Jet Impingement Erosion Research Articles

Optimisation and analysis of jet impingement erosion behaviour of composite titanium based ENi-P coated naval steel (AH36)

ABSTRACT This paper aims to address the impact of jet impingement on nano titanium-based ENi-P composite coatings deposited through electroless deposition on AH36 steel through Taguchi design of experiments. L9 Taguchi DOE was utilised to synthesise nine coatings by varying the four process parameter combinations suggested by the technique. Jet impingement combined with AFS 50/70 quartz sand erosion experimental run was conducted on the acidic, alkaline and nine ENi-P-TiO2 composite coatings administered through a waterjet erosion tester. The influence of C14-SB type Zwitterionic surfactant and nano TiO2 were discussed along with temperature and bath pH to achieve better resistance against the jet impingement on the surface of the coatings. Analysis of variance, the S/N ratio, and interaction plots were used to determine the optimal bath input parameters to deliver the least weight loss from the erosive environment and identify its use in the marine environment. The proposed optimal coating was validated using a confirmation test, and the weight loss was reduced by more than 35% compared to the initial condition parameter (A2B2C2D2). In addition to mechanical properties, the quality of the deposits was analysed through morphological and chemical composition probed through scanning electron microscope, energy dispersive X-Ray analysis and powder X-Ray diffraction methods. As a result, the Composite Modified Resilience (CMR) value of ENi-P-TiO2 optimal coating was improved by over 41.17%, and its corresponding weight loss was reduced to 35% compared to the initial condition. This experiment paves the way for further study on electroless deposits and their characteristics on AH36 steel generally used for shipbuilding in commercial ships, naval, and marine associated defence applications.

Optimization of Jet Impingement Erosion Process of Alumina-Titania coated stainless steels

The mineral processing industries depend on conveying feed stocks in slurry form. Slurries erode the carriers as well as the pumps which are used in the process. Material loss due to erosion is a serious problem in transporting solid liquid mixture. The pump impellers are generally made of stainless steel. The efficiency of the stainless steel impellers decreases due to erosion even though the pump continues to work. These impellers are damaged or lose its efficiency roughly during 250–300 h of operation. Stainless steel materials used for impellers are taken to the required dimension and are given Alumina-Titania coating using detonation spray process. The thickness of the coating is 250 µm. The coated specimen is mounted in the work piece holder and subjected to erosion test using water Jet erosion tester.The parameters that are varied are exposure time, velocity of the jet and angle of impingement. Through this study it was found out that the most influencing factors of Liquid impact erosion are impact Angle and exposure time. It is observed that maximum erosion takes place when the impact angle is 90 degrees The SEM images reveal that the material removal takes place due to chipping and micro cutting. This occurs when the angle of impingement is 90° and the velocity of impingement is reasonably higher.

Cavitation Erosion and Jet Impingement Erosion Behavior of the NiTi Coating Produced by Air Plasma Spraying

Cavitation erosion and jet impingement erosion can result in a great loss of materials. NiTi alloy is a very promising candidate to acquire cavitation erosion resistance and jet impingement erosion resistance because of its superelasticity. Due to the high cost and poor workability of NiTi alloy, many people tried to overcome such drawbacks by preparing NiTi coatings on the basis of deteriorating the good properties as little as possible. From the aspect of the application of NiTi coating, the erosion resistance should be evaluated comprehensively. One of these evaluations involves the comparison of cavitation erosion resistance and jet impingement erosion resistance of NiTi. This evaluation has not been made thus far. Thus, in this study, the NiTi coating was prepared by air plasma spraying (APS) using pre-alloyed NiTi powder. Its microstructure, chemical composition and phase transformation were identified. Cavitation erosion behavior and jet impingement erosion behavior of the as-sprayed NiTi coating were compared. The results showed that the coating exhibited better jet impingement erosion resistance than cavitation erosion resistance. This was attributed to the oxides, impurities, cracks and pores that existed in the coating, whose effects on deteriorating the cavitation erosion were far greater than those worsening the jet impingement erosion.

