Particle Erosion Tests Research Articles

Erosion Behavior of CA-15 Tempered Martensitic Stainless Steel

Martensite stainless steel (MSS) possesses excellent strength and medium corrosion resistance, and is often used in industrial applications, such as for highly stressed parts like turbine blades and pipe materials. However parts are often damaged by flow field particles interact with the materials, in a solid particle erosion (SPE) phenomenon, which may even lead to injuries. In this paper we discuss the effects of the tempering treatment and the erosion incident angle on the CA-15 MSS erosion behavior. The results show that, in single particle erosion tests, the main mechanisms that cause problems are micro-cutting and deformation craters at low and high incident angles, respectively. In repetitive particle erosion tests, grain boundary cracking is one of the main fracture mechanisms. The platelet mechanism also obvious affected at high incident angle erosion. Materials tempered at 573–673 K, tempered martensitic embrittlement (TME) occurred, which caused serious boundary cracking and grain broken-down. The serious erosion damage showed at medium incident angle for this material that result in combine of cutting, deformation crater, and cracking mechanism. The maximum erosion rate of material occurred at an incident angle of �= 6 and the deepest erosion penetration occurred at an incident angle of �= 4.

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.

Protection of industrial sensors with ta-C

Tetrahedral amorphous carbon (ta-C) coatings are a very promising approach in order to develop chemically and mechanically resistant protective layers for industrial and medical applications. For this purpose our group has developed thick (50–200 μm), high-quality (sp 3-fraction ∼80%) and hydrogen-free protective ta-C coatings deposited (5 μm/h/20 cm 2) with filtered pulsed arc discharge (FPAD) method. Earlier ta-C coatings have given excellent results in aluminium lathing. For this work ta-C films were tested on paper thickness, density and porosity probes, paper paste viscometer nozzles and support pieces of a water-jet cutter. Tests were performed both in laboratory and industrial environments. In the paper mill the paper sensors and the cutter support pieces were in constant contact with the high-speed (up to 100 km/h) travelling paper web. The ta-C coating reduced significantly the erosion of the sensors and the resin accumulation on the sensor contact surfaces. The viscometer nozzle pieces were tested under pressures that no other material has withstood. In particle erosion tests ta-C coating outperformed WC-Co hard metal, sintered SiC, sintered Al 2O 3, synthetic ruby and TiN coatings (Diamond Rel. Mater. 9 (2000) 1524).

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.

An evaluation of plasma sprayed ceramic coatings by erosion, abrasion and bend testing

The mechanical properties of a series of plasma sprayed ceramic coatings made from alumina, chromia and alumina–titania precursor powders have been evaluated in particle erosion, two-body abrasion and bend testing. For the alumina coatings, both monocrystalline (sapphire) and polycrystalline alumina powders of varied grit sizes were used. Also, coatings of chromia and a mixture of alumina and titania were evaluated. The coatings were deposited with an axial injection spraying technique. Clear differences were found between the investigated coatings. Among the alumina coatings, those deposited from sapphire powders gave the best results in the wear tests. An addition of titania to alumina had a favourable effect in most tests. In abrasion, one chromia coating displayed a wear resistance comparable to the dense sintered alumina reference. The erosion rates were, however, several times higher for all sprayed coatings compared to the reference alumina.

A study on SiO 2 particle erosion of flake graphite and spheroidal graphite cast irons

Types A and D flake graphite cast irons (Fe 3.11 wt.%–C 1.85 wt.%–Si) and spheroidal graphite cast irons of two different nodule distributions (Fe 3.54 wt.%–C 2.48 wt.%–Si), each with ferritic and martensitic matrices, were chosen in conduct SiO 2 particle erosion tests in this study (average particle velocity ∼66 m s −1). For the cast irons of the same matrix phase, the results indicated that spheroidal graphite of coarser distribution led to better erosion resistance than finer distribution. Type A flaky graphite led to better erosion resistance than type D and, on the whole, spheroidal graphite led to better erosion resistance than flaky graphite. For those with the same graphite morphology and distribution, ferritic matrix results in less wear loss when eroded under large-angle impact; martensitic matrix results in less wear loss under oblique impact. Brittleness effect of both martensitic matrix and flaky graphite will cause maximum erosion rate to occur at higher impact angles.

