ASTM G146-96

NOTICE: This standard has either been superseded and replaced by a new version or discontinued.
Contact ASTM International (www.astm.org) for the latest information.
Designation: G 146 – 96
Standard Practice for
Evaluation of Disbonding of Bimetallic Stainless Alloy/Steel
Plate for Use in High-Pressure, High-Temperature Refinery
Hydrogen Service
This standard is issued under the fixed designation G 146; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (e) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This practice describes a procedure for the evaluation of
disbonding of bimetallic stainless alloy/steel plate for use in
refinery high-pressure/high-temperature (HP/HT) gaseous hy-
drogen service. It includes procedures to (a) produce suitable
laboratory test specimens, (b) obtain hydrogen charging con-
ditions in the laboratory that are similar to those found in
refinery HP/HT hydrogen gas service for evaluation of bime-
tallic specimens exposed to these environments, and (c) per-
form analysis of the test data. The purpose of this practice is to
allow for comparison of data among test laboratories on the
resistance of bimetallic stainless alloy/steels to hydrogen-
induced disbonding (HID).
1.2 This practice applies primarily to bimetallic products
fabricated by weld overlay of stainless alloy onto a steel
NOTE 1—Open symbols—no disbonding reported. Filled symbols—
substrate. Most of the information developed using this prac-
disbonding reported.
tice has been obtained for such materials. The procedures
FIG. 1 Conditions of Hydrogen Partial Pressure and Temperature
described herein, may also be appropriate for evaluation of hot
with Demonstrated Susceptibility to Hydrogen Disbonding in
roll bonded, explosive bonded, or other suitable processes for
Refinery High-Pressure Hydrogen Service
applying stainless alloys on steel substrates. However, due to
the broad range of possible materials, test conditions, and
1.6 This standard does not purport to address all of the
variations in test procedures, it is up to the user of this practice
safety concerns, if any, associated with its use. It is the
to determine the suitability and applicability of these proce-
responsibility of the user of this standard to establish appro-
dures for evaluation of such materials.
priate safety and health practices and determine the applica-
1.3 This practice is intended to be applicable for evaluation
bility of regulatory limitations prior to use. See Section 6 for
of materials for service conditions involving severe hydrogen
additional safety information.
charging which may produce HID as shown in Fig. 1 for
2. Referenced Documents
stainless steel weld overlay on steel equipment (see Refs 1 and
2 in Appendix X1). However, it should be noted that this
2.1 ASTM Standards:
practice may not be appropriate for forms of bimetallic
G 111 Guide for Corrosion Tests in High-Temperature or
construction or service conditions which have not been ob-
High-Pressure Environment, or Both
served to cause HID in service.
E 3 Practice for Preparation of Metallographic Specimens
1.4 Additional information regarding the evaluation of bi-
2.2 ASME Standard:
metallic stainless alloy/steel plate for HID, test methodologies,
Boiler and Pressure Vessel Code Section V, Article 5, Tech-
and the effects of test conditions, materials, and welding
nique Two
variables, and inspection techniques is given in Appendix X1.
3. Terminology
1.5 The values stated in SI units are to be regarded as the
standard.
3.1 Definitions:
1 2
This practice is under the jurisdiction of ASTM Committee G-1 on Corrosion Annual Book of ASTM Standards, Vol 03.02.
of Metalsand is the direct responsibility of Subcommittee G01.05on Laboratory Annual Book of ASTM Standards, Vol 03.01.
Corrosion Tests. Available from American Society of Mechanical Engineers, 345 E. 47th St.,
Current edition approved Oct. 10, 1996. Published December 1996. New York, NY 10017.
Copyright © ASTM, 100 Barr Harbor Drive, West Conshohocken, PA 19428-2959, United States.
G 146
3.1.1 HID—a delamination of a stainless alloy surface layer 6.2 There are many types of test cell configurations which
from its steel substrate produced by exposure of the material to can be used to conduct evaluations of HID. This practice does
a hydrogen environment. not recommend or endorse any particular test cell design. Fig.
