Development and Production of Artificial Test Swarf to Examine Wear Behavior of Running Engine Components - Geometrically Derived Designs

Subtractive manufacturing processes are usually accompanied by the occurrence of tiny
flakes and swarf, which later on cause severe wear and damage, especially in moving components
such as rolling or sliding bearings, pistons, etc. However, up until now, such detrimental effects
have hardly been investigated. One reason is the lack of a definition of a typical design of debris
particle. Therefore, the main goal of the project described in this paper was to elaborate a draft that
defines standardized test particles. It had to be evaluated whether test particles could be adequately
reproduced and whether they would reveal significant damage potential. Taking into account future
mass fabrication, Micro Powder Injection Molding (MicroPIM) was chosen as a production method.
Five different 3D designs of geometrically defined test particles were developed. The maximum size
of each design was 1167 mm in green state; however, all samples shrank in size during sintering.
Specially tailored feedstocks containing 42CrMo4 steel powders were used and the related molding,
debinding and sintering procedures were developed. All particle geometries and related mold inserts
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were developed using a commercial software routine for the layout of runner systems, gate locations
and ejector positions. The damage potential of the test particles was evaluated based on trials using
journal bearing and shift valve test rigs. Although only a moderate degree of damage potential could
be ascertained up until now, it can be expected that the artificial swarf will enable standardized wear
test procedures to be developed.