Detonation Spraying Research Articles

Detonation Spraying of Ni-Based Composite Coatings Reinforced by High-Entropy Intermetallic Particles

Ni-based composite coatings reinforced by high-entropy intermetallic compounds (HEICs) were prepared by detonation spraying (DS) on low alloy steel substrates. To this end, first (Ti-Nb)(V-Cr-Ni-Fe) and Al3(TiZrNbCrHfTa) HEIC powders were fabricated by arc melting followed by ball milling. The as-milled HEIC powders were then employed as reinforcement particles to prepare Ni-7wt.% HEIC composite coatings. The average particle size of the (Ti-Nb)(V-Cr-Ni-Fe) and Al3(TiZrNbCrHfTa) HEIC powders were 18 and 35 µm, respectively, while the average particle size of the Ni powder was 56 µm. (Ti-Nb)(V-Cr-Ni-Fe) exhibited a single hexagonal C14 Laves phase in spite of Ti and Nb segregations. The XRD pattern of Al3(TiZrNbCrHfTa) indicated the presence of a tetragonal D022-type structure along with some minor CrTi and Cr5Al8 phases. The sprayed Ni-7wt.% FeNiCrV-TiNb and Ni-7wt.% Al3(TiZrNbCrHfTa) composite coatings retained crystal structures of the powder mixtures, suggesting proper thermal stability for both powders. The coatings exhibited a dense microstructure consisting of a lamellar microstructure with low porosity and sound bonding with the substrate. The microhardness of Ni-7wt.% FeNiCrV-TiNb (450 HV) was higher than that of Al3(TiZrNbCrHfTa) (338 HV), and it exhibited lower fluctuation than that of Ni-7wt.% Al3(TiZrNbCrHfTa). DS is an effective method to fabricate metal matrix composites reinforced by HEICs with a low level of porosity.

Structure and photocatalytic properties of the composite coating fabricated by detonation sprayed Ti powders

In the present study, composite coatings based on titanium oxides were successfully prepared using detonation spray coating process on two types of substrates: hot-rolled carbon steel and fine-grained hyperpressed concrete. The microstructure, phase composition and photocatalytic activity of these coatings were investigated. The structure of the coatings presents many lamellae piled up one upon another, and is composed of rutile, anatase, titanium oxide, and titanium. Coatings were studied for the photocatalytic degradation of organic pollutants such as methylene blue (MB) and rhodamine B (RhB) under UV light. The photocatalytic activity of the composite coatings based on titanium oxides also was evaluated by changing the contact angle. The results showed that composite coatings based on titanium oxides have a high photocatalytic activity on surfaces of the hot-rolled carbon steel and fine-grained hyperpressed concrete. Taking into account the results presented in this work, it is expected that the produced coatings can later be used as effective photocatalysts and can become the basis for detonation deposition of protective self-cleaning composite coatings based on TiO2.

High-entropy alloy coating deposition by detonation spraying combined with heat treatment

High-entropy alloy coating deposition by detonation spraying combined with heat treatment

INVESTIGATION OF TRIBOLOGICAL PROPERTIES OF DETONATION COATINGS BASED ON ALUMINUM OXIDE AND TUNGSTEN CARBIDE

Detonation spraying is one of the most promising variants of thermal spraying for the deposition of wear-resistant coatings. This study aims to investigate the tribological properties of coatings deposited by the detonation method using WC-12%Co and Al2O3 as examples. These are two common coating materials widely used in wear resistant applications. A computerized detonation spraying system CCDS2000 (Computer-Controlled Detonation Spraying) was used for coating deposition. The roughness parameter of the WC-Co coating has a value of Ra = 3.95 μm and that of the Al2O3 coating has a value of Ra = 2.53 μm. To investigate the detonation coatings, the coating materials were characterized and microhardness measurements were carried out. Microhardness for stainless steel 12Х18Н10Т (AISI 321, 321H) – 392.32 Hv; for WC-12Co coating – 1332.3 Hv and Al2O3 – 805.50 Hv. By results of researches the greatest resistance to all kinds of wear has coatings WC-12%Co. Al2O3 coatings can also be recommended for operation under sliding wear conditions.

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?

