Solid Particle Erosion Tests Research Articles

Influence of Plasma Intensity on Wear and Erosion Resistance of Conventional and Nanometric WC-Co Coatings Deposited by APS

The effects of plasma intensity and powder particle size on wear and erosion resistance have been evaluated for WC-12 wt.%Co coatings deposited by Air Plasma Spraying. Coatings were deposited from micrometric and nanostructured powders. SEM and XRD characterization showed the presence of WC, W2C, W, and an amorphous Co-rich matrix. The performance of the different coatings was compared in sliding wear tests (ball-on-disk), under dry friction conditions. Wear debris and tracks were analyzed by SEM. The debris generated during the test was found to have a great influence on the sliding properties. Wear follows a “three-body abrasive mechanism” and is dominated by coating spallation because of sub-surface cracking. In order to evaluate erosion behavior, solid particle erosion tests were conducted. Eroded coatings were analyzed by SEM, and erosion mainly occurs by a “cracking and chipping mechanism.” The study shows that wear and erosion behavior is strongly affected by plasma arc intensity.

Microstructure and tribological performance of nanocomposite Ti–Si–C–N coatings deposited using hexamethyldisilazane precursor

Thick nanocomposite Ti–Si–C–N coatings (20–30 μm) were deposited on Ti–6Al–4V substrate by magnetron sputtering of Ti in a gas mixture of Ar, N2, and hexamethyldisilazane (HMDSN) under various deposition conditions. Microstructure and composition of the coatings were studied using scanning electron microscopy, x-ray diffraction, and energy dispersive x-ray spectroscopy, while the mechanical and tribological properties of these coatings were studied using Rc indentation, and micro- and nanoindentations, solid particle erosion testing, and ball-on-disk wear testing. It has been observed that the Si concentration of these coatings is varied from 0% (TiN) to 15% (Ti–Si–C–N), while the structure of these coatings is similar to the nanocomposite Ti–Si–N coatings and consists of nanocrystalline B1 structured Ti(C,N) in an amorphous matrix of SiCxNy with the grain size of 5−>100 nm, depending on the coating preparation process. These coatings exhibit excellent adhesion when subjected to Rc indentation tests. The microhardness of these coatings varies from 1200 to 3400 HV25, while the nanohardness varies from 10 to 26 GPa. Both the microhardness and nanohardness are slightly lower than those of similar coatings prepared using trimethylsilane. However, the erosion test using a microsand erosion tester at both 30° and 90° incident angles shows that these coatings have very high erosion resistance and up to a few hundred times of improvement has been observed. These coatings also exhibit very high resistance to sliding wear with a low coefficient of friction of about 0.2 in dry sliding. There are a few advantages of using the HMDSN precursor to prepare the Ti–Si–C–N coatings over conventional magnetron sputtered deposition of Ti–Si–N coatings including composition uniformity, precursor handling safety, and high deposition rate. The coatings can be applied to protect gas turbine compressor blades from solid particle erosion and steam turbine blades from liquid droplet erosion, as well as other mechanical components that experience severe abrasion. These coatings may also be used in areas where both high wear resistance and low friction are required.

Characterisation of HVOF sprayed Cr3C2-50(Ni20Cr) coating and the influence of binder properties on solid particle erosion behaviour

Abstract The coating Cr 3 C 2 with 50 wt.% Ni20Cr deposited by high velocity oxy-fuel (HVOF) spray process was characterized in detail to investigate the effect of annealing on the solid particle erosion behaviour and understand the influence of the binder properties. Systematic characterization of the coating was carried out using electron microscopy (scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron probe microanalysis (EPMA)), X-ray diffraction (XRD), microindentation and nanoindentation techniques. The solid particle erosion tests were done on the as-sprayed coating and coatings annealed at 400 °C, 600 °C and 800 °C using silica erodent particles. The coefficient of restitution of the coated samples was also measured by WC ball impact tests to simulate dynamic impacts. The as-sprayed coating consisted of primary carbides and binder that was a mixture of amorphous and nanocrystalline phases. Annealing leads to recrystallisation of binder phase and precipitation of secondary carbides. The coating hardness and binder ductility change with annealing temperature. The erosion resistance improves with annealing up to 600 °C. In the as-sprayed coating, the amorphous phase, inter-splat boundaries and the elastic rebound characteristics affect the erosion response. While in the case of the coating annealed at 600 °C, the presence of ductile crystalline binder, fine carbide precipitates and embedment of erodent particles together improve solid particle erosion resistance.

