Application Examples

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Falex Miller abrasivity tests in clay slurries

WHY

In the brick production industry, components used for the processing equipment (mixing, molding, extrusion) suffer from abrasive wear by the clay slurries. Since this clay differs from site to site, the abrasion damage can differ also.  With this method, we evaluate not only material wear resistance, but can also define the abrasivity of the clay.

HOW

Miller slurry abrasivity tests are performed according to ASTM G75, comparing the slurry abrasion-corrosion damage to materials from the production environment, where a clay slurry causes progressive wear.

The Miller test is appropriate to perform a repeatable and realistic wear process, consisting of the combination of abrasive particle wear and corrosive interactions in the presence of some water.  The test method has been traditionally used to evaluate both slurry abrasivity (Miller Number) or material resistance against slurry abrasivity (SAR number) for applications such as pumps, materials in dredging, mining, etc.

Thanks to its specific design, the test machine creates a repeatable environment between the materials and the slurry, resulting in highly repeatable wear tests.  The evolution of wear, and a convenient comparison of wear resistance of materials AND abrasivity of a slurry, can be measured in one series of experiments.

Clays are mixed with water and some additional ingredients to obtain a 'flowing' slurry, so that the contact is refreshed on each stroke.  The metal parts are cut directly from the processing equipment, to use the as-produced hardmetal coating as the test piece. 

 

 

b2ap3_large_MillerPicture_nobackground Applications

RESULT 

  • Adapted Miller slurry tests are used to compare the abrasiveness of clay slurry with sand slurry or other clays.
  • There is some more variation in the wear results in clay, due to greater inhomogeneity of clay as a slurry.
  • Baseline information when changing the tool materials : will other materials resist the clay wear better ?
b2ap3_thumbnail_weight-loss-evolution_clay Applications b2ap3_thumbnail_SAR_clay-vs-sand Applications
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The need for an abrasion and an erosion method

WHY ? : Abrasion and erosion mechanisms are quite different from each other, and can lead to very different material behaviour.  For instance, a hard and brittle surface may be very resistant to abrasion, but sensitive to erosion under 90° impact. 

HOW ? : Using two separate test systems :

- ASTM G65 describes the method to rub solid particles tangentially over a material.  'Dry sand rubber wheel abrasion'.  ASTM G75 uses a similar motion, but reciprocating and in a wet slurry.  But it's still abrasion.

- ASTM G76 on the contrary describes how to impact with a gas flow carried stream of particles on a surface under varying angles, between 90° perpendicular impact and 15°.

RESULT : ductile vs. brittle materials behave very differently, depending on the impact angle of particles, and by extension, depending on whether it's abrasive vs. erosive conditions.

Afbeeldingsresultaat voor erosion ductile brittle

 

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Abrasion by powders during powder processing

WHY ?  : One issue in the pharmaceutical industry, is the abrasion of processing components for pressing the powders. The intensity of the abrasion phenomena strongly depends on the composition and size of the processed powders. Up to date there is no fixed procedure on how to evaluate such abrasion phenomena, in conditions that simulate the realistic process.

HOW ?  : A modification on the Falex Multispecimen machine was prepared to simulate powder pushing over a pressing disk. In the updated setup a knife - similar to the actual application - was attached to the machine. Powder is supplied and continuously refreshed from the center of the contact. This refreshment and distribution is essential to avoid attrition or poor repeatability.  After completion of a test, the wear mechanisms on both knife and disk are investigated by optical microscopy. Changes in the cutting tip were evaluated by comparing the tip angle before and after the tests with a confocal microscope. The wear damage was assessed by measuring the width of the scar of the knife before and after testing.

 

b2ap3_thumbnail_Falex-Multispecimen abrasion - Application examples | FACTLABS.ORG 

 

RESULT :

- A methodology was developed to evaluate the abrasion of components used for powder processing in the pharmaceutical industry.

- The wear mechanisms were assessed and correlated to the one met in the actual application.

- The use of coatings to improve the abrasion resistance and lifetime such components was considered.

 b2ap3_thumbnail_wear-on-knife abrasion - Application examples | FACTLABS.ORG

b2ap3_thumbnail_58HRC-beforetest-200-a abrasion - Application examples | FACTLABS.ORG b2ap3_thumbnail_HSS_50_2 abrasion - Application examples | FACTLABS.ORG

 

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