Improvements of the microstructure and erosion resistance of boron carbide with additives

A series of test materials were produced from boron carbide (B4C) powders with additions of either boron in amounts up to 60 wt.%, silicon (4 wt.%) or silicon and silicon carbide (4 wt.% and 30 wt.%, respectively). The powder mixtures were densified by encapsulation hot-isostatic pressing. The test materials where evaluated in dry particle erosion tests with silicon carbide grits. Particular attention was given to the relation between the microstructure and the composition.It was found that boron additions up to 20 wt.%, decreased the average grain size and reduced the porosity of the boron carbide. A material with 60 wt.% boron exhibited very low porosity and supreme resistance to particle erosion. The erosion resistance was also significantly improved by additions of silicon and silicon carbide.The favorable effects of boron, silicon and silicon carbide are discussed in terms of their influence on microstructural parameters, such as grain size, porosity, grain boundaries and reduction of free carbon.

The erosion of four materials using seven erodents — towards an understanding

In order that an overview of the erosion process be obtained, solid particle erosion tests on four materials have been performed using seven different erodents within a range of particle diameters D (63 to 1000 μm), velocities V (33 m s −1 to 99 m s −1) and impact angles α (30° to 90°). The materials are glass, alumina, WC–7% Co and 304 stainless steel. Seven erodents are steel shot, glass beads, silica, alumina, tungsten carbide, silicon carbide and diamond particles. Systematic studies of the influence of the impact variables on the erosion rate have been made. Scanning electron microscopy of the eroded surface and the erodents after impact has been performed. Empirical correlations between erosion rate and the parameters of erodents are obtained and discussed in terms of the modes and mechanisms of erosion. An analysis of these results reveals that for brittle materials, glass and alumina, the erosion rate is determined by kinetic energy, particle size and the relative hardness and toughness of erodents. However, for ductile materials, the shape and kinetic energy of erodents are the most important factors determining the erosion rate. There is no significant effect of hardness and toughness of erodents on erosion. An attempt to rationalise the results in terms of mechanisms has been made.

A Comparative Study of Tribological Behavior of Plasma and D-Gun Sprayed Coatings under Different Wear Modes

In recent years, thermal sprayed protective coatings have gained widespread acceptance for a variety of industrial applications. A vast majority of these applications involve the use of thermal sprayed coatings to combat wear. While plasma spraying is the most versatile variant of all the thermal spray processes, the detonation gun (D-gun) coatings have been a novelty until recently because of their proprietary nature. The present study is aimed at comparing the tribological behavior of coatings deposited using the two above techniques by focusing on some popular coating materials that are widely adopted for wear resistant applications, namely, WC-12% Co, A12O3, and Cr3C2-MCr. To enable a comprehensive comparison of the above indicated thermal spray techniques as well as coating materials, the deposited coatings were extensively characterized employing microstructural evaluation, microhardness measurements, and XRD analysis for phase constitution. The behavior of these coatings under different wear modes was also evaluated by determining their tribological performance when subjected to solid particle erosion tests, rubber wheel sand abrasion tests, and pin-on-disk sliding wear tests. The results from the above tests are discussed here. It is evident that the D-gun sprayed coatings consistently exhibit denser microstructures and higher hardness values than their plasma sprayed counterparts. The D-gun coatings are also found to unfailingly exhibit superior tribological performance superior to the corresponding plasma sprayed coatings in all wear tests. Among all the coating materials studied, D-gun sprayed WC-12%Co, in general, yields the best performance under different modes of wear, whereas plasma sprayed Al2O3 shows least wear resistance to every wear mode.

Erosion Testing of Coatings for Aero Engine Compressor Components

The results from a comparative study of erosion resistance of various coatings and some material modification treatments for protecting compressor airfoils made of 17-4 PH stainless steel against sand erosion, are presented. Coatings based on either aluminum, nickel or titanium nitride and material modifications by ion implantation and cryogenic treatment were evaluated by dry particle erosion testing in accordance with the ASTM G76-83 Standard Practice, at different angles of impingement (30°, 60° and 90°). The TiN coatings applied by PVD techniques, were found to be the most erosion resistant. All the PVD deposition techniques appeared capable of producing durable coatings, but in degrees that varied with the deposition method and vendor. All the TiN coatings investigated proved more resistant to erosion at a 30° impingement angle. The implications for compressor airfoil applications are discussed.