3.1.2 Discussion—This phenomenon can occur in internally 2 shows a schematic representation of a typical test cell
stainless alloy lined steel equipment by the accumulation of designed to conduct HID tests in HP/HT gaseous hydrogen
molecular hydrogen in the region of the metallurgical bond at environments. Other designs may also provide acceptable
the interface between the steel and stainless alloy surface layer performance. However, the typical components should include
produced by exposure to service conditions involving HP/HT the following:
hydrogen in the refinery hydroprocessing. 6.2.1 Metal Test Cell—The test cell should be constructed
from materials which have been proven to have high resistance
4. Summary of Practice
to hydrogen embrittlement and high-temperature hydrogen
4.1 Stainless alloy/steel specimens are exposed to a gaseous
attack under the anticipated test conditions. Materials with low
hydrogen containing environment at HP/HT conditions for resistance to these phenomena should be avoided. Typical test
sufficient time to produce hydrogen charging in the material.
cells for high-pressure hydrogen testing are constructed from
Following exposure, the specimens are cooled to ambient stainless steel (UNS S31600 or S34700) or nickel alloys (UNS
temperature at a controlled rate. The specimens are then held at
N10276 or N06625) in the solution annealed condition. Steel
room temperature for a designated period to allow for the vessels with stainless alloy exposed surfaces may also be
development of HID between the stainless alloy surface layer
suitable.
and the steel. Following the hold period, the specimens are 6.2.2 Closure and Seal—To facilitate operation of the test
evaluated for HID at this interface using straight beam ultra- cell, the closure should provide for rapid opening and closing
sonic methods with metallographic examination to confirm any
of the test cell while retaining reliable sealing capabilities for
HID found. The size and distribution of the disbonded re- hydrogen. This can include either metallic or nonmetallic
gion(s) are then characterized by this practice. Single or
materials with high resistance to thermal degradation and
multiple hydrogen exposure/cooling cycles can be conducted hydrogen attack.
and varying exposure conditions and cooling rates can be
6.2.3 Gas Port(s)—The gas port should be designed to
incorporated into this evaluation to provide assessment of the promote flow and circulation of the gaseous test environments,
disbonding characteristics of materials and service condition
inert gas purging, and evacuation as required to produce the
used for refinery process equipment containing HP/HT hydro- intended test environment. Usually two ports are used so that
gen containing environments.
separate flow-through capabilities are attained to facilitate
these functions.
5. Significance and Use
6.2.4 Electrical Feed-Throughs—High-temperature condi-
5.1 This practice provides an indication of the resistance or
tions are required in this practice. It is usually advantageous to
susceptibility, or both, to HID of a metallurgically bonded
stainless alloy surface layer on a steel substrate due to exposure
to hydrogen-containing gaseous environments under HP/HT
conditions. This practice is applicable over a broad range of
pressures, temperatures, cooling rates, and gaseous hydrogen
environments where HID could be a significant problem. These
procedures can be used to assess the effects of material
composition, processing methods, fabrication techniques, and
heat treatment as well as the effects of hydrogen partial
pressure, service temperature, and cooling rate. The HID
produced by these procedures may not correlate directly with
service experience for particular applications. Additionally, this
practice does not address the evaluation of high-temperature
hydrogen attack in the steel substrate. Typically, longer expo-
sure times at the test conditions must be utilized to allow for
the resistance to decarburization, internal blistering or crack-
ing, or both, to be evaluated.
6. Apparatus
6.1 Because this practice is intended to be conducted at high
pressures and high temperatures, the apparatus must be con-
structed to safely contain the test environment while being
resistant to the cumulative embrittling effects of hydrogen.
Secondly, the test apparatus must be capable of allowing (a)
introduction of the test gas, (b) removal of air from the test cell,
(c) uniform heating of the test specimens, and (d) cooling of
the specimens at controlled rates. FIG. 2 Typical Test Cell
G 146
utilize an internal heater to heat just the test specimens and the 9. Sampling
gaseous environment in the immediate vicinity of the speci-
9.1 The procedure for sampling stainless alloy bimetallic
men. Therefore, feed-throughs are usually needed to make
products should be sufficient to provide specimens that are
electrical contact with an internal resistance or induction
representative of the plate from which they are taken. The
heater. These feed-throughs must also provide (a) electrical
details of this procedure should be covered in product or
isolation from the test cell and internal fixtures and (b)
purchase specifications and are not covered in this practice.