The Effect of pH on Slurry Erosion–Corrosion of Tungsten Carbide Overlays Alloyed with Ru

The aim of the study was to determine the effect of Ru additions to WC-Fe overlays when exposed to low pH slurry erosion conditions. These overlays were applied through Plasma Transferred Arc, and the original bulk Ru powder concentrations varied from 0.5 to 5 wt.%. A slurry jet impingement erosion–corrosion test rig was used to evaluate wear, and electrochemical measurements were performed to characterize the corrosion properties. The slurry mixtures contained silica sand and synthetic mine water. The pH was varied between 3 and 6.5 for the slurry erosion tests and lowered further for the corrosion characterization. Samples were examined optically and with a scanning electron microscope using energy-dispersive x-ray spectroscopy. X-ray diffraction analysis was used to determine the phases present. For the slurry erosion–corrosion results at the pH of 6.5, addition of Ru did not show a decrease in erosion–corrosion rates. However, when the pH was decreased to 3, by the addition of HCl, Ru improved the resistance. From the electrochemistry, it was also clear that Ru additions improved the corrosion resistance, but more than 1 wt.% Ru was required. At very low pH levels, the presence of Ru was not able to prevent corrosion.

Evaluation of Cathodic Arc Deposited Thick CrAlSiN Coatings by Erosion Test

CrAlSiN with thickness up to 16 μm was deposited on tungsten carbide via multi-deposition process by cathode arc deposition technique. Scratch and water-sand jet impingement erosion tests were carried out to evaluate the adhesion by determining the worn surface of the coatings. Results showed that the failure mode of the adhesion can be concluded that the weak bond of each CrAlSiN layer as compared to the strong bond between the coating and substrate. The average surface roughness of the coatings before the erosion test was about the same level. After the erosion test of 30 minutes, the eroded CrAlSiN coatings exhibited improved average surface roughness as compared to the original CrAlSiN coatings. Further increasing the erosion up to 60 minutes, the wear and minor peeling of the CrAlSiN coating between each layer was observed. A further research to improve the bond strength between each layer was needed.

Cavitation erosion and jet impingement erosion mechanism of cold sprayed Ni–Al2O3 coating

Abstract A composite coating was deposited on Inconel 600 substrate by cold spray method using pure Ni powder (60 wt.%) blended with α-Al2O3 (40 wt.%) as feedstock. It is expected to be applied to repair the bellows eroded by the liquid droplet erosion (LDE). Microstructure of the coating was observed using optical microscope (OM) and scanning electron microscopy (SEM). Microhardness of the coating was determined by Vickers hardness tester. Cavitation erosion (CE) experiments were carried out in the distilled water. Jet impingement erosion (JIE) experiments were performed in slurry containing 1 wt.% quartz particle with the flow velocity of 15 m/s at impingement angles of 30°, 60° and 90°, respectively. Cumulative mass loss vs. testing time was used to evaluate the erosion rate of the coating. The erosion mechanism was analyzed by OM, SEM, X-ray diffraction (XRD) and the microhardness measurement. The results show that the composite coating has compact microstructure and relatively high hardness. The resistance to CE of the coating is not as good as that of Inconel 600 substrate due to the weak bonds of the Al2O3 particles. However, the results of the JIE test indicate that the slurry erosion resistance of the coating is better than that of Inconel 600 at the impact angles of 30° and 60°, but not at the normal impact angle.

Comparison of Inconel 625 and Inconel 600 in resistance to cavitation erosion and jet impingement erosion

Liquid droplet erosion (LDE), which often occurs in bellows made of nickel-based alloys, threatens the security operation of the nuclear power plant. As the candidate materials of the bellows, Inconel 600 and Inconel 625 were both tested for resistance to cavitation erosion (CE) and jet impingement erosion (JIE) through vibratory cavitation equipment and a jet apparatus for erosion-corrosion. Cumulative mass loss vs. exposure time was used to evaluate the erosion rate of the two alloys. The surface and cross-sectional morphologies before and after the erosion tests were observed by scanning electron microscopy (SEM), the inclusions were analyzed by an energy dispersive spectroscopy (EDS), and the surface roughness was also measured by surface roughness tester to illustrate the evolution of erosion process. The results show that the cumulative mass loss of CE of Inconel 625 is about 1/6 that of Inconel 600 and the CE incubation period of the Inconel 625 is 4 times as long as that of the Inconel 600. The micro-morphology evolution of CE process illustrates that the twinning and hardness of the Inconel 625 plays a significant role in CE. In addition, the cumulative mass loss of JIE of Inconel 625 is about 2/3 that of Inconel 600 at impacting angle of 90°, and almost equal to that of the Inconel 600 at impacting angle of 30°. Overall, the resistance to CE and JIE of Inconel 625 is much superior to that of Inconel 600.

