Erosion wear testing evaluates the resistance of metals, ceramics, polymers and protective coatings to material loss caused by solid particle impingement, slurry flow, liquid droplet impact and cavitation. Performed in accordance with internationally recognized standards such as ASTM G76, ASTM G32 and ASTM G73, these tests quantify erosion rates, reveal dominant wear mechanisms and support material selection and coating qualification. Accredited third-party laboratories provide reproducible, traceable data that helps manufacturers extend component service life in aggressive erosive environments.
Technical Overview
Erosion wear is the progressive loss of material from a solid surface caused by the mechanical action of impacting particles, liquid droplets, or collapsing vapor bubbles carried in a moving fluid. Unlike abrasive wear, which arises from sliding contact between solid surfaces, erosion is governed by kinetic energy transfer at the instant of impact. It is a leading degradation mechanism in turbomachinery, pipelines, pumps, valves, and many other systems that handle aggressive media such as sand-laden gas streams, slurries, or high-velocity droplet fields.
The severity of erosion depends on a complex interaction of variables, including particle velocity and impact angle, erodent particle size, shape and hardness, particle flux, target material properties, and environmental factors such as temperature and corrosivity. Because field conditions are difficult to reproduce and in-service component trials are slow and costly, standardized laboratory erosion testing provides a controlled, accelerated and reproducible basis for ranking materials, verifying surface protection systems and validating design predictions.
Principal Erosion Mechanisms
- Micro-cutting and ploughing by sharp particles striking at oblique angles
- Repeated plastic deformation, platelet formation and fatigue-driven detachment at near-normal incidence
- Brittle cracking, radial fracture and spallation in ceramics, glasses and some hard coatings
- Cavitation erosion caused by the implosion of vapor bubbles adjacent to the surface
- Erosion–corrosion synergism in electrically conductive liquid media
Governing Parameters
- Impact velocity: erosion rate typically follows a power law, where the exponent ranges from approximately 2 to 3.5
- Impact angle: ductile metals exhibit maximum erosion near 15–30 degrees, while brittle materials peak near 90 degrees
- Erodent characteristics: particle size distribution, angularity, and hardness relative to the target
- Exposure time: an incubation stage with little measurable loss precedes the steady-state erosion regime
Testing Samples
Metallic Materials
Carbon and low-alloy steels, stainless steels, cast irons, aluminum and titanium alloys, nickel-based superalloys, and copper alloys in the form of machined flat coupons with defined surface finish and heat-treatment condition.
Ceramics, Cermets and Hardmetals
Alumina, zirconia, silicon carbide and silicon nitride ceramics, tungsten carbide–cobalt hardmetals and titanium-based cermets used for nozzles, seals, cutting edges and wear pads.
Polymers, Elastomers and Composites
Polyethylene, UHMWPE, polyamide, PTFE, polyurethane and rubber linings, epoxy-based protective systems, and fiber-reinforced polymer composites such as wind turbine blade skins.
Coatings and Surface Engineered Layers
Thermal spray coatings produced by HVOF, plasma and arc processes, PVD and CVD hard coatings, weld overlays and hardfacings, anodized and conversion layers, and organic anti-erosion paints, tested on standardized substrates.
Actual Components
Where geometry permits, real components such as pump impellers, turbine blades, pipe spools and bends, choke valves and spray nozzles can be assessed directly or through specimens sectioned from service-exposed parts.
Testing Items
- Mass loss and volume loss of specimens after defined exposure intervals
- Erosion rate normalized to erodent mass consumed, expressed in mm³/g or mg/g, or normalized to exposure time
- Incubation period determination and steady-state erosion rate
- Erosion-versus-impact-angle mapping at 15, 30, 45, 60 and 90 degrees
- Velocity exponent determination for life prediction models
- Erodent characterization: particle size distribution, hardness and shape factor
- Surface roughness and three-dimensional topography before and after testing
- Microhardness profiles and cross-sectional thickness loss of eroded zones
- Wear mechanism identification by optical microscopy, SEM and EDS analysis
- Erosion–corrosion synergy evaluation in electrolytes with electrochemical monitoring
Testing Methods
Solid Particle Erosion Testing (ASTM G76)
The most widely applied method for dry particle erosion. Compressed gas accelerates a metered stream of erodent, typically alumina with a nominal particle size of about 50 µm, through a calibrated nozzle toward the specimen surface. Controlled variables include particle velocity, commonly between 30 and 150 m/s, particle feed rate, nozzle standoff distance, impact angle and exposure time. Specimens are weighed before and after each interval, and the normalized erosion rate is calculated from volume loss divided by the mass of erodent delivered.
