Mechanisms of Powder Metal, PM, Gear Failures

AGMA 944-A19

AGMA 944-A19


This information sheet describes many of the ways in which powder metal, PM, gear teeth can fail and recommends methods for reducing PM gear failures. It provides basic guidance for those attempting to analyze PM gear failures. The information sheet should be used in conjunction with ANSI/AGMA 1010 in which the gear tooth failure modes are defined. Similar definitions can also be found in ISO 10825 [1]. Although these standards are primarily focused on steel parts, they help investigators understand failures and investigate remedies.

This information sheet does not define “gear failure”. One observer's “failure” is another observer's “run-in.” There is no single definition of gear failure, since whether or not a gear has failed depends on the specific application.

The information presented in this document applies to spur and helical PM gears. However, with some exceptions the information also applies to other types of PM gears.


[The foreword, footnotes and annexes, if any, in this document are provided for informational purposes only and are not to be construed as a part of AGMA Information Sheet 944-A19, Mechanisms of Powder Metal, PM, Gear Failures.]

This information sheet provides a means to describe the appearance of powder metal gear teeth when they wear or fail. The study of powder metal gear tooth wear and failure has been hampered by the inability of two observers to describe the same phenomenon in terms that are adequate to assure uniform interpretation.

The term “gear failure” is subjective and a source of considerable disagreement. For example, a person observing gear teeth that have a bright, mirrorlike appearance may believe that the gears have “run-in” properly. However, another observer may believe that the gears have failed by polishing wear. Whether the gears should be considered failed or not depends on how much change from the original condition is tolerable.

This information sheet provides a common language to describe powder metal gear wear and failure and serves as a guide to uniformity and consistency in the use of that language. It describes the appearance of powder metal gear tooth failure modes and discusses their mechanisms, with the sole intent of facilitating identification of gear wear and failure. The purpose of the information sheet is to improve communication between users and manufacturers for failure and wear analysis. Since there may be many different causes for each type of powder metal gear tooth wear or failure, it is not possible in the information sheet to identify a single cause for each type of wear or failure, nor to prescribe all possible remedies.

The first draft of AGMA 944-A19 was made in February 2012. It was approved by the AGMA Technical Division Executive Committee in June 2019.


The following standards contain provisions which are referenced in the text of this information sheet. At the time of publication, the editions indicated were valid. All standards are subject to revision, and parties to agreements based on this document are encouraged to investigate the possibility of applying the most recent editions of the standards indicated.

  • ANSI/AGMA 1010-F14, Appearance of Gear Teeth – Terminology of Wear and Failure
  • ANSI/AGMA 6008-A98, Specifications for Powder Metallurgy Gears

ISBN: 978-1-64353-036-9

Pages: 30

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