Tribological Properties of a Coating with Added Boron Carbide Applied by Detonation Spraying

Tribological Properties of a Coating with Added Boron Carbide Applied by Detonation Spraying

Detonation Spraying of a Cermet Coating to Improve the Surface Properties of Tool Steel Parts Produced by the Selective Laser Melting Process

Detonation Spraying of a Cermet Coating to Improve the Surface Properties of Tool Steel Parts Produced by the Selective Laser Melting Process

Fabrication of High-Entropy Alloys Using a Combination of Detonation Spraying and Spark Plasma Sintering: A Case Study Using the Al-Fe-Co-Ni-Cu System

The use of pre-alloyed powders as high-entropy alloy (HEA) coating precursors ensures a predetermined (unaltered) elemental composition of the coating with regard to the feedstock powder. At the same time, it is interesting to tackle a more challenging task: to form alloy coatings from powder blends (not previously alloyed). The powder-blend-based route of coating formation eliminates the need to use atomization or ball milling equipment for powder preparation and allows for the introduction of additives into the material in a flexible manner. In this work, for the first time, a HEA was obtained using detonation spraying (DS) followed by spark plasma sintering (SPS). A powder mixture with a nominal composition of 10Al-22.5Fe-22.5Co-22.5Ni-22.5Cu (at.%) was detonation-sprayed to form a multicomponent metallic coating on a steel substrate. The elemental composition of the deposited layer was (9 ± 1)Al-(10 ± 1)Fe-(20 ± 1)Co-(34 ± 1)Ni-(27 ± 1)Cu (at.%), which is different from that of the feedstock powder because of the differences in the deposition efficiencies of the metals during DS. Despite the compositional deviations, the deposited layer was still suitable as a precursor for a HEA with a configurational entropy of ~1.5R, where R is the universal gas constant. The subsequent SPS treatment of the substrate/coating assembly was carried out at 800–1000 °C at a uniaxial pressure of 40 MPa. The SPS treatment of the deposited layer at 1000 °C for 20 min was sufficient to produce an alloy with a single-phase face-centered cubic structure and a porosity of <1%. Interestingly, the hardness values of the as-sprayed and SPS-treated coatings were close to each other (~320 HV0.3). The hardness of the coatings measured in two perpendicular directions did not differ significantly. The features of the DS–SPS route of the formation of HEA coatings and its potential applications are discussed.

Tailoring microstructural features of Cr3C2-25NiCr coatings through diverse spray variants and understanding the high-temperature erosion behavior

Thermal sprayed Cr3C2-NiCr coatings are widely used to protect industrial components from ambient or elevated erosive degradation. Various thermal spraying techniques such as plasma spray, detonation spray (DS), high velocity oxy-fuel (HVOF) and high velocity air-fuel spray (HVAF) are widely used to deposit Cr3C2-NiCr coatings. The choice of thermal spraying technique governs the inflight particle velocity and temperature, resulting in unique coating microstructural features, characteristics and erosion performance. In this study, Cr3C2-NiCr coatings are deposited through HVAF, DS and axial plasma spray. A comprehensive comparative analysis was performed to understand the process-structure-property relationship of Cr3C2-NiCr coatings, which correlated with the room and high temperature erosion performance. HVAF spray deposited Cr3C2-NiCr coatings with preferred microstructural features and properties, ensuring superior (high/room temperature) erosive resistance. Cr3C2-NiCr coatings deposited via DS spray performed second best, while plasma sprayed exhibited defective microstructure with inferior mechanical properties, resulting in substandard erosion performance.

Development of Alumina-Titania Composite Layers on Stainless Steel through the Detonation Spray Method and Investigation of Salt Spray Corrosion Behavior along with Surface Examination

Almost every metal and alloy corrodes when used in high-temperature applications. To combat this problem, ceramic coatings on the metals can be deposited for better thermal and corrosion behavior. The present study applies an alumina-titania (Al2O3-TiO2) ceramic coating to the stainless steel (SS) surface using a detonation spray process. The surface of the coated SS is probed by optical microscopy (OM), scanning electron microscopy (SEM), and X-ray diffraction (XRD). The clear differences between coated and uncoated SS have been observed based on the SEM images. The XRD pattern indicates that the Al2O3-TiO2 coating on SS has been successfully deposited. The hardness of coated and uncoated SS surfaces is determined by using the Micro Vickers hardness tester, which claims that the hardness of the SS surface has decreased after coating. Salt spray tests were used to examine the corrosion behavior of coated and uncoated SS after 12 and 24 hours. After 12 hours, no corrosion was observed on the SS. After 24 hours, however, significant corrosion of uncoated SS is observed, and the coated SS shows negligible corrosion. Based on the study, it is claimed that an Al2O3-TiO2 coating on SS has improved its corrosion behavior significantly.

