Search Results for dgs gun

This study compares the microstructure of Al 2 O 3 coatings produced by detonation gun spraying (DGS) and laser stereolithography (SLA). The SLA samples mostly consisted of alumina and voids, while the DGS-deposited alumina contained additional features such as splats, pores, cracks, and boundaries. DGS deposits were also denser with about 3% porosity compared to 8% porosity in the SLA samples. EDS analysis showed that both coatings contained only aluminum and oxygen, although additional carbon was detected in the SLA samples, indicating the presence of residual binder (resin based) material. XRD analysis revealed a mixture of α and γ-Al 2 O 3 phases in the DGS coatings, but no phase change in the SLA samples.

Oxide-bonded silicon nitride (OBSN) powders have been developed to address thermal spray problems associated with high temperatures. This paper examines how such powders perform when applied via detonation gun (DGS) and atmospheric plasma spraying (APS) with axial powder injection. All coatings were characterized using optical microscopy and X-ray diffraction with additional tests being performed on DGS coatings. For the first time, relatively dense Si3N4-rich coatings with an oxide binder phase were produced, and some of the DGS coatings were found to be sufficiently wear resistance for industrial use.

Agglomerated and sintered TiC-Ni based powders were sprayed by detonation gun spray (DGS) and high-velocity oxy-fuel (HVOF) spray processes. Influence of the binder content (20 and 27 vol.-%) and some alloying elements, such as Mo, Co and N on the coating properties were investigated. The coating structures and properties were investigated by optical microscopy, hardness measurements, X-ray diffraction analysis and by rubber-wheel abrasion wear test. It was found that alloying the hard phase with Mo and N leads to an improvement of the coating properties. Alloying of the binder phase with Co did not affect the coating properties. Porosity in the powder granules was found to beneficial in order to melt more efficiently the particles in the DGS process and especially in the HVOF process. HVOF spraying of powders with the higher binder content of 27 vol.-% was found to be advantageous for the preparation of coatings with dense microstructures and good wear resistances.

The paper reports the results of structure examination of intermetallic Fe-Al type coatings obtained by the detonation gun spraying on a C45 plain carbon steel substrate. The structure was analysed with scanning (SEM), transmission (TEM) electron microscopy techniques and electron (SAE) and X-ray diffraction methods as well as quantitative inspection of composition in microareas (EDX). Special attention was paid to the interface between the coating and the substrate analyzing particularly the substructure of the individual grains contained up to 15μm away from the substrate surface layer. The results allowed explaining the formation mechanism of the coating morphology with a contribution of intermetallic phases Fe 3 Al, FeAl, FeAl 2 and Fe 2 Al 5 as well as the ε phase taking into consideration the influence of velocity, temperature and pressure on the powder particles during the D-gun spraying. It was established that the coating produced with the DGS method had sublayer morphology of alternate flattened and partially melted grains with wide range of Al content from 39 up to 63 at.%. Partial melting of the individual powder particles brought about the appearance of the amorphous grains and subsequently columnar crystals of the Fe-Al type phases formed sequentially at the interface area coating and cold substrate surface layer material, which was essential in the mechanism of the Fe- Al coating formation. It was established, that in the area of the polycrystalline dispersive structure formed from the highly plasticized FeAl grains during D-gun spraying, complex oxide films identified as Al 2 O 3 -γ formed, serving as specific composite reinforcement in the intermetallic Fe-Al coating. A mechanism of crystallization of partially melted Fe-Al particle containing nominally 63 at.% Al was carried out in the work in an attempt to explain the formation of different sub-layers within the Fe-Al intermetallic coating at the interface 045 steel surface layer.

Three different coatings were deposited using the Detonation Gun Spraying (DGS) technology from steel powders alone, and steel powers mixed with Fe3C and SiC particles, respectively. The microstructural characteristics of these coatings were examined and the hardness of each type of coating was studied. 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. The unreinforced steel coating had the highest hardness among the three types of coatings, possibly due to a higher degree of amorphization in the coating compared to the other two samples. The microstructural observation confirmed the formation of dense coatings with a layered structure with good connectivity between layers with minimum defects and porosities in the interfacial regions.

A new class of composite powders for thermal spray on the base of recycled hardmetal powder is proposed. WC-Co hardmetal powder that is either alloyed/mixed, coated, agglomerated or cladded with binder metal - cobalt enhances the technological properties of spraying powders and enables the producing of sprayed composite coatings with double-cemented structure. The manufacturing technology of WCCo/Co composite powders composed of mixing, agglomerating, sintering and crushing was studied and characteristics of the produced spray powders by particle size, morphology of particles and specific surface area were evaluated. The experiments for deposition of coatings by high velocity spraying processes (HVS), detonation gun (DG) spraying and High Velocity Oxy-Fuel (HVOF) spraying were carried out. Comparison abrasive erosion wear tests of sprayed coatings were performed.

