hidrogen embrittlemnet in fastener 3

[limct]

Is there a way/test to find out if a screw has a risk of hydrogen embrittlement attack?

Best regards,
ct

 

[digger200]

the only way I know would to be torque it up, leave it for a while then tap it with a hammer.

 

[metengr]

limct;
I know there are limited standard tests (an actual ASTM Standard) to evaluate susceptibility of the material to hydrogen assisted cracking that are expensive and involved because they require laboratory testing/analysis.

Is this for a particular application where you had a failure or are just looking to evaluate materials for use in a particular environment?

 

[swall]

Limct: there are ways to mitigate your risk. One is to avoid fasteners in excess of RC 30. A second is to avoid electroplating and use an organic coating instead.

 

[dbooker630]

It is important with any structural bolt to ensure that it has been sufficiently tempered. One test would be the Tempering Temperature Audit Test called out in SAE J1199.

I'm not sure what class of fasteners you are dealing with, but the 12.9 class fasteners are considered highly susceptible to hydrogen embtittlement. This class has a hardness of 38-44 HRC. The 12.9 fasteners are governed by ASTM F568M or ISO 898-1.

Mechanical testing involves first determining the ultimate torque of your application, then loading the fastener to 80% of its value (simulate your application), maintaining for 48 hours, reapplying test torque, then visually examining for cracks (stereomicroscope works well).

 

[CoryPad]

Here are some standards that cover this subject:

ASTM F 2078 – 01 Standard Terminology Relating to Hydrogen Embrittlement Testing

ASTM F 1624 – 00 Standard Test Method for Measurement of Hydrogen Embrittlement Threshold in Steel by the Incremental Step Loading Technique

ASTM F 519 Test Method for Mechanical Hydrogen Embrittlement Testing of Plating Processes and Aircraft Maintenance Chemicals

SAE/USCAR-5 AVOIDANCE OF HYDROGEN EMBRITTLEMENT OF STEEL

SAE/USCAR-7 DEEMBRITTLEMENT VERIFICATION TEST

ISO 9587 Metallic and other inorganic coatings -- Pretreatments of iron or steel to reduce the risk of hydrogen embrittlement

ISO 9588 Metallic and other inorganic coatings -- Post-coating treatments of iron or steel to reduce the risk of hydrogen embrittlement

ISO 15330 Fasteners -- Preloading test for the detection of hydrogen embrittlement -- Parallel bearing surface method

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[israelkk]

For military and aerospace use here is a quote as appear in QQ-P-416F (Cadmium plating)

4.6.4 Hydrogen embrittlement relief test.
4.6.4.1 Specimens. Specimens (4.5.3) plated with the parts lot shall have the same supplementary treatment as the parts and shall be subjected to a sustained tensile load equal to 75 percent of the notched ultimate tensile strength of the material. The specimens shall be subjected to the sustained load for not less than 200 hours, then examined for compliance with 3.3.4.

4.6.4.2 Fasteners. Externally threaded or grooved fasteners which can be loaded in tension by an axial application of a load up to 20,000 pounds or reasonable load limits of test equipment, shall be tested as specified in MIL-STD-1312-5. When the load requirement is greater than the reasonable
limits of the test equipment, the notched specimen procedure (4.6.4.1) shall be used. Internally threaded fasteners shall be tested as specified in MIL-STD-1312-14. The minimum test load shall be 85 percent of the minimum
ultimate tension load specified in the end product specification. The load shall be sustained for not less than 72 hours. The fasteners shall be examined for conformance to 3-3.4.