Nanotechnology Coatings for Erosion Protection of Turbine Components

Solid particle erosion (SPE) and liquid droplet erosion (LDE) cause severe damage to turbine components and lead to premature failures, business loss, and repair costs to power plant owners and operators. Under a program funded by the Electric Power Research Institute, TurboMet International and Southwest Research Institute (SRI) have developed hard erosion resistant nanocoatings and have conducted evaluation tests. These coatings are targeted for application in steam and gas turbines to mitigate the adverse effects of SPE and LDE on rotating blades and stationary vanes. Based on a thorough study of the available information, the most promising coatings, such as nanostructured titanium silicon carbonitride (TiSiCN), titanium nitride (TiN), and multilayered nanocoatings, were selected. State-of-the-art nanotechnology coating facilities at SwRI were used to develop the coatings. The plasma enhanced magnetron sputtering method was used to apply these coatings on various substrates. Ti–6Al–4V, 12Cr, 17-4PH, and custom 450 stainless steel substrates were selected based on the current alloys used in gas turbine compressors and steam turbine blades and vanes. Coatings with up to 30μm thickness have been deposited on small test coupons. Initial screening tests on coated coupons by solid particle erosion testing indicate that these coatings have excellent erosion resistance by a factor of 20 over the bare substrate. Properties of the coating, such as modulus, hardness, microstructural conditions including the interface, and bond strength, were determined. Tensile and high-cycle fatigue tests on coated and uncoated specimens indicate that the presence of the coatings has no negative effects but has a positive influence on the high-cycle fatigue strength at zero and high mean stresses.

Study of Erosion Behaviour of Conventional and Nanostructured WC-12Co Coatings Sprayed by Atmospheric Plasma

Thermal sprayed WC-Co coatings are used extensively to enhance the wear resistance of a wide range of engineering components. In this paper, erosive resistance of plasma atmospheric sprayed WC-12Co coatings has been evaluated. Solid particle erosion tests were conducted on these coatings at different angles of impact with silica and alumina abrasives of size 250 µm. Coatings have been deposited by using micrometric and nanometric agglomerated powders, employing H2 and He as plasmogen gas. In order to determine the erosion regime (ductile or brittle), the influence of impact angle on the erosion rate has been studied. Optical microscope and FESEM have been used to analyze the eroded surface. The influence of the plasmogen gas and the powder employed on the erosive behaviour of the coating has been evaluated. An attempt to connect the erosive behaviour with mechanical properties and microstructure has been made. Hardness has been determined by means of several measurements of Vickers microhardness; fracture toughness has been estimated through indentation method. Identification of phases has been made by means of X Ray diffraction.

Analytical model of particle interference effects in divergent erosive jets

Abstract An analytical model that describes the interference, due to collisions between an incident diverging axi-symmetric jet of spherical particles, and those rebounding from a flat surface oriented perpendicular to the jet axis (i.e., normal incidence), is presented. The model can accommodate non-uniform incident particle velocity and spatial distribution, variation in particle spacing along the jet axis, and non-elastic frictional impact kinematics. The model can be used to estimate interference effects at high flux, and to obtain the critical flux below which a given level of particle interference will occur in a solid particle erosion test. Because the equations that predict the level of interference can be solved in closed form, with the exception of an integral which must be solved numerically, implementation in erosion models is also possible. For the case of an incident jet typically used in abrasive jet micromachining applications, the model is validated against an existing computer model for a wide variety of conditions, with excellent agreement.

Solid particle erosion studies on biomorphic Si/SiC ceramic composites

Solid particle erosion tests were conducted on four different types of silicon carbide ceramic composites. The composites are cotton fabric based Si/SiC with and without chemical vapour infiltration, fine teak wood powder based Si/SiC and coarse teak wood powder based Si/SiC. The erodents used are angular SiC particles of average size 80, 250 and 450 μm. The velocities with which particles impacted on the target materials were varied from 20 to 50 m/s. Similarly the angle of impact was varied from 20° to 90°. Scanning electron microscopic observations on the eroded surface show brittle and cleavage like fracture. Fine teak wood powder based Si/SiC ceramic shows better erosion resistance than the other ceramics. Homogenous distribution of SiC grains with the presence of very fine grains of silicon and carbon is responsible for the improved erosion resistance. The higher erosion rate in cotton fabric based SiC arises from its microstructure. Here, the free carbon and free silicon grains are large in size and the SiC phase has very low hardness as compared to the erodent.

