MIL-DTL-13924D
4.4.4 Hydrogen embrittlement relief treatment. When specified (see 6.2), ferrous
parts shall be baked in accordance with AMS 2759/9, table 1.
4.4.4.1 Hydrogen embrittlement relief test. Samples selected in accordance with
4.2.2 to determine the adequacy of the hydrogen embrittlement relief treatment,
shall be tested in accordance with ASTM F519. When specified (see 6.2), the
standard notched round bar specimen under load control described in annex A1, which
is a part of ASTM F519, shall be used. The lot shall be rejected if any coated
specimen develops any crack or fails by fracture as a result of the test.
5.
PACKAGING
5.1
Packaging.
Packaging requirements are not applicable to this specification.
6.
NOTES
(This section contains information of a general or explanatory nature that may be
helpful, but is not mandatory.)
6.1 Intended use. The black oxide coatings covered by this specification are
military unique. Black oxide coatings are used on munition cases and gun barrels.
These coatings are particularly suited for moving parts that cannot tolerate the
dimensional build up of a more corrosion resistant finish. They are not recommended
on parts going into long term storage. Sometimes, long term storage is required and
a protective preservative fluid is recommended or a desiccated package is utilized.
The coatings present a pleasing black appearance frequently employed for decorative
purposes or decrease in light reflection. A supplementary water displacing
preservative coating such as MIL-PRF-16173, grade 3 or comparable material which
will provide equal or superior corrosion protection may be specified.
CAUTION:
High strength steel (40 HRC or greater hardness)
may be subjected to "caustic embrittlement" that could
lead to spontaneous cracking if under internal or applied
stress during the blackening treatment.
6.2
Acquisition requirements.
Acquisition documents should specify the following:
(a) Title, number, and date of this specification.
(b) Class of coating (see 1.2).
(c) Issue of DoDISS to be cited in the solicitation, and if required, the
specific issue of individual documents referenced (see 2.2.1 and 2.3).
(d) Number of samples to be inspected from the lot of coated parts (see 4.2.2).
(e) Acceptance requirements prior to shipment of the coated parts, if
different (see 4.3).
(f) Bake ferrous parts in accordance with AMS 2759/9, table 1 (see 4.4.4).
(g) Use the standard notched round bar specimen under load control described
in annex A1, which is a part of ASTM F519 (see 4.4.4.1).
6.3
Miscellaneous notes.
6.3.l Dimensional change. Black oxide coatings on iron and steel should produce
no appreciable dimensional change of the treated piece. The dimensions shown on the
drawings are, therefore, the dimensions after the application of the coatings.
6
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