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ISO 28080:2021 — Hardmetals — Abrasion Tests for Hardmetals
Technical Article
1. Overview of ISO 28080:2021
ISO 28080:2021 specifies a generic test method to determine the abrasion wear characteristics of hardmetals, which are composite materials of hard carbide particles (typically tungsten carbide, WC) bound in a metallic matrix (usually cobalt, Co). This standard provides a comprehensive framework for rotating-wheel abrasion testing, bringing together key features from established ASTM methods including ASTM G65 (dry sand/rubber wheel), ASTM B611 (steel wheel/high stress), and ASTM G105 (wet sand/rubber wheel). The standard was developed by ISO/TC 119 Powder metallurgy, Subcommittee SC 4 Sampling and testing methods for hardmetals, in collaboration with CEN.
The rotating-wheel abrasion test is one of the most widely used methods for evaluating wear resistance of WC/Co hardmetals in demanding industrial applications such as mining, drilling, materials handling, and mineral processing. Hardmetals are selected precisely because of their exceptional wear resistance, and standardized testing enables engineers to compare materials, predict service life, and optimize compositions for specific operating conditions. This second edition technically revises the 2011 version with updated normative references, reorganized clauses, and the addition of neoprene as an acceptable wheel rim material.
The rotating-wheel abrasion test is one of the most widely used methods for evaluating wear resistance of tungsten carbide/cobalt (WC/Co) hardmetals in industrial applications such as mining, drilling, and materials handling.
2. Test Principle, Variants, and Key Apparatus Components
The fundamental principle involves a rotating wheel pressed against a test piece with abrasive material introduced at the contact interface. Two primary test system variants exist: Variant 1 features a horizontal test piece pressed into the top of the wheel, while Variant 2 holds the test piece vertically against the wheel edge. The ASTM G65 and B611 methods are examples of Variant 2 configurations. The wheel may be solid steel AISI 1020 grade for high-stress tests (per ASTM B611) or have a chlorobutyl rubber or neoprene rim for low-stress tests (per ASTM G65 or G105), with Shore A Durometer hardness as specified in those standards.
| Parameter | Typical Condition | Notes |
|---|---|---|
| Test load | 130 N | Dead-weight loading via lever arm system |
| Wheel peripheral speed | 1 m/s | Motor must be powerful enough for stable constant speed |
| Abrasive flow rate through contact | 150 g/min | Critical parameter requiring careful calibration |
| Test duration | 20 min | Can be single-step or multiple interrupted steps |
| Wheel diameter (ASTM G65) | 228.6 mm | Rubber rim thickness 12.7 mm |
| Wheel diameter (ASTM B611) | 169 mm maximum | Steel wheel, replace when diameter reduces by 4 mm |
| Test piece size | 40-70 mm x 20-25 mm | Thickness not critical if sufficiently robust |
The apparatus includes an abrasive-feed mechanism (vibrating feed, screw auger, or slotted rotating disc), a vacuum extraction system for dry tests to collect potentially hazardous fine debris, and optional instrumentation for measuring friction force via load cell, normal force via lever-arm load cell, and depth of wear via displacement transducer. The abrasive flow must be carefully measured, with baffles to divert any abrasive that does not pass through the wearing contact.
The results of abrasion tests depend critically on the shape, size, and size distribution of the abrasive. For comparable results, the same abrasive should be used across tests, ideally sourced from the same supplier with consistent quality control.
3. Test Procedure, Specimen Preparation, and Expression of Results
Test pieces are cleaned ultrasonically in acetone for 10 minutes before testing. Mass is measured to 0.1 mg precision, and density is determined per ISO 3369. Surface finish significantly affects initial wear rates: a weakened surface from preparation can increase initial wear, while residual compressive stress may reduce it. As these surface regions are worn away, the wear rate approaches the normal bulk material value.
The test can be conducted as a single long-duration step or as interrupted multiple steps with reweighing between steps, which is useful for detecting transitions in wear behaviour due to surface damage. However, interrupted tests can give different results from continuous tests due to surface disturbance during cleaning and repositioning. At least two repeat tests shall be carried out for each material. The abrasion volume loss V is calculated from mass loss M and density rho using V = M/rho. For multi-step tests, regression analysis on the linear portion of the data determines the abrasion rate, using only data points from the linear region.
Engineering Design Insights
For engineers designing hardmetal components for abrasive service, understanding the relationship between microstructure (carbide grain size, binder content) and wear resistance is critical. WC/Co hardmetals with higher hardness (HV30) generally exhibit lower volume loss, though the relationship depends on the abrasive material used. Alumina abrasive produces more aggressive wear than silica sand, making it suitable for simulating high-stress abrasion conditions. The choice between steel and rubber wheels enables simulation of different contact mechanics: steel wheels for high-stress abrasion where abrasive particles are crushed, and rubber wheels for low-stress three-body abrasion where particles roll between compliant rim and test piece. Interlaboratory comparisons of ASTM B611 tests showed that the average difference between two results for each material was only 5 percent, demonstrating that good repeatability is achievable when a well-defined test procedure is rigorously followed.
Interlaboratory comparisons of ASTM B611 tests showed that the average difference between two results for each material was only 5%, demonstrating good repeatability when a well-defined procedure is followed.
4. FAQs
Q: What is the difference between the steel wheel and rubber wheel tests?
A: The steel wheel test (ASTM B611) simulates high-stress abrasion where abrasive particles are crushed between wheel and test piece. The rubber wheel test (ASTM G65/G105) simulates low-stress three-body abrasion where abrasive rolls between the compliant rubber rim and the test piece, more representative of sliding wear in materials handling.
A: The steel wheel test (ASTM B611) simulates high-stress abrasion where abrasive particles are crushed between wheel and test piece. The rubber wheel test (ASTM G65/G105) simulates low-stress three-body abrasion where abrasive rolls between the compliant rubber rim and the test piece, more representative of sliding wear in materials handling.
Q: Why is abrasive moisture content important?
A: Moisture content should be less than 1% by mass. Wet abrasive can clog the feed system and alter the abrasion mechanism, leading to non-repeatable results. Moisture is measured by weighing, heating to 105 C for one hour, and reweighing.
A: Moisture content should be less than 1% by mass. Wet abrasive can clog the feed system and alter the abrasion mechanism, leading to non-repeatable results. Moisture is measured by weighing, heating to 105 C for one hour, and reweighing.
Q: How many repeat tests are required and why?
A: At least two repeat tests under identical conditions for each material, to assess test variability and ensure statistical confidence in the reported abrasion rate.
A: At least two repeat tests under identical conditions for each material, to assess test variability and ensure statistical confidence in the reported abrasion rate.
Q: What should the test report include?
A: Full documentation including test system type, abrasive material and size, flow rate, test duration, wheel speed, volume loss, abrasion rate, and any anomalies such as non-linear behaviour or incubation time.
A: Full documentation including test system type, abrasive material and size, flow rate, test duration, wheel speed, volume loss, abrasion rate, and any anomalies such as non-linear behaviour or incubation time.