Improving Erosion Resistance of Polymer Reinforced Composites

This article reports on solid particle erosion tests performed on glass fiber reinforced polyphenylene sulphide (PPS) for use on an all-composite ice-protection system for aircraft structures. The idea was introduced to use a metal mesh as a convenient way of toughening the surface layer thereby increasing erosion resistance. The erosion rates of the composites were evaluated at different impingement angles and with different erodent particle size. An aircraft-grade aluminium sheet was also used to provide a comparison for the composites. It was found that the erosion rate of the composites drastically reduced upon the introduction of an impregnated mesh onto the surface of the baseline glass/PPS laminate, to values similar to that of the aluminium sheet. In addition, the erosion rate was found to be dependent not only on the volume fraction of the matrix on the surface, but also the properties of the metal used for the mesh. The solution to use a metal mesh was shown to have multifunctional uses for composite based ice-protection system.

Influence of erodent particle types on solid particle erosion of polyphenylene sulphide composite under low particle speed

AbstractThe influence of erodent particle types on solid particle erosion of randomly oriented short glass fiber and mineral particle reinforced polyphenylene sulphide (PPS) was investigated. The solid particle erosion studies were carried out using low speed solid particle erosion test rig with 150 to 212‐μm brown fused aluminum oxide (Al2O3), 150 to 200‐μm silica sand and 150 to 250‐μm glass bead. Glass bead eroding particles appear spherical in shape whereas aluminum oxide and silica sand eroding particles have sharp and angular edges. The erosion tests were conducted at six different contact angles of 15, 30, 45, 60, 75, and 90°, respectively. The results showed a strong dependence of the eroding particle types on the erosive wear behavior of PPS composite. The peak erosion rate occurred at 45° contact angle for silica sand eroding particles while the peak erosion rate occurred at 30° contact angle for aluminum oxide and glass bead particles. The morphologies of eroded surfaces were characterized by the scanning electron microscopy. In case of aluminum oxide and silica sand, the erosive wear mechanism occurs firstly by the erosion of matrix, followed by the fracture of un‐supported fibers and their detachment; however, the erosive wear mechanism occurs different for glass bead particles. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers

Effect of microstructure on the erosion resistance of Cr–Si–N coatings

Erosion by solid particle impact can cause severe damage to critical components of airplanes, helicopters and other systems, thus affecting their overall performance, cost and most notably safety. In our search for novel high performance erosion resistant coatings, we studied Cr–Si–N coatings (8 to 13 μm thick) deposited on AISI 410 stainless steel substrates by DC reactive dual-magnetron sputtering using Cr and Si targets. Microstructure, composition and the mechanical properties were studied as a function of the silicon content ( C Si) using XRD, ERD-TOF, and the depth sensing and Vickers indentation techniques. A maximum hardness of 26.6 GPa was found for Cr–Si–N with C Si = 6.7 at.%, while that of pure CrN was 19.4 GPa. Solid particle erosion (SPE) tests were performed according to the ASTM G76 standard on a test rig developed by our laboratory: Al 2O 3 particles with an average diameter of 50 μm were projected onto the coating surface, with a mean velocity of 70 m/s and a normal (90°) incidence angle. The 90° erosion rate of Cr–Si–N with C Si = 11.6 at.% was found to be 5.2 × 10 − 3 mg/g, one order of magnitude lower than that of pure CrN and 20 times lower than that of the substrate. We specifically discuss the SPE behavior of the Cr–Si–N coatings with respect to their mechanical (hardness, reduced Young's modulus and toughness) and microstructural (texture and morphology) characteristics.

Solid-particle erosion behavior of high-performance thermoplastic polymers

Solid-particle erosion tests were carried out to study the effect of matrix material, impact angle, and impact velocity on the erosion behavior of seven types of thermoplastic neat polymers (i.e., polyetherimide, polyetheretherketone, polyetherketone, polyphenylene sulfide, polyethersulfone, polysulfone, and ultrahigh molecular weight polyethylene). Steady-state erosion rates of these polymers have been evaluated at different impact angles (15–90°) and impact velocities (25–66 m/s). Silica sand of particle size 200 ± 50 μm was used as the erodent. These polymers have exhibited maximum erosion rate (E max) at 30° impact angle indicating ductile erosion behavior. Some of these polymers have shown an incubation behavior at lower impact velocities for an impact angle of 90°. Correlations among steady-state erosion rate and mechanical properties and glass transition temperature (T g) were established. Morphology of eroded surfaces was examined using scanning electron microscopy and possible wear mechanisms were discussed.

