heating of coating materials (ceramic, carbide, and metal alloys) to a semi-molten or molten state and propels to substrate. The flame temperature is in the range of 3,000 to 16,000OC but the surface temperature of the substrate rarely exceeds 500 OC depending on the thermal spray processes being used. The coating materials are feed into the spray gun in the form of powders, rods or wires. Thermal spray coating is use for the following purposes; (i) increase corrosion and wear resistance, (ii) protection against electromagnetic, or electrostatic, (iii) protection against radio frequency interference, (iv) metal buildup and, (iv) cosmetic. Thermal spray coating can be categorized into five most common processes; (i) Flame arc spraying, (ii) Electric Arc spraying, (iii) Plasma arc spraying, (iv) High-velocity Oxy/Fuel (HVOF) and (v) Detonation Gun. In this paper, thermal spraying processes will be explained, along with the advantages and disadvantages of one another.

Comparative Evaluation of Oxidation Resistance of Detonation Gun-Sprayed Al2O3–40%TiO2 Coating on Nickel-Based Superalloys at 800 °C and 900 °C

High-temperature oxidation is the major degradation mechanism of boiler and gas turbine components. Superalloys are used in these applications because of their superior mechanical properties and creep resistance, but they lack resistance to oxidation under aggressive environment. In the present investigation, Al2O3–40%TiO2 coating was deposited on Superni718 and Superni600 superalloys by a detonation gun spray process. The as-sprayed coating was characterized by SEM analysis. The high-temperature oxidation behavior of Superni718 and Superni600 and Al2O3–40%TiO2 coating on these superalloys was evaluated in air under cyclic conditions at 800 °C and 900 °C for a total duration of 50 cycles. Each cycle consisted of keeping the samples for one hour at the elevated temperature followed by 20 min cooling in ambient air. Oxidation kinetics were studied using a thermo-gravimetric technique and found to follow the parabolic rate law. The coating was successfully formulated using a detonation gun spray process. The coating was found to be adherent to the substrate superalloys. It was found that among the two alloys, uncoated and coated Superni600 superalloys have much better oxidation resistance as compared to uncoated Superni718 superalloy.

High temperature tribological properties of D-gun Al2O3 coatings in fluoride molten salts

Anti-corrosion and wear-resistance coating is important to the reliability of the mechanical systems served in molten salt media. In this work, the Al2O3 coating was prepared on the stainless steel surface by a detonation gun (D-gun) spraying technique and its high temperature tribological properties in FLiNaK molten salt were studied systematically by sliding it against SiC, Al2O3 and steel materials. The results indicated that the Al2O3 coating has a high bonding strength of above 50 MPa with a porosity of 0.8 %. The tribological properties of the Al2O3 coating is significantly influenced by the counterface materials. The friction coefficients are between 0.14 and 0.45, and the wear rate increases from 2.2 × 10−5 mm3/N·m to 19.1 × 10−5 mm3/N·m by sliding it against SiC, Al2O3 and steel materials. The worn surface morphologies and compositions were specifically studied and correlated to these distinct behaviors.

Formation of Composite Coatings during Detonation Spraying of Cr3C2

In the current practice of applying carbide-based coatings by thermal spraying, the starting material usually contains a metal binder. However, it is important to study the possibility of spraying binder-free carbides, since the metal components usually reduce the operating temperature and corrosion resistance of cermet coatings. In this work, a powder of chromium carbide, Cr3C2, was sprayed using a CCDS2000 detonation gun. Acetylene–oxygen mixtures C2H2 + kO2 with k varying from 0.8 to 3.0 were used as an energetic material. Due to chemical reactions between Cr3C2 and the detonation products, the coatings were of composite nature (multi-phase materials) with a composition depending on k. At k values in the range from 0.8 to 1.1, along with Cr3C2, the coatings contained chromium carbonitride Cr3N0.4C1.6. In the k range from 1.3 to 2.0, Cr7C3 and Cr were the main components of the coatings. As k was increased to 3.0, along with Cr7C3 and Cr, the CrO and Cr2O3 oxides formed in the coatings. The mechanical properties and wear resistance of the coatings were found to depend on their phase compositions. Coatings produced by detonation spraying of Cr3C2 powder may be useful for increasing the corrosion resistance of machine parts to mineral acids and high-temperature oxidation resistance.