Tribology of thermal sprayed WC–Co coatings

This paper looks at the tribology of thermal sprayed WC–Co based coatings and covers the high energy air–sand erosion resistance and slurry jet impingement erosion performance, dry and wet sliding tribology of thermal spray WC–Co based coatings as well as the abrasion and abrasion–corrosion of these coatings. The tribological and tribo-corrosion performance of the coatings will be related to their mechanical and corrosion properties as well as deposition parameters, microstructure and actual composition. For example, the anisotropic microstructure of thermally sprayed WC–Co–Cr coatings, in particular the low fracture toughness in a direction parallel to the substrate, has been observed to affect the nature of crack formation under 200 μJ air–solid particle erosion conditions. Voids and occasionally other microstructural features (i.e., cobalt lakes, splat boundaries, interfacial inclusions) in the coating act as crack initiation sites. The erosion rate was dominated by cracks within 5 μm of the surface and was relatively insensitive to total length of cracks, showing a near-surface damage front controls the erosion rate and this region is coincident with the region of maximum shear stress induced by erodent impacts. Optimisation of the deposition parameters of HVOF 86WC–10Co–4Cr coatings show an improvement in erosion resistance of more than 50% over the conventional D-gun applied coating of identical nominal composition. The variation in the slurry erosion performance of the thermally sprayed coatings is also linked to directional fracture toughness and crack propagation paths which are influenced by the presence of pores, inhomogeneous carbide distributions and substrate grit blast remnants. The influence of slurry jet angle is more pronounced under 0.4 μJ energy conditions where maximum erosion occurred at 90° and the minimum at 30° in contrast to 7 μJ slurry erosion rates which were independent of jet angle. This reflects the lower levels of fluctuating stresses imparted to the coating during low energy slurry impacts leading to the impact angle having a greater effect on sub critical crack growth rate than for higher energy conditions. The abrasion resistance of these coatings was found comparable to sintered cermets of the same composition. The synergistic effects between micro and macro abrasion and corrosion for detonation gun (D-gun) sprayed WC–10Co–4Cr coatings are shown to be significant and depend on the environment. The size effect of the abradant relative to the microstructure and splat size is important as well as the propensity for the various phases to passivate to control corrosion levels. Comparisons between exposed and freshly polished coating surfaces in strong NaOH solutions (pH 11) show that significantly lower wear rates were seen for the exposed surface due to a negative wear–corrosion synergy due to selective phase removal and the effects of localised passivation. Dry and wet sliding wear resistance of these coatings is shown to be high (wear rates of 10−16–10−18 m3/Nm) with modest coefficient of friction levels between 0.2 and 0.5. The presence of oxides on the binder phases appears to influence the friction and wear levels. Wear appears to be by carbide ejection and/or by tribo-chemical processes.

Machining of nickel-base, Inconel 718, alloy with ceramic tools under finishing conditions with various coolant supply pressures

Machining of Inconel 718 with whisker reinforced ceramic tool gave better performance in terms of tool life under high-pressure coolant supplies up to 15 MPa compared to conventional coolant supplies. The use of 15 MPa coolant supply pressure tend to suppress notching during machining thus improving tool life, while the use of higher coolant supply pressure of 20.3 MPa did not show improvement in tool life due probably to accelerated notch wear caused by water jet impingement erosion. Cutting forces decreased with increasing coolant supply pressure due to improved cooling and lubrication at the cutting interface as well as effective chip segmentation ensured by the momentum of the coolant jet. Surface roughness generated were well below the rejection criteria. This can be attributed to the round shape of the insert which tend to encourage smearing of the machined surface with minimum damage. Microstructure analysis of the machined surfaces show evidence of plastic deformation and hardening of the top layer up to 0.15 mm beneath the machined surface as a result of increase in dislocation density.