maintain a seal to prevent leakage of the test environment. If
9.2 Sampling of the test environment is recommended to
external heaters are used, no electric feed-throughs are re-
confirm that the test procedure is in conformance with this
quired.
practice and attains the intended test conditions. The frequency
6.2.5 Electric Resistance or Induction Heater(s)—Either
of environmental sampling should be covered in applicable
internal or external heaters can be used to obtain elevated
product, purchase, or testing specifications, or both. As a
temperature. For lower temperatures (<300°C), external heat-
minimum requirement to be in compliance with this practice,
ing of the test cell is typically more convenient but may limit
sampling of the test environment shall be conducted at the start
cooling rates since they heat the entire vessel. For high
of testing in a particular apparatus and when any element of the
temperatures (>300°C), an internal heater is commonly used to
test procedure or test system has been changed or modified.
heat only the test specimen and the gaseous environment in the
10. Test Specimens
vicinity of the test specimens to limit power requirements and
problems with high-temperature sealing and pressure contain-
10.1 The standard test specimen is shown in Fig. 3. It
ment.
consists of a cylindrical section machined from a stainless
alloy/steel plate sample fabricated with methods to be used in
7. Reagents
the actual equipment fabrication under consideration. The
7.1 Purity of Reagents—Low oxygen gases (<1 ppm) shall
dimensions of the specimen shall be 73 6 2 mm in diameter
be used in all tests.
and 45 6 2 mm thick. However, for thinner cross-section
materials, the thickness of the specimen may be reduced to
8. Test Conditions
match the plate thickness being evaluated.
8.1 The test environment is based on attaining conditions of
10.2 The thickness of the stainless alloy surface layer to be
high-pressure hydrogen gas. The test temperature and hydro-
evaluated shall be nominally the same as that being used in the
gen gas pressure are selected to simulate those conditions
process to be evaluated.
found in refinery hydrogen-containing environments. These
10.3 A stainless alloy overlay weld shall be applied to the
typically range from 14 to 20 MPa hydrogen gas pressure and
sides of the specimen to promote through-thickness diffusion
temperature from 300 to 500°C depending on actual refinery
of hydrogen following exposure. If the bimetallic plate has not
service conditions under consideration, but may be selected
already been heat treated following fabrication, the entire
over the range of conditions in Fig. 1 that have been shown to
specimen shall be heat treated for the time and temperature and
produce HID.
with a similar cooling rate from the heat-treatment temperature
8.2 One of the major variables involved in testing for HID
normally required for the bimetallic product. However, if the
of stainless alloy/steel plate is the cooling rate selected for
bimetallic plate sample has already been heat treated, the side
evaluation. Cooling rates as high as 260°C/h have been utilized
overlay weld shall be heat treated at a temperature of 600°C
to intentionally produce disbonding for the purposes of inves-
maximum, with a similar cooling rate used for the bimetallic
tigating hydrogen disbonding mechanisms. The cooling rate
adopted most readily for qualification testing is 150°C/h.
Slower cooling rates can be utilized for the purposes of
simulating the effects of particular shutdown conditions expe-
rienced in refinery equipment. The cooling rate from the test
temperature to 200°C shall be controlled and maintained
constant while the specimens are in the high-pressure hydrogen
environment. Once the temperature of the specimens reaches
200°C, the hydrogen gas environment may be removed and
replaced with inert gas followed by opening of the test vessel
to air. Subsequent cooling from 200°C shall be conducted such
that the specimens are cooled to ambient temperature by forced
air of 30 to 60 m/min around all sides of the specimens while
they are supported on ceramic blocks or spacers. If linear
cooling can not be obtained in this range with forced air,
specimens may be misted with water to provide additional
control.
8.3 If simulation of actual conditions is required, these
conditions may be modified to better represent the intended
refinery service conditions of interest. However, these condi-
tions must be reported. See Section 13. FIG. 3 Test Specimen Configuration
G 146
product prior to testing.
10.4 The only steel surface on the specimen is the one
opposite the alloy surface being evaluated in the test. The
purpose of the side overlay is to limit diffusion of hydrogen in
the radial direction during and after cooling of the specimen to
ambient conditions. The side overlay weld produces conditions
for diffusion of hydrogen from the test specimen in which
diffusion occurs primarily in th
...