Evaluating abrasive wear resistance of extruder tooling materials using the dry sand rubber wheel abrasion test

Abstract

A series of experiments was performed on groups of samples made from materials currently used to manufacture tooling for extruders to determine if the ASTM G65 dry sand rubber wheel abrasion test could be used as an accelerated test to evaluate candidate materials. Samples were tested in the heat treated condition and after surface modification by plasma ion nitriding. The range of materials tested included medium and high alloy steels and steel bonded carbide composites. The abrasives used were AFS 50/70 test sand and Dresser Glasgrain crushed fused silica.

Evaluation of test wear scars and wear debris from the tests using AFS 50/70 showed that delamination was the primary wear mechanism for the composite materials, with some ploughing and microcutting, while ploughing and microcutting were the primary mechanisms in the wear of the steels. Evaluation of parts made from a composite material which were removed from service indicated that matrix erosion was the primary wear mechanism. Tests with Glasgrain fused silica as the abrasive yielded wear scars with the same morphology as the parts returned from service, but the very poor flow characteristics of this material caused inconsistency in the supply of this abrasive to the contact region.

Interrupted tests showed that the wear rate was constant for the steels in the non-nitrided condition. After nitriding, the wear rate increased with test duration. The nitriding was found to act as a barrier coating providing an initial period of very low wear until the nitride layer is broached. The wear rate then increases to approximate the wear rate of the non-nitrided samples.

It was found that the friction force alters the location of the maximum normal force, shifting the point of greatest contact force toward the entry end of the wear scar.