Microstructure and mechanical properties of HA/Ti composite coatings applied by detonation spraying

This work presents the results of experimental studies of the structure and mechano-tribological properties of composite coatings based on hydroxyapatite (HA) and titanium in different ratios (wt. %): 30HA-70Ti, 50HA-50Ti, 70HA-30Ti. Composite coatings with a thickness of 40-50 μm were applied to a substrate made of Grade 2 titanium by detonation spraying. Microstructures and phase compositions of as-sprayed coatings were analyzed by scanning electron microscopy and X-ray diffraction. The deposition mechanism of HA-Ti composite coatings was also examined. The results of the study showed that during detonation powder spraying from a mixture of HA-Ti, porous coatings are formed, consisting of the phases of hydroxyapatite Ca10(PO4)6(OH)2, tricalcium phosphate, titanium, and titanium oxide. It was found that with a decrease in the content of hydroxyapatite in the composite, there is a decrease in the relative content of B-type carbonate ions in the structure, as well as a decrease in the content of the mineral phase as a whole. Composite coating 30HA-70Ti wt. % is the closest in structure to stoichiometric crystalline HA (Ca/P = 1.67). At ratios of coatings 50HA-50Ti wt. %, an increase by 1.5-2 times in wear resistance is observed.

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.

Wear resistance of Fe66Cr10Nb5B19 detonation coatings under dry linearly reciprocating conditions and nanoscratch test

The Fe66Cr10Nb5B19 alloy coatings with high hardness (≈850 HV300), low porosity (less 3 %), low content of crystalline phase (less 2.5 wt.%), elevated nanohardness (average value 13.7 GPa), and high wear resistance were obtained in a wide range of detonation spraying modes. The results of dry linearly reciprocating sliding wear tests of coatings carried out according to ASTM G 133-05 are presented. The wear resistance of coatings obtained at an explosive charge of 50 – 70 % is significantly higher than that of stainless steel. The similar values of volume scratches of Fe66Cr10Nb5B19 coatings obtained at an explosive charge of 40 – 70 % are attributed to the similar values of porosity and the content of the crystalline phase. Scratch and spalling are the main mechanisms of coatings destruction during scratching with a diamond tip.

Manufacturing and the process-structure-property correlation of detonation sprayed iron coatings under an unconventional coating deposition mechanism

The detonation spraying was used to manufacture pure iron coatings under a coating deposition mechanism between that of general thermal spray and cold spray. The feedstock powders were heated to the temperatures below melting point and accelerated to the velocities comparable to that of in cold spraying. The results showed the iron coatings had very dense structure, good adhesion quality on the steel substrates, the same phase with the feedstock powders and very low oxygen and carbon-based impurities contents. The EBSD images, specific heat, thermal conductivity, micro-hardness and elastic modulus of the coatings have been detected to understand the structure and properties of the coatings. Explicit dynamic simulations with finite element method have been carried out for the studies on the coating deposition process and mechanism. Based on the above experiment and simulation results, a comprehensive emphasis on this unconventional coating deposition mechanism and the process-structure-property correlation of the iron coatings have been put forward.

Atmospheric plasma sprayed W coating/Detonation sprayed W-steel composite coating/steel substrate-based coating system for the tokamak first wall

To study the manufacturing method of the tungsten armored first wall of tokamak devices, the W-316 L steel (W-SS) composite coatings were fabricated on 316 L steel substrates by detonation spraying (DS) as the interlayer of pure tungsten coatings manufactured by atmospheric plasma spraying (APS). The main characteristics and performance under transient heat shocks of the APS W/DS W-SS /substrate-based three-layer coating system were studied and compared with the APS W/substrate-based coating system. The results showed the porosity of the DS W-SS was about 1.9% with most of the pores smaller than 70 nm. In contrast, the porosity of the APS W reached about 8.6% and most of the pores were up to hundreds of nanometers. The bonding strength tests proved that both the adhesions of APS W to DS W-SS and DS W-SS to the substrate were much higher (almost 1.5 times) than the adhesion of APS W to the substrates. The three-layer specimens performed much better than the APS W/substrate specimens during the transient heat shock tests as expected. Besides, a special microstructure variation occurred on the three-layer specimens before its damage under the tests which was considered helpful to prolong its life-span under high heat flux. In a conclusion, the DS W-SS interlayer improved the service performance of the APS W/substrate-based coating significantly and demonstrates its potential for application in current tokamak experimental devices.