The solid particle and cavitation erosion of titanium aluminide intermetallic alloys

The mode of material removal during solid particle erosion and cavitation erosion of rolled super α 2 and plasma arc-melted γ titanium aluminide alloys have been investigated. These low density, high strength materials have potential application in turbine engine components, where the service conditions are potentially erosive, and there is a consequent interest in the erosion behaviour. Particle erosion tests were performed using an air blast rig, and vibratory equipment with a stationary specimen were used to investigate the cavitation erosion performance. Erosion rates were measured and characteristic damage features were identified on the surface of eroded specimens. The mechanisms of erosion are discussed in order to explain the promising performance of the materials in erosive conditions.

Properties of alumina-based coatings deposited by plasma spray and detonation gun spray processes

Alumina, Al2O3 + 3 to 40 wt% TiO2, and Al2O3 + 40 wt% ZrO2 coatings were deposited by atmospheric plasma spraying (APS) and detonation gun spraying (DGS). The coatings were evaluated by optical microscopy, microhardness measurements, and X- ray diffraction. Wear resistance of the coatings was evaluated by rubber wheel sand abrasion and particle erosion test methods. Detonation gun- sprayed coatings exhibited more homogeneous microstructures and somewhat higher microhardness than corresponding plasma- sprayed coatings. Small additions of TiO2 (3 wt%) improved both the abrasion and erosion wear resistance, whereas 40 wt% TiO2 significantly decreased the erosion wear resistance of both APS and DGS coatings. Alumina + 40% ZrO2 coatings exhibited the best abrasion wear resistance of both APS and DGS coatings, but the erosion wear resistance of these coatings was lower than that of the Al2O3 and Al2O3 + 3 wt% TiO2 coatings. The best abrasion wear resistance of the coatings studied was obtained with DGS Al2O3 + 40 wt% ZrO2 and Al2O3 + 3 to 40 wt% TiCh coatings. These coatings exhibited lower wear rates than bulk Al2O3. The best erosion wear resistance was obtained with the DGS Al2O3 + 3 wt% TiO2 coating; however, it exhibited a higher wear rate than bulk Al2O3. In general, detonation gun- sprayed coatings showed significantly enhanced abrasion and erosion wear resistance than the corresponding plasma- sprayed coatings.

Wear and erosion behavior of plasma-sprayed WC-Co coatings

Wear mechanisms of air plasma-sprayed WC-12%Co coatings were studied by using a dry sand rubber wheel (DSRW) abrasive, ring-on-square adhesive wear, and alumina particle erosion tests. Coating properties such as intersplat cohesive strength, porosity, surface roughness, hardness, and retained carbide as well as microstructures were characterized to assess their relationship on wear performance. Porosity, hardness, surface roughness, and retained carbide of the coatings are not the principal factors affecting wear performance. Intersplat cohesive strength of coatings, measured by a simple bonding test, is the most significant factor that relates to the wear rate of thermal spray coatings.

On the wear of aluminium and magnesium metal matrix composites

The effect of fibre reinforcement of aluminium, magnesium and Mg-9Al-1Zn on the wear properties has been investigated. Dry sliding, two- and three-body abrasion and solid particle erosion testing were performed. The results show that the tribological behaviour of metal matrix composites (MMCs) depends very much on the type of MMC and the type of contact situation, i.e. tribosystem. The dominant wear mechanisms are identified by light optical microscopy, scanning electron microscopy and energy dispersive X-ray spectroscopy. In dry sliding an optimum wear resistance was obtained at a fibre content of approximately 10%. Magnesium and the magnesium alloy showed an increasing two-body abrasion resistance with increasing fibre content while no positive effects were observed in three-body abrasion. The abrasion rate of aluminium was not affected by the fibre content. In erosion, aluminium and magnesium displayed decreasing wear resistance with higher fibre content whereas the magnesium alloy was hardly affected. The relations between wear rate, wear mechanisms and matrix parameters are discussed.

Erosion resistance of diamond coatings

Preliminary solid particle erosion testing of 10 μm thick diamond films on silicon substrates showed excellent erosion resistance. The application of diamond coatings to materials that are commonly used in erosive environments should result in significant improvement over other erosion-resistant coatings. Diamond films were applied to silicon, tungsten and Ti-6Al-4V using a high-pressure microwave-assisted plasma deposition system and were determined to have a high degree of sp3 bonding using Raman spectroscopy.Erosion tests were performed on diamond-coated silicon, tungsten and Ti-6Al-4V, as well as on uncoated substrates and alternative coatings. The erosion resistances of the target materials were compared using volume loss versus erodent mass plots and steady-state erosion-rate data. Diamond-coated silicon showed the highest erosion resistance. Diamond-coated Ti-6Al-4V also showed high erosion resistance when compared with uncoated materials.Erosion mechanisms were identified by examination of eroded surfaces using scanning electron microscopy. Diamond coatings on Ti-6Al-4V substrates fail by delamination of the coating from the substrate. This is believed to be a result of high residual stresses and stress concentrations at the coating-substrate interface. Diamond coatings on silicon and tungsten substrates are gradually removed by a brittle erosion process.