Solid Particle Erosion Behavior of FRPs with Prior Impact Damage

Experiments have been carried out to study the solid particle erosion of FRPs with prior impact damage. Two kinds of FRPs i.e., the epoxy resin reinforced by aramid fibers (AR/EP) and poly p-phenylene-benzobisoxazole fibers (PBO/EP) are used. The AR/EP and PBO/EP laminates with the same layout structure of 12-ply and [0°/90°]6s have the volume fractions of 55.8 and 53.8%, respectively. Prior to erosion tests, the test materials are impact damaged by the projectile shot from an air gun. The interlaminar shearing stress (ILSS) is obtained as a measure for impact damage of the FRPs. Solid particle erosion tests are then performed for the FRPs after they are damaged with a spherical projectile with the velocity of 130 m/s. The test results show that the erosion rates of the FRPs with prior impact damage are less than those of the virgin materials. Less erosion resistance of the FRPs with prior impact damage may be because the FRPs with prior impact damage have a lot of transverse cracks and delaminations, which absorb the kinetic energy of the solid particles used in the erosion tests.

Solid-particle erosion of tungsten carbide/cobalt cermet and hardened 440C stainless steel—A comparison

Solid-particle erosion tests were conducted on hardened AISI 440C stainless steel and a cermet that consisted of ≈90 vol.% submicrometer WC embedded in ≈10 vol.% Co. Angular Al 2O 3 abrasives were used as the erodent. Experimental variables were: angle of impact = 20°, 50°, or 90°; erodent velocity = 60 or 120 m/s; erodent nominal diameter = 63 or 143 μm. For all test conditions, the stainless steel eroded faster than the cermet. Analysis of weight-loss data and examination of eroded surfaces by scanning electron microscopy indicated that the erosion mechanisms were similar for the two hard materials. Both exhibited significant plasticity when impacted, but the stainless steel's response to impact appeared to have been more ductile in nature.

Solid particle erosion resistance of thermally sprayed functionally graded coatings for polymer matrix composites

Thermally sprayed functionally graded coatings based on a polyimide matrix filled with varying volume fractions of WC–Co have been investigated to improve the erosion and oxidation resistance of polymer matrix composites. A study of the coatings' effectiveness as erosion barriers was accomplished through a statistical analysis of the results of solid particle erosion testing of coated and uncoated polymer matrix composite (PMC) samples using a design of experiments (DoE) approach. Two coating systems and a control sample were evaluated in a randomized test matrix. The coatings were tested at room temperature and 250 °C, using an alumina erodent impacting the coatings at a speed of 100 m/s at angles of 20° and 90°. In general, as the angle of incidence of the eroding material increased from 20° to 90° the volume loss increased. Erosion volume loss at 250 °C was approximately twice that at room temperature.

Solid particle erosion of thermal sprayed coatings

Thermal sprayed coatings are commonly employed to enhance the wear resistance of a wide range of engineering components. Coatings of tungsten carbide based hardmetal, nickel based self-fluxing alloy and composites on the basis of NiCrSiB alloy were deposited from these powder by the detonation gun, continuous detonation spraying, and spray fusion process. Solid particle erosion tests were performed on these coatings with silica abrasives of size in between 0.1 and 0.3 mm. Influence of the test variables and material parameters is discussed. Differences in the wear behavior are rationalized in terms of the coating hardness and structure. Case study of the wear resistance of the coatings in disintegrator mill is proposed.

Erosion resistance performance of magnetron sputtering deposited TiAlN coatings

TiAlN coatings with different Al concentrations have been deposited on Ti–6Al–4V substrate by reactive magnetron sputtering and characterized by scanning electron microscopy, nanoindentation and solid-particle erosion testing. It has been found that erosion resistance of TiAlN coatings depends not only on the coating chemistry, but also on the deposition conditions (microstructures). TiAlN coatings demonstrate marked improvement in erosion performance with the best erosion resistance several times higher than TiN coating. The excellent erosion resistance results from a good combination of high hardness and good toughness.

