5 Jul Alloy 22 is a Ni-Cr-Mo alloy (Nickel-Chromium-Molybdenum) and is one of the most versatile corrosion resistant alloys used in industry today. ABSTRACT It is common practice to perform intergranular corrosion testing in accordance with ASTM (1) G28 on solid solution nickel alloys, e.g. UNS N . 13 Apr ASTM G – Designation: G 28 – 02 Standard Test Methods of Detecting Susceptibility to Inter.
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Intergranular Attack Testing – ASTM G28 – Colorado-Metallurgical-Services
The test method is not applicable to cast products. ASTM G28 was designed for nickel-based alloys, and a list of applicable alloys for methods A and B is in the standard. As 15 hours is a difficult test period in practice, and is only a minimum, conducting the test for 20 hours overnight means that the two tests are equivalent. There are other requirements in these standards over details that are not discussed in this document, and these should be followed, such as conducting bend tests. There are a number of recognised tests when it comes to the intergranular corrosion testing of corrosion resistant alloys CRA.
These environments are typically oxidizing and acidic e.
Figure 1 shows a sensitized microstructure, where the darker etched grain boundaries have a decoration of precipitates. The test solutions and exposures for some g2 intergranular corrosion tests. Corrosion rate, expressed in millimeters per year, can be calculated considering the original mass and surface area of the test pieces, their mass loss, the duration of the immersion and the density of the acid solution.
ISO is the most rigorous in terms of defining test methods, and says which alloys should use which test methods as follows: It has been used for the duplex stainless steel UNS Swhich has been used for nitric acid cooler tubes.
Conducting the Tests When a test has been selected, follow the detailed directions in that standard for making up the test solution, the preparation of test samples and the finish to be used. Table 1 below shows the various methods for four common standards: Peer reviewed only Published between: This document also points out which alloys the tests are intended for, and recommends the most appropriate test when awtm is specified.
ISO is specifically for duplex and atsm austenitic stainless steels, and recommends ageing at two different temperatures:. The effect of post weld surface treatments on the corrosion resistance of super duplex stainless steel welds in sea water Hence, it is normally only used for stainless steels intended for nuclear service, or another application involving nitric acid.
The test methods in Table 1 were designed with specific alloys in mind, but the proliferation of new CRAs has meant that the selection of a suitable test method is difficult. The results of such tests are applied widely as acceptance tests for parent and welded materials, and as such are essentially used to confirm the suitability of these materials for service.
SEP method 3 is a special environment only suitable for the Ni-Mo alloys, as described below, in section 4. Suggested test methods for different corrosion resistant alloys.
Alternatively, a welded test-piece in the as-welded condition may be tested. Proceedings of an international conference Oceanology: Referenced Documents purchase separately The documents listed below are referenced within the subject standard asym are not provided as part of the standard.
Resistance to Intergranular Corrosion of Nickel Rich Chromium Bearing Alloys
Proceedings of an international conference Diverless and Deepwater Techology: Test Samples Samples may be rectangular or cylindrical to suit the test vessel, but where a bend test is required, it is suggested that the sample be a minimum of mm long. SEP does not require ageing, although it might be required in a specification calling up this standard.
ASTM A was designed for austenitic stainless steels, specifically the series alloys. Sheriff’s Encyclopedic Dictionary of Applied Geophysics, fourth edition. ASTM G28 lists alloys and specifies the test exposure for each. In the case of nickel-rich, chromium-bearing alloys, the test method may be applied to wrought and weldments of products.
The specifications for bend testing are shown in Table 4. Where a bend test is required, the sample must be bent over a mandrel of a diameter asstm to the specimen diameter, without any cracking, as determined by inspection under a low power asmt and a microsection in any suspicious areas.
When a test has been selected, follow the detailed directions in that standard for making up the test solution, the preparation of test samples and the finish to be used. Get in Touch Contact us by Phone or Email to find out how we can help your industry.
This must be established independently by specific tests or by service experience. All bend tests require a tensile test machine or similar, with asym grips and sufficient strength to bend the strongest alloy.
Corrosione leghe di nichel con presenza di cromo astm g28
Link to Active This link will always route to the current Active version of the standard. Warning statements are given in 5. Just remember that these tests were devised for specific groups of alloys and should not be applied to all CRAs!