Effect of surface hardening conditions on susceptibility of fasteners to hydrogen embrittlement

Medcalf, John Steven

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https://hdl.handle.net/2142/90639 Copy

Description

Title

Effect of surface hardening conditions on susceptibility of fasteners to hydrogen embrittlement

Author(s)

Medcalf, John Steven

Issue Date

2016-04-27

Director of Research (if dissertation) or Advisor (if thesis)

Thomas, Brian G.

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• hydrogen embrittlement
• fasteners
• case hardened
• tapping screws
• surface hardened
• zinc electroplating

Abstract

The goal of this work is to establish the relationship between core hardness, case hardness, and case depth on susceptibility to hydrogen embrittlement of case hardened steel fasteners. While case hardened fasteners have been studied previously, there are currently no processing guidelines supported by quantitative data for fastener standards. Through sustained load and incremental step load embrittlement testing techniques, the susceptibility of case hardened steel tapping screws to internal and environmental hydrogen embrittlement is examined. Further characterization of the fastener samples through microhardness testing, microstructure review, and fracture surface examination allows the determination of susceptibility thresholds. It is shown that core hardness is the primary consideration for susceptibility. However, the fastener surface is prone to failure before the bulk section, up to the case depth, according to the case hardness. The zinc acid electroplating process used to process the fasteners in this study appeared not to induce internal hydrogen embrittlement. Post plating baking operations, however, are shown to lower the threshold strength for embrittlement in high-hardness notched square bars processed on the same plating line.

Graduation Semester

2016-05

Type of Resource

text

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http://hdl.handle.net/2142/90639

Copyright and License Information

Copyright 2016 John Medcalf

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