Effects of erodent recycling in solid particle erosion testing

In solid particle erosion tests, recycling of the erodent can lead to rounding, or in some cases significant fracture, of the particles, and thus to a progressive change in the test conditions. This work examines changes in particle size and shape resulting from impact, for a typical silica sand and for glass spheres. The target material was a glass-ceramic, and experiments were performed with an air-blast erosion rig. Erodent particles classified by sieving contained a significant proportion outside the nominal size range. Particle size distributions determined by sieving and optical methods showed disparities, due to particle shape effects. Both types of particles showed extensive fragmentation on striking glass-ceramic targets at 89–98 m s −1 at normal incidence. Repeated impact led to further fragmentation and a progressive reduction in the average particle size in the erodent sample, although some particles remained unbroken after more than ten impacts. The fragmentation of the particles led to changes in the measured erosion rate as they were recycled. At least three factors were responsible: the intrinsic size effect, aerodynamic effects in the gas-blast erosion rig, and changes in particle angularity due to fracture.

Solid Particle Erosion of Fiber Reinforced Plastics

Solid particle erosion tests were carried out to study the effect of matrix materials, reinforcement fibers, interface strength between matrix material and fibers, im pact angle, and particle velocity on the solid particle erosion behavior of fiber reinforced plastics. In the present study, special attention was focused on the effect of the interface strength between matrix material and fibers, which has not been investigated in a lot of previous works related with the erosion of composite materials. FRPs with treated or un treated fiber surfaces were used as test materials to study the effect of interface strength be tween matrix material and fibers. It is found from the erosion tests that the erosion rate is larger in a FRP than in a neat resin, and that the erosion rate of a FRP decreases with the increase of the interface strength between matrix material and fibers.

Improved Langmuir probe surface coatings for the Cassini satellite

A Langmuir probe will be used on the space research satellite Cassini in order to monitor electron density fluctuations in space plasmas surrounding Saturn. In order to obtain well-defined Langmuir probe characteristics a surface with uniform work function Φ must be used. A graphite coating has been used on earlier earth-bound satellite probes, but for the Cassini satellite to Saturn a hard, wear-resistant coating must be used. In this contribution we report on investigations of titanium nitride (TiN) coatings for this purpose. TiN coatings have been prepared by high temperature nitriding in pure nitrogen gas and by reactive magnetron sputtering on plane titanium and titanium alloy substrates. The resulting coatings have been analysed with laterally resolved, relative Φ measurements, and the tribological properties of the coatings have been investigated by solid particle erosion and scratch testing. In the tests, the graphite coating DAG 213 used on earlier satellite probes was used as a reference material. The results show that the TiN coatings are superior to the graphite coating with regard to both photoelectric properties and solid particle impact resistance. The sputtered coatings exhibit the lowest lateral work function variation, but the nitrided coatings have superior erosion resistance. The results demonstrate that TiN coatings are suitable for space plasma probes.

How TiN coatings improve the performance of high speed steel cutting tools

TiN coatings deposited onto high speed steel (HSS) by physical vapour deposition have successfully been used in metal cutting applications for a number of years. Many papers have been presented which all show that TiN coatings often yield decreased wear rates and, usually, reduced friction coefficients. Although different theories are proposed in the literature (hardness theory, diffusion barrier theory, thermal barrier theory, reduced friction theory etc.), most papers have not dealt with the question of how and why TiN coatings modify the performance of HSS cutting tools. The present paper contributes to the answer of this question by (1) organizing published information about significant mechanical and chemical properties of TiN and (2) closely discussing different proposed theories and making comparisons with results from the broad spectrum of experiments (tool wear simulation testing, scratch testing in a scanning electron microscope, particle erosion testing, chip formation studies, metal cutting etc.) performed by the authors. A unique combination of sufficient adhesion to the substrate, high hot hardness, high wear resistance and an ability to improve the contact conditions at the cutting edge is concluded to be the answer. The complex interrelationships encompassed by this explanation are displayed in a flowchart. The thermal barrier function and the relatively low sliding friction coefficient of TiN are believed to be of minor importance.