Hardmetal-like coatings on the base of titanium carbide as a hard phase and nickel as a metal binder were prepared from agglomerated and sintered powders by plasma spray, detonation gun spray and high-velocity oxygen-fuel spray processes. The powders used in the spray experiments were plain TiC-Ni type and alloyed (Ti,Mo)C-NiCo type powders with different binder content. The coatings were characterized by optical and scanning electron microscopy, microhardness measurements, XRD analysis and in an abrasion wear test. The results showed that the sprayability of these novel hardmetal-like powders is good in all spray processes studied and the coatings deposited were found to have dense microstructures and good properties. The XRD analysis showed that the coatings have a phase structure similar to that found in the spray powder. The amount of retained carbides in the coatings was high. Some regions in which the carbides had dissolved with the metallic binder phase during spraying were also found, especially in plasma sprayed coatings. In such microstructural regions submicron size reprecipitated carbides were detected. These were clearly detectable in detonation gun sprayed coatings. HVOF sprayed coatings were found to contain a very high content of retained carbide phase. In this process the heat effect to the material seemed to be the lowest. The wear tests clearly showed the importance of alloying the hard phase and the binder phase in order to improve the wear resistance of the coatings. All studied spray processes produced coatings with nearly similar coating wear properties.

In this investigation, binary FeAl layers are produced by detonation spraying and examined by means of microscopy and X-ray diffractometry. The examinations show that the layers have a lamellar structure consisting of FeAl and Fe 4 Al 13 phases with a small amount of alumina. It is observed that with increasing amounts of fuel gas and decreasing detonation frequency, the proportion of FeAl phases decreases and variations in microhardness throughout the coating become irregular. Paper includes a German-language abstract.

WC-Co-Cr represents an important composition for hardmetal-like coatings which is appHed when simuhaneous wear and corrosion resistance is required. In this paper five commercially available spray powders obtained by various production techniques (sintered and crushed as well as agglomerated and plasma-densified) of the composition WC-10%Co- 4%Cr have been thoroughly characterized and were sprayed by DCS, HVOF (CDS process) and APS. The microstructures of the coatings were characterized and their wear behaviour was investigated by means of an abrasion wear test. For the best of these powders the wear resistance was nearly equal for the DGS and HVOF coatings. Other powders show significant differences with respect to their processabilities in these spray processes. APS coatings from all powders, obtained with an Ar/H2 plasma showed inferior microstructures and significant lower wear resistance. The spray powder compositions, grain sizes and structures were found to determine the processability of the powders and the microstructure and properties of the coatings. COMPOSITE MATERIALS of the type hard phase - metallic binder with WC and CoCr as constituents are widely used for the preparation of hardmetal-like coatings. The chromium addition to the metallic binder is thought to improve its corrosion resistance in comparison with pure WC-Co. This has led to many applications of WC-CoCr coatings where simultaneous wear and corrosion resistance is required. Despite of its significant practical importance only a limited number of publications is devoted to detailed questions of structure and properties of WC-CoCr coatings (1-3). In some comparative studies such coatings have been investigated together with WC-Co and Cr3C2-NiCr coatings (4-8). However, systematic investigations of spray powder compositions and morphologies as well as investigations of the influence of different thermal spray processes on coating structures and properties which have repeatedly been provided for WC-Co (for example (9, 10)) are missing for WC-CoCr. In this paper a short survey of literature on the phase relationships in the WC-CoCr system and the effect of chromium additions on the properties of sintered parts and thermally sprayed coatings compared to WC-Co is given. In the experimental part a systematic study of the influence of the preparation process on composition and morphology of commercially available WC-10%Co-4%Cr spray powders was provided. These powders have been sprayed by DGS, HVOF and APS and the microstructure and basic properties of the coatings have been studied.

It is difficult for engineers and scientists to remain up to date on the wide variety of surface engineering technologies available for product and process design, to solve maintenance problems, etc. This paper provides a brief overview of several of the major types of surface processes and resulting coatings or other surface treatments. It is intended only to provide an elementary introduction to serve as a background for further inquiry by the reader or to assist those not familiar with a given field to more easily understand other presentations in this conference session. The technologies considered include thermal spray, physical vapor deposition, and chemical vapor deposition.

TiC-based coatings sprayed by different processes, such as detonation gun spraying, high velocity oxy-fuel spraying, atmospheric plasma spraying (APS), and vacuum plasma spraying, using agglomerated and sintered powders have been actively developed over the years. This development is based on the high technical and engineering potential of the hard phase TiC. This paper describes the results of basic studies of the APS for various alloying steps in the production of TiC base coatings from agglomerated and sintered powders as well as the results of the application of APS coatings on piston rings. Paper includes a German-language abstract.