Slurry Erosion Testing
Slurry pot testers and recirculating loop or jet rigs expose rotating or stationary specimens to sand-laden liquids under controlled velocity, solids concentration, particle size, temperature and chemistry. This approach reproduces the erosive conditions found in dredging, mining and oilfield transport, and enables simultaneous evaluation of combined erosion–corrosion behavior when the medium is corrosive.
Cavitation Erosion Testing (ASTM G32 and ASTM G134)
ASTM G32 employs a vibratory apparatus operating at approximately 20 kHz to generate intense cavitation in a liquid bath, either with the specimen attached to the horn or held stationary at a defined gap. ASTM G134 uses a submerged cavitating jet to produce bubble collapse on the specimen surface. Both methods determine mass loss curves, incubation times and maximum erosion rates for materials exposed to cavitating liquids.
Liquid Impingement Erosion Testing (ASTM G73)
Specimens mounted on a rotating arm repeatedly pass through liquid jets or droplet fields, simulating rain erosion of aircraft radomes, cockpit transparencies, wind turbine leading edges and steam turbine last-stage blades. Exposure is quantified by the volume or mass of liquid impinged per unit area, and results are expressed as erosion rate versus cumulative exposure.
Specimen Preparation and Data Evaluation
Specimens are prepared to a defined surface finish, typically ground or polished, then degreased, ultrasonically cleaned, dried and weighed to 0.1 mg on a calibrated analytical balance. Each condition is tested with a minimum of three replicates. Cumulative mass loss is plotted against exposure time or erodent mass to identify the incubation period and steady-state erosion rate. The final report documents material and erodent data, test parameters, normalized erosion rates, scatter analysis and post-test morphology images.
Applications
Aerospace and Gas Turbines
Qualification of compressor blade and turbine materials resistant to sand and dust ingestion, rain erosion assessment of transparencies and radomes, and ranking of protective coatings for hot-section and fan components.
Oil, Gas and Petrochemical
Erosion screening of pipeline steels, elbows, tees, chokes and valves exposed to sand production, evaluation of hardfacings and ceramic linings for downhole tools, and verification of integrity-management models.
Power Generation
Material selection for steam turbine last-stage blades, boiler tube and economizer protection from fly ash, wear-life studies of coal pulverizer and ash-handling components, and FGD system slurry equipment.
Mining, Dredging and Slurry Transport
Comparative testing of white irons, elastomer linings, ceramics and hardmetal grades for slurry pumps, hydrocyclones, pipes and chute liners handling abrasive suspensions.
Wind Energy and General Industry
Leading-edge erosion evaluation of blade coatings and erosion shields, durability ranking of protective paints for infrastructure exposed to airborne dust, and incoming-material quality control for critical wear parts.
FAQ
What is the difference between erosion wear and abrasive wear?
Erosion is caused by particles, droplets or cavitation events striking a surface at velocity, whereas abrasion results from particles or asperities under sliding or rolling contact between solid surfaces. The distinction matters because the dominant material-removal mechanisms and the best-performing materials differ significantly between the two.
Which standards govern erosion wear testing?
ASTM G76 covers solid particle erosion by gas jet impingement, ASTM G32 and ASTM G134 cover cavitation erosion, ASTM G73 covers liquid impingement erosion, ASTM G119 addresses wear–corrosion synergism, and ASTM G40 defines the standard terminology for wear and erosion.
How are erosion test results expressed?
Results are typically reported as volume loss or mass loss, normalized erosion rate in mm³ of material removed per gram of erodent, incubation time, and steady-state erosion rate. Supporting data include impact-angle dependence curves, velocity exponents and post-test surface morphology.
What specimen size and quantity are required?
Common specimen formats are flat coupons of approximately 25 mm × 25 mm or 25 mm diameter discs with a thickness of 3 to 6 mm and a ground or polished finish. At least three replicates per test condition are recommended to manage data scatter, and material composition, hardness and heat-treatment condition should be documented.
Why do ductile and brittle materials respond differently to impact angle?
Ductile metals lose material mainly through cutting and deformation fatigue, so erosion peaks at shallow impact angles of roughly 15 to 30 degrees. Brittle ceramics and glasses fail by crack initiation and spallation, so erosion is most severe at normal incidence near 90 degrees. Mapping this behavior is essential for equipment operating at mixed impact angles.
Can erosion be evaluated together with corrosion?
Yes. Slurry erosion tests can be conducted in corrosive electrolytes with electrochemical techniques such as polarization resistance monitoring during exposure. Following the ASTM G119 framework, the total material loss can be separated into pure erosion, pure corrosion and the synergistic interaction, which often dominates in conductive media.