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Corrosion of metals and alloys - Test method for isothermal-exposure oxidation testing under high-temperature corrosion conditions for metallic materials
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Basic data
| Standard ID | GB/T 38430-2019 (GB/T38430-2019) |
| Description (Translated English) | Corrosion of metals and alloys - Test method for isothermal-exposure oxidation testing under high-temperature corrosion conditions for metallic materials |
| Sector / Industry | National Standard (Recommended) |
| Classification of Chinese Standard | H25 |
| Classification of International Standard | 77.060 |
| Word Count Estimation | 18,172 |
| Date of Issue | 2019-12-31 |
| Date of Implementation | 2020-07-01 |
| Quoted Standard | GB/T 1598; GB/T 9258.3-2017; GB/T 13298; GB/T 16701; GB/T 18036; JJG 141; ISO 26146 |
| Adopted Standard | ISO 21608-2012, MOD |
| Issuing agency(ies) | State Administration for Market Regulation, China National Standardization Administration |
| Summary | This standard specifies the equipment, gas supply, sample, test process, calculation of mass change, analysis of mass change, evaluation of sample after test and test report, etc. for isothermal exposure oxidation test of metal materials under high temperature corrosion conditions. This standard applies to continuous (without cooling the sample during the test, only weighing the sample after the test) and discontinuous (during the test in a predetermined but not necessarily Cool the sample at a few regular time points and weigh each sample in series) isothermal exposure test. This standard does not apply to the thermal cycle oxidation test of metal materials under high temperature corrosion conditions with gas (to accelerate high temperature corrosion, the samples are frequently and regularly cooled, and the mass of each sample is weighed in series). |
GB/T 38430-2019: Corrosion of metals and alloys - Test method for isothermal-exposure oxidation testing under high-temperature corrosion conditions for metallic materials
---This is a DRAFT version for illustration, not a final translation. Full copy of true-PDF in English version (including equations, symbols, images, flow-chart, tables, and figures etc.) will be manually/carefully translated upon your order.
Corrosion of metals and alloys - Test method for isothermal-exposure oxidation testing under high-temperature corrosion conditions for metallic materials
ICS 77.060
H25
National Standards of People's Republic of China
Corrosion of metals and alloys at high temperatures
Test method for isothermal exposure oxidation under corrosive conditions
(ISO 21608.2012, MOD)
Published on December 31,.2019
2020-07-01 implementation
State Administration of Market Supervision and Administration
Issued by the National Standardization Management Committee
Contents
Foreword Ⅲ
1 Scope 1
2 Normative references 1
3 Terms and definitions 1
4 Device 2
5 Gas supply 3
6 Sample 3
7 Test process 4
8 Calculation of mass change 6
9 Analysis of quality changes 8
10 Evaluation of the sample after the test 9
11 Test report 9
Appendix A (informative appendix) Correspondence between this standard and ISO 21608.2012 chapter number 11
Appendix B (informative appendix) The technical differences between this standard and ISO 21608.2012 and their causes 12
Appendix C (informative appendix) GB/T 9258.3-2017 abrasive grain grade and its particle size distribution 13
Foreword
This standard was drafted in accordance with the rules given in GB/T 1.1-2009.
This standard adopts a redrafting method to modify the use of ISO 21608.2012 "Corrosion of metals and alloys. Metal materials are corroded at high temperatures.
Test method for isothermal exposure oxidation under
Compared with ISO 21608.2012, this standard has more structural adjustments. Appendix A shows this standard and ISO 21608.2012.
Correspondence list of chapter number.
There are technical differences between this standard and ISO 21608.2012, and the clauses involved in these differences have been passed on the outer margin
The placed vertical single line (|) is marked, and Appendix B gives a list of corresponding technical differences and their causes.
This standard was proposed by China Iron and Steel Association.
This standard is under the jurisdiction of the National Steel Standardization Technical Committee (SAC/TC183).
This standard was drafted by. China Aviation Development Institute of Beijing Aeronautical Materials, Metallurgical Industry Information Standardization Institute.
The main drafters of this standard. Zhang Xiaoyun, Hou Jie, Chang Wei, Li Qian, Zhang Huanhuan.
Corrosion of metals and alloys at high temperatures
Test method for isothermal exposure oxidation under corrosive conditions
1 Scope
This standard specifies the equipment, gas supply, samples, test process, and isothermal exposure oxidation test of metal materials under high temperature corrosion conditions.
Calculation of quality change, analysis of quality change, evaluation of sample after test, test report, etc.
This standard applies to the continuity of metal materials under high-temperature corrosion conditions with gas (the sample is not cooled during the test, only after the test
Measure the quality of the sample) and discontinuous (cool the sample during a few predetermined points during the test but not necessarily regular, and series
Weigh each sample) isothermal exposure test.
This standard does not apply to the thermal cycle oxidation test of metallic materials under high-temperature corrosion conditions with gas (to accelerate high-temperature corrosion, frequent and frequent
Cool the samples regularly and weigh each sample in series).
2 Normative references
The following documents are essential for the application of this document. For dated reference documents, only the dated version applies to this article
Pieces. For the cited documents without date, the latest version (including all amendments) applies to this document.