Effects of Eutectic Carbide Content on Erosion Behaviors in Ductile Cast Irons

During the casting process of thin-wall parts, due to fast cooling rate or chemical composition of the ductile iron, iron carbide (cementite) may exist in the microstructure that retards the mechanical properties of the iron greatly. In this study we discuss the effects of eutectic carbide contents in relation to the cooling parameters and the erosion behavior of the erosion incident angle on the casting specimens. Different content of eutectic carbide was produced by varying the cooling rate and silicon content. Solid particle erosion tests were performed using a shot-blasting machine with angular Al2O3 particles. The results show that, the largest amount of eutectic carbon (plate-like) exists in the faster cooling rate and lower silicon content. The amount of pearlite and nodules counts produced at lower cooling rates also decreased accordingly. Erosion rate also was found in the same trend that higher carbide content yielded better erosion resistance and lower erosion rates, but the amount of reduction is lower than the amount of increase on the hardness level. The maximum erosion rate occurred at the incident angle equaling to π/4.5, and the deepest erosion penetration occurred at an incident angle of π/3.6 for four comparison specimens. The impinged surface morphologies of four specimens exhibit cutting and plowed furrows at lower incident angles, but the overlapped chippings at higher incident angles. The erosion mechanisms, at medium and high incident angle erosion, show fatigue crack and subsurface lateral crack propagation in higher eutectic carbide specimen, but platelet peeling-off and internal crack and deformation in lower eutectic carbide specimen. The test also revealed that the failure mechanism of the casting thin plates tend to be ductile-brittle fracture.

The tribological performance of ultra-hard ceramic composite coatings obtained through microarc oxidation

A dense ceramic oxide coating approximately 100 μm thick was prepared on a 7075 Al alloy by microarc oxidation in an alkali-silicate electrolytic solution. Coating thickness and surface roughness (Ra) were measured during coating formation. The influence of current density, electrolyte temperature and inter-electrode distance on coating kinetics was investigated. Microstructure and phase compositions were analysed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The microhardness of the coating was also measured. The tribological performance of the coatings was evaluated using a dry sand abrasion test, a solid particle erosion test and a pin-on-disc sliding wear test. In addition, the results are compared to detonation-sprayed alumina (Al2O3) coating and bulk Al2O3. The basic mechanism of microarc coating formation is explained. The material removal mechanism during solid particle erosion was investigated, and structure–property correlations were established.

Wear of iron–aluminide intermetallic-based alloys and composites by hard particles

In this study, the resistance of alloys and composites based on the intermetallic compounds Fe 3Al and FeAl to wear by hard particles was assessed and compared to the behavior of selected metals, alloys, other intermetallic compounds and ceramics. Pin abrasion tests were performed on these materials at room temperature. Among other things, it was found that as the Al atomic percent in binary Fe–Al increased, the alloys became more abrasion resistant. In summary, the ranking of the alloys in terms of abrasion resistance from the most resistant to the least resistant proceeds as follows: FeAl>Fe 3Al>α-Fe alloy with 16 at.% Al>pure Fe>pure Al. These results are discussed in terms of the hardnesses of the respective alloys. The addition between 40 and 70 vol.% of a hard second phase (e.g. TiC or TiB 2) decreased the wear rate of the Fe 3Al and FeAl composites by an order of magnitude compared to the parent alloy. In addition, solid particle erosion tests were performed on an FeAl alloy, and FeAl+80 vol.% TiC, FeAl+80 vol.% WC, FeAl+80 vol.% TiB 2 cermets at 25, 180, 500 and 700°C, and the results were compared to erosion behavior of several conventional alloys and cemented carbides (WC–Co). The ranking of the erosion resistance of the FeAl alloys and composite materials was as follows: (most resistant) FeAl–WC>FeAl–TiB 2>FeAl–TiC>FeAl (least resistant). This behavior was related to both the cermet microstructure and material removal mechanisms.

Mechanical properties and features of erosion of cermets

The erosive wear resistance of cermets with different composition, structure and properties has been investigated. It has been shown that cermets erosive wear resistance cannot be estimated only by hardness, characterised by resistance to penetration. The differences in wear resistance between cermet materials with equal hardness level can be attributed to differences in their resistance to fracture. The present paper discusses some features of the material removal process during the particle–wall collision. Solid particle erosion tests on eight materials have been performed using silicon carbide and silica abrasive particles within a range of erodent size of 0.1–0.3mm, impact angles from 30 to 90° and particle velocity from 30 to 80ms−1. In order to clarify the details of the impact, the process of interaction of solid particles with cermet targets was studied using a laser Doppler anemometer (LDA) measuring technique. Systematic studies of the influence of the impact variables on the collision process have been carried out.