The surfaces of machine components can be effectively protected against wear by highly resistant hardmetal-like coatings, such as WC-Co and Cr 3 C 2 -NiCr, deposited by different thermal spray processes. These composite materials are characterized by the presence of hard carbide particles embedded in a ductile metal binder matrix which have also found many applications as sintered parts (cutting tools, wear resistant parts, mining drills and others) obtained by a powder metallurgy route. Conclusions on the potentials of the different systems for coating applications can be made on the base of experiences and fundamental research from sintered hardmetals. In this paper a comparison of the properties of sintered parts and thermally sprayed coatings of the WC-Co, Cr 3 C 2 -NiCr and (Ti,Mo)C-NiCo systems is given. The structure and properties of the coatings depend strongly on the technology of spray powder preparation, the combination of spray process temperature and particle velocity, and other spray process parameters. It is shown that the TiC-Ni based system can be significantly improved by alloying. This makes the system suitable for coating applications where simultaneous high wear and corrosion resistance in combination with high temperature stability are required. This system can partially substitute the commercially introduced systems but has also the potential to explore new applications.

The paper is devoted to gaseous detonation spraying and presents the state of current knowledge, as well as the following research and development needs: gaseous detonation as spraying heat source; operation cycle of detonation guns and its possible versions; operating frequency; impulse jet formation; basic detonation guns design concepts, as fuel and oxidant types, features of barrel design, predetonation distance control, valved and valveless detonation guns concepts, etc.; gas dynamic characteristics of detonation spraying.

This paper provides a short summary of the information that can be found in the literature on the preparation and structure of titanium carbide (TiC) wettable powders. From the work that has been done, it can be concluded that TiC-based coatings can be tailored for applications where complex stress profiles are encountered. Paper includes a German-language abstract.

300M steel is one of most important aerial materials, which can be used for landing gear and flap & slat track. Some surface engineering technologies are needed to be adopted on its surface, because of its bad corrosion performance. WC10Co4Cr Coatings by high velocity oxygen-fuel spray processing (HVOF) is an environmental friendly method for this protection. In this paper, WC10Co4Cr coatings were prepared on 300M by optimized HVOF processing. And their corrosion performance has been estimated by neutral salt fog test, according with ASTM B117. The results indicate that the porosity gets larger and the hardness gets higher for the dissolution of bonding phases after the test. And for the optimized coatings, there are no corrosion products in the surface and interface between the coating and 300M steel, after 2000 hours ASTM B117 test. So the coatings have a good corrosion performance.

The author carried out in 2003 a multiclient survey and research covering thermal spraying industry in China. This work mainly focus on the productive level and scale of thermal spraying equipment and materials, application and coating job shop, R&D in universities and institutes as well as the develop trends of thermal spraying industry in China. This presentation intends to provide general pictures on thermal spraying industry in China, by offering data and analysis, forecasts the future of thermal spraying in China.

This study investigates the influence of component geometry, particularly the outer radius of curved surfaces, on the hardness and porosity of HVOF-sprayed WC-Co coatings as well as the deposition rate. A fine agglomerated and sintered WC-12Co powder of spherical shape was sprayed on steel substrates. Process parameters were held constant, while the radius of curvature was varied between 5 and 40 mm. The results show that HVOF spraying is better for depositing fine particles on curved surfaces than other spray processes, although the deposition rate decreases compared to flat substrates.

The mathematical model intended for modeling of the acceleration, heating, and melting of alloyed cast iron particles into plasma jet is presented. Comparison of mathematical modelling and experimental measurement results showed fairly good agreement.

Computer simulations of thermal spray coating processes can accelerate the development of new products by minimizing the need for prototypes. An important aim of these simulations is the calculation of the coating distribution on the surface of a given workpiece with respect to a given movement path of the spray gun. In this paper, a novel approach for computing coating distribution on arbitrarily complex freeform surfaces is presented. In contrast to approaches that implement symmetric deposition models, the presented concept is based on a rotationally asymmetric model, making it particularly well suited for wire arc spraying as turbulences caused by electrodes in the gas flow often result in asymmetric coating distributions. In order to obtain the required knowledge base to derive the deposition model and verify the simulation, basic experiments were made. The simulation concept and experimental setup are presented in the paper along with the results.

In result of the spray process normally a phase change from α-alumina (corundum) in the feedstock powder to predominantly α-alumina in the coating takes place. This is a well known but often neglected fact in the preparation and use of alumina coatings. This is of special interest since the high usage properties of thermally sprayed alumina coatings are generally derived from sintered alumina ceramics which consist of corundum. It is expected that the prevention of this phase transformation will significantly change the mechanical, electrical and other properties of thermally sprayed alumina coatings. There is controversial information about the possibility of stabilization of α-alumina by additions of chromia in the literature. In this work the stabilization using different spray processes (water stabilized plasma WSP, gas stabilized plasma APS and HVOF) was studied. Mechanical mixtures of alumina and chromia were used, as well as pre-alloyed powders consisting of solid solutions. The coatings were studied by X-ray diffraction and metallographic cross-sections. It was shown that in the case of the mechanically mixed powders the stabilization predominantly depends on the applied spray process. The stabilization by use of the WSP process was confirmed.