An experimental study to corelate water jet impingement erosion resistance and properties of metallic materials and coatings

This paper describes the water jet impingement erosion characteristics of titanium alloy (Ti 6Al 4V), Hadfield steel, laser hardened, plasma nitrided and pack borided 12Cr steel along with most commonly used steels in hydro turbines. Round samples as per ASTM G73-98 were tested for water jet impingement erosion study. While testing, in the incubation period, plasma nitrided and pack borided 12Cr steel performed much better than 12Cr and 13Cr4Ni steels. Plasma nitrided 12Cr steel performed much better than pack borided 12Cr steel. This is due to the integrity of plasma nitrided layers and their ability to absorb shocks due to jet impingement. During incubation as well as in the long run, Hadfield steel and laser hardened 12Cr steel performed exceptionally well followed by 17Cr4Ni ‘PH’ steel. Based on this experimental study, a suitable criterion based on ultimate resilience (UR) for metallic materials and a composite modified resilience (CMR) for hard metallic coatings has been discussed. Water jet impingement erosion test results along with the mechanical properties of materials and coatings, and their scanning electron microstructural details are reported in this paper.

Fractal analysis of eroded surfaces by digital image processing

Jet impingement erosion test rig has been used to erode titanium alloy specimens (Ti–4Al–4V). Eroded surface profiles have been obtained by vertical sectioning method for light microscopy observation. Mixed fractals have been measured from profile images by a digital image processing and analysis technique. The use of this technique allows glimpsing a quantitative correlation among material properties, fractal surface topography and erosion phenomena.

The sand erosion performance of coatings

This paper reviews studies of the performance of polymeric, metallic and ceramic including diamond coatings on steel and ceramic substrates when subjected to water–sand jet impingement erosion conditions. The coatings tested have been deposited by the thermal spray, electroless plating, PVD and CVD routes. The erosion conditions covered include sand impact velocities between 10 and 30 m/s with sand sizes 60–235 μm and at jet impingement angles of 30° and 90°. Tests compared the performance of the substrate material carbon steel AISI 1020 with the various polymeric, metallic and ceramic coatings. Coating and substrate erosion rates are plotted against mean particle impact energy, E k or E kV p 0.5 allowing easy surface selection once the erosion conditions of an application are known. The effect of jet impingement on the erosion resistance of selected coatings is presented. As with bulk materials, the slurry jet impingement angle and mean E k must be considered in coating selection. Of the softer coatings tested the flexible polyurethane coatings seem to have promise for future use in fluid-borne sand particle erosion environments. Pure epoxy coatings show typical brittle erosion behaviour, with fusion-bonded epoxy having mixed ductile and brittle behaviour and glass fibre reinforced epoxy showing strong ductile behaviour. CVD deposited coatings of either boron carbide or diamond are the most resistant surfaces tested and outperform bulk ceramics such as silicon carbide by orders of magnitude for E k <8 μJ and 90° jet impingement angle. Areas requiring further research to allow accurate prediction of coating life are highlighted.

Design and performance of a high velocity air–sand jet impingement erosion facility

This paper describes the design, construction and capabilities of a high velocity air–sand erosion rig. It has been designed with the aid of computational fluid dynamics to approximately simulate the erosion conditions often experienced by subsea choke valves used in the offshore oil industry. It has also been designed to evaluate the erosion performance of CVD diamond coatings at sonic velocity. The rig is of the gas-blast design in which solid particles, typically sand 60–660 μm in size, are injected into a high velocity air stream and accelerated down a 16-mm-diameter tube, 1 m in length, before striking the sample under test. Tests can be carried out with particle velocities of up to 340 m/s under a wide range of sand fluxes, impact angles and standoff distances. The results of pressure, velocity and sand flux calibration work are described. In addition, preliminary experimental data on tests carried out on mild steel, bulk and sprayed tungsten carbide are also presented. The flexibility of the air–sand rig allows the erosion behaviour of materials to be studied under a wide range of conditions.