Effect of thermal expansion on the high temperature wear resistance of Ni-20%Cr detonation spray coating on IN718 substrate

The temperature-dependent materials properties on the dry sliding wear resistance of the detonation sprayed Ni-20%Cr coating have been studied. In-situ high-temperature X-ray diffraction (HT-XRD) was used to investigate high-temperature properties such as stress relieving, recrystallization, and thermal expansion. The dry sliding wear test was performed by using a ball-on-disc tribometer by sliding velocities (0.1 m/s), varying loads (6 N and 10 N), and temperatures (25 °C and 850 °C) against alumina (Al2O3) ball. The phase evolution, thermal expansion, crystallite size, and lattice strain were determined by the Williamson-Hall method. Field emission scanning electron microscopy and a non-contact optical profilometer was used to characterize the wear scar and calculate the wear rate. The wear test results demonstrated that the as-deposited coatings coefficient of friction (CoF) and wear rate (ω) continuously decreased as the temperature increased. The primary wear mechanism changed from abrasive and surface fatigue to adhesive and oxidative wear. The impact of stress relieving, recrystallization, and forming a composite tribolayer (Cr2O3, NiO) at elevated temperatures reduced the friction and enhanced the wear resistance. The effect of stress relieving, recrystallization, thermal expansion, and oxidation on the wear resistance of the coating has been discussed with a suitable mechanism.

The Assessment of the Collision Probability of Particles in the Process of Detonation Spraying

The article discusses a technique for assessing the collision probability of particles of dissimilar materials in the process of detonation spraying of composite coatings. In consequence of different properties of initial powder materials (mass, aerodynamic resistance), quality indicators of composite coatings are determined not only with motion parameters of particles but with their mutual position in the flow of detonation products. In the case of using reactive components, interaction of molten particles in the flow can lead to chemical reactions, formation new materials on the substrate, heterogeneous structure of the coating, and deterioration its strength and adhesive properties. Preliminary quantitative assessment of the probability of collision of particles before their contact with the surface of the product affords to make a conclusion about deviation of quantitative indicators of the surface from supposed ones before full-scale tests.

Influence of Spraying Parameters on the Structure and Tribological Properties of Cr3C2-NiCr Detonation Coatings

In this work, the influence of spray parameters on the formation of the microstructure, phase composition, and the tribological properties of detonation flame sprayed coatings was studied. It was determined that the chemical composition of Cr3C2-NiCr coatings during detonation spraying depends on the degree of filling the barrel with an explosive gas mixture. The degree of filling the barrel with an explosive gas mixture at 73% leads to a decrease in the content of carbide phases, and at 57% filling of the barrel, an increase in carbide phases is observed. It is established that the decrease of the filling degree leads to the increase of hardness and wear resistance of the Cr3C2-NiCr coatings since the hardness and wear resistance of the coating material deposited at 57% is higher than at 65% and 73%; this is due to the increase in the carbide phase Cr3C2. Detonation flame sprayed Cr3C2-NiCr gradient coatings have been developed in this study, which is carried out by varying the spray parameters. It was found that in the gradient coating, Cr3C2-NiCr carbide phases gradually increase from the depth to the surface. The obtained gradient coating closer to the substrate consists of the CrNi3 phase, while the coating surface consists of CrNi3 and Cr3C2 phases.

High-Entropy Alloy Films

High-entropy alloy films have the same excellent properties as high-entropy alloys and can better realize the practical applications of high-entropy alloys. This paper takes the high-entropy alloy films as the object of discussion. The preparation process, microstructure, hardness, wear resistance and corrosion resistance of high-entropy alloy films are mainly discussed and the influence of nitridation, sputtering power, substrate temperature, substrate bias and other factors on the phase structure of alloy films is analyzed. High-entropy alloy films can be prepared using magnetron sputtering, laser cladding, pulsed laser deposition, detonation spraying, electrochemical deposition and other processes. High-entropy alloy films tend to form a solid solution and amorphous state, and their hardness is far higher than that of traditional films. Among them, the hardness of high-entropy alloy nitride films can reach the standard of superhard films. Wear resistance is usually proportional to hardness. Due to the corrosion-resistant elements and amorphous structure, some high-entropy alloy films have better corrosion resistance than stainless steel. High-entropy alloy films have shown profound development prospects in the fields of wear-resistant coatings for tools, corrosion protection, diffusion barrier and photothermal conversion coatings.