Значение и использование

5.1 Plating/coating Processes—This test method provides a means by which to detect possible hydrogen embrittlement of steel parts during manufacture by verifying strict controls during production operations such as surface preparation, pretreatments, and plating/coating. It is also intended to be used as a qualification test for new plating/coating processes and as a periodic inspection audit for the control of a plating/coating process.

5.2 Service Environment—This test method provides a means by which to detect possible hydrogen embrittlement of steel parts (plated/coated or bare) due to contact with chemicals during manufacturing, overhaul and service life. The details of testing in a service environment are found in Annex A5.

Область применения

1.1 This test method describes mechanical test methods and defines acceptance criteria for coating and plating processes that can cause hydrogen embrittlement in steels. Subsequent exposure to chemicals encountered in service environments, such as fluids, cleaning treatments or maintenance chemicals that come in contact with the plated/coated or bare surface of the steel, can also be evaluated.

1.2 This test method is not intended to measure the relative susceptibility of different steels. The relative susceptibility of different materials to hydrogen embrittlement may be determined in accordance with Test Method F1459 and Test Method F1624.

1.3 This test method specifies the use of air melted AISI E4340 steel per SAE AMS-S-5000 (formerly MIL-S-5000) heat treated to 260 to 280 ksi (pounds per square inch ×1000) as the baseline. This combination of alloy and heat treat level has been used for many years and a large database has been accumulated in the aerospace industry on its specific response to exposure to a wide variety of maintenance chemicals, or electroplated coatings, or both. Components with ultimate strengths higher than 260 to 280 ksi may not be represented by the baseline. In such cases, the cognizant engineering authority shall determine the need for manufacturing specimens from the specific material and heat treat condition of the component. Deviations from the baseline shall be reported as required by 12.1.2. The sensitivity to hydrogen embrittlement shall be demonstrated for each lot of specimens as specified in 9.5.

1.4 Test procedures and acceptance requirements are specified for seven specimens of different sizes, geometries, and loading configurations.

1.5 Pass/Fail Requirements—For plating/coating processes, specimens must meet or exceed 200 h using a sustained load test (SLT) at the levels shown in Table 3.

TABLE 1 Lot Acceptance Criteria for Notched Specimens

Type

Item

Sampling of
Each Lot

Requirement/Method

1

Tensile Strength

4 each

Test Method E8. Tensile strength of each specimen must be within 10 ksi of the average.

1 

Hardness^A

5 %

51 to 53 HRC per Test Methods E18.
 Round the average of
 three readings per
 specimen per Practice
 E29.

1 

Dimensions

100 %

Meet tolerances of
 corresponding
 drawings. Notch
 dimension verified with
 shadow graphic
 projection at 50 to
 100× or equivalent.

1 

Notched Fracture Strength (NFS)

10 ea

Test Methods E8/E8M. NFS of each specimen
 must be within 10 ksi
 of the average.

1c

Self-loading
 notched round
 specimen bend
 fixture, Fig. A2.7

10 ea

Alternate: The number of
 turns of the loading
 bolt, which is required
 to produce fracture in
 each specimen, must be
 within 5 % of the
 average.

1d

Self-loading
 notched C-Ring
 bend fixture,
 Fig. A2.8

10 ea

Alternate: The change in
 diameter at fracture
 load for each specimen
 must be within 0.008
 inches of the average.

^A If the hardness requirements of any of the sampled specimens are not satisfied, only those specimens of the lot that are individually inspected for conformance to these requirements shall be used for testing.TABLE 2 Electroplating Bath Compositions and Operating Conditions for Sensitivity Test

Item

Treatment A

Treatment B

Bath composition:

Range

Optimum

 

 Cadmium (as CdO)

2.9 to 5.5 oz/gal (22 to 41 g/L)

4.5 oz/gal (33.7 g/L)

same as Treatment A

 Total Sodium cyanide
  (NaCN)

12.0 to 16.0 oz/gal (89.9 to 120 g/L)

14 oz/gal (104 g/L)

same as Treatment A

 Ratio NaCN to CdO

2.8/1 to 6.0/1

3.0/1

same as Treatment A

 pH

12.0 or greater

12.0

same as Treatment A

 Temperature

70–90°F (21–32°C)

75°F (24°C)

same as Treatment A

 Sodium hydroxide
  (NaOH)^A

1.0 to 3.2 oz/gal (7.5 to 24.0 g/L)

2.5 oz/gal (18.7 g/L)

same as Treatment A

 Brightener such as
  Colcad 100^B or
  equivalent

Manufacturer's suggested range

None

 Electroplating current

10 A/ft²  (108 A/m²)

60 A/ft²  (645 A/m ²)

 Electroplating time

30 minutes

6 minutes

Baking

 

 

 

 Baking temperature

375 ± 25°F (190 ± 14°C)

same as Treatment A

 Baking time: Type 1
  Specimen

Do Not Bake

23 h

 Baking time: Type 2a
  Specimen

8 h

23 h

Chromate Treatment^C

Yes

same as Treatment A

^A Addition of sodium hydroxide may not be required on solution makeup, since the addition of 1 oz/gal of cadmium oxide is equivalent to 0.6 oz/gal of free hydroxide.^B The sole source of manufacture of Colcad 100 known to the committee at this time is Columbia Chemical in Brunswick, Ohio, www.columbiachemical.com. If you are aware of alternative manufacturers, please provide this information to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of the responsible technical committee, which you may attend.^C After baking, the specimens shall be dipped into any appropriate chromate conversion coating solution for minimum time that will produce an adherent and continuous coating as described in AMS-QQ-P-416 Type II.TABLE 3 Pass/Fail Loading Requirements of Test Specimens

Type 1a, 1b, 1c, 1d, 1e

75 % of the tensile or bend NFS (Table 1).

Type 2a

92 % of the Test Methods E8/E8M, E4 ultimate strength, obtained by deflecting a 2.300-inch diameter O-Ring specimen with a 2.525-inch stressing bar.

1.5.1 The loading conditions and pass/fail requirements for service environments are specified in Annex A5.

1.5.2 If approved by the cognizant engineering authority, a quantitative, accelerated (≤ 24 h) incremental step-load (ISL) test as defined in Annex A3 may be used as an alternative to SLT.

1.6 This test method is divided into two parts. The first part gives general information concerning requirements for hydrogen embrittlement testing. The second is composed of annexes that give specific requirements for the various loading and specimen configurations covered by this test method (see section 9.1 for a list of types) and the details for testing service environments.

1.7 The values stated in the foot-pound-second (fps) system in inch-pound units are to be regarded as standard. The values given in parentheses are mathematical conversions to SI units that are provided for information only and are not considered standard.

1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.