Exceed Consulting – wear testing unit
12 June 2017
Visit to Exceed Consulting – wear testing unit
Jeff Dunning and Adam Dunning
L to R: Jeff Dunning, Louise Petrick (Perth Branch President)
Jeff Dunning established Exceed Consulting in 2003. It provides a wide range of metallurgical and materials analysis, testing and inspection services. While the range of services extends to welding and non-metallics, including failure analysis and wear and corrosion testing, the focus of the visit was on Exceed’s wear testing capabilities. Jeff, who is a Chartered Professional Engineer, holds a metallurgy degree from Curtin University. His career prior to forming Exceed included employment in the former State Engineering Works and in the testing field with ETRS. Adam Dunning holds an Advanced Diploma in Metallurgy.
As an introduction to the visit Jeff gave a short presentation explaining the principles of the four main testing methods used at Exceed Consulting. These are the Dry Sand Abrasion test, Slurry Erosion test, Rubber Abrasion test and the Taber Abraser®.
The dry sand abrasion test operates by using a loaded rubber-tyred wheel to rub a stream of fresh standard silica sand against the surface of a test piece. Following ASTM G65, the material loss by abrasion after 30 minutes is measured by weight or volume. The test is standardised against D2 tool steel test coupons, which lose 36 mm3. By comparison, carbon steel loses around 120, and tungsten carbide weld overlay loses about 0.07 mm3. This test is a good predictor of comparative wear life in sliding abrasion, as occurs in ore chutes.
Sample preparation is important, and the test is affected by surface condition, porosity, cracks and inhomogeneity. Among the samples provided for inspection after testing, Jeff and Adam had included a couple of supposedly wear-resistant ceramics that showed higher wear than carbon steel. These demonstrated the folly of buying such ceramics on the basis of inadequate specifications such as “>92% alumina”. These examples demonstrated that many factors, including other components, porosity and firing temperature, are critical in determining wear resistance.
The slurry erosion test (ISO 15527) was developed for Ultra High Molecular Weight Polyethylene, but is also used for other materials. It rotates (1200 rpm) a spindle-mounted 75 x 25 x 6 mm sample in a temperature-controlled (25ºC) 30% 0.5 - 1 mm silica slurry for 24 hours, with mass loss being reported as the measure of wear. The sample can be mounted at various angles to simulate different service conditions.
The rubber abrasion test is a comparative test of a sample of rubber against a standard rubber. It is covered by several standards, including ASTM 5963, DIN 53516 and ISO 4649. In one common test configuration, the weighted 16mm dia. test pieces are abraded on P80 grit abrasive paper for a length of 40 m, with comparative weight loss reported. Wet testing is also possible, but is not covered by standards.
The Taber Abraser is a versatile test covered by numerous standards. Essentially it measures wear against a standardised grinding wheel. Various loading conditions can be applied, together with a range of wheels available depending on the material being tested. The test can be applied to materials as diverse as fabrics and leather, painted coatings and tiles, and through to solid metals.
Of the four tests demonstrated, the Taber Abraser is least in demand as its main use tends to be for quality control in manufacturing. Reflecting the current nature of demand in WA, most of Exceed’s clients for wear testing are interested mainly in quality checking on materials supplied to them. However, Exceed also offers detailed assessment of wear mechanisms and can undertake investigative studies.
The visitors greatly appreciated both the hospitality offered and the opportunity to see the interesting and specialised activities that go on, otherwise largely out of sight, in Perth’s suburban industrial precincts.