GB/T 1598 platinum rhodium 10-platinum thermocouple wire, platinum rhodium 13-platinum thermocouple wire, platinum rhodium 30-platinum rhodium 6 thermocouple wire
GB/T 9258.3-2017 Abrasive particle size analysis for coated abrasives Part 3.Determination of particle size composition of fine powder P240~P2500
(ISO 6344-3.2013, MOD)
GB/T 13298 Metal microstructure inspection method
GB/T 16701 Measuring method of thermoelectromotive force of precious metal and cheap metal thermocouple wire
GB/T 18036 Thermoelectric force measurement method of platinum rhodium thermocouple filament
JJG141 precious metal thermocouple for work
ISO 26146 Corrosion of metals and alloys. Metallurgical test method for samples after exposure test in high temperature corrosive environment (Corrosionof
metalsandaloys-Methodformetalographicexaminationofsamplesafterexposuretohigh-tempera-
turecorrosiveenvironments)
3 Terms and definitions
The following terms and definitions apply to this document.
3.1
Oxide scale
The surface oxide film and corrosion products generated on the surface of the sample due to high temperature corrosion.
3.2
Adhering scale adherentscale
The scale attached to the surface of the sample after cooling.
3.3
Peeled scale spaledscale
Scale peeled from the surface of the sample.
3.4
Gross mass change
The change of the sum of the mass of the sample and the collected scale after cooling and the initial mass of the sample before the test.
3.5
Net quality change netmasschange
The change of the sample mass after cooling (not including scale peeling) and the initial mass of the sample before the test.
3.6
High-temperature corrosion
Corrosion above the dew point temperature (at least 100°C) of the liquid phase in the environment.
3.7
Breakaway
The rapid increase in corrosion rate caused by the transition from the formation of protective scales to the formation of non-protective scales.
4 Equipment
4.1 Equipment design
4.1.1 The equipment shall include a temperature adjustment device capable of heating the sample uniformly at a constant temperature. The heating device should be equipped with
Test unit (referred to as closed system) with air isolation. A humidity regulator should be used to ensure that the supplied gas can be kept at a specific humidity
Degree, and use a hygrometer to monitor. The gas supply is controlled by a gas flow meter. See the schematic diagram of the basic design of a closed device
figure 1.
Explanation.
1 --- gas supply port;
2 ---Gas flow meter;
3 ---valve;
4 --- Humidity regulator;
5 ---hygrometer;
6 --- heating device containing non-equilibrium gas mixture catalyst;
7 --- heating area with heating belt;
8 --- heating device;
9 --- sample room;
10---Sample;
11---sample holder;
12---thermocouple;
13---power/temperature control device;
14---gas discharge port;
15---Measurement device.
Figure 1 Schematic diagram of the basic design of a closed device
4.1.2 The design of the heating device should ensure that the sample room is isolated from the external environment.
4.1.3 The air flow through the sample should be continuous and the flow rate is within the specified range.
4.1.4 The sample room should not use materials that react with the test environment during the test to change the composition of the test environment.
4.1.5 If it is not possible to use a closed test system with a sample chamber, it can also be tested in a non-closed system in contact with laboratory air.
Atmospheric humidity should be recorded, the temperature should be kept constant in the laboratory, and should not be affected by weather conditions.
4.1.6 Before the test heating, an independent and movable thermocouple can be used to verify the heating furnace to determine the size of the uniform temperature zone in the heating furnace.
4.1.7 The temperature adjustment device should be able to ensure that the temperature of the sample is kept within the allowable range specified in Table 1.
Table 1 Allowable deviation of sample temperature
Temperature range/℃ ≤300 >300~600 >600~800 >800~1000 >1000~1200 >1200
Temperature deviation/℃ ±2 ±3 ±4 ±5 ±7 as per agreement
4.1.8 The thermocouple for the heating device used for temperature control shall meet the following requirements.
a) The material of the thermocouple should be able to meet the requirements for use at the test temperature;
b) Under the premise that the power of the heating device is unchanged, it is recommended that the diameter of the thermocouple wire be as small as possible.
4.2 Temperature monitoring
4.2.1 A suitable device should be used to measure the temperature, and a suitable thermocouple should be selected according to GB/T 1598.The device should be in accordance with the control specified in 4.1
Thermocouple is independent. It is recommended to use K-type thermocouple (nickel-chromium-nickel aluminum) within 800℃, and S-type thermocouple (platinum rhodium 10-
Platinum) and R-type thermocouples (platinum rhodium 13-platinum), B-type thermocouples (platinum rhodium 30-platinum rhodium 6) above 1100℃ is recommended. Should be attached to the surface of the sample
Place a thermocouple near and calibrate according to 4.2.2 and 4.2.3.If due to environmental factors the thermocouple cannot be placed near the sample surface.
4.2.2 The temperature of the sample shall be calculated according to the calibration of the heating furnace by using a blank sample under an inert environment and a suitable temperature measurement method
degree. A thermocouple should be drawn from each batch for calibration. The thermocouple calibration should be according to GB/T 16701, GB/T 18306 or JJG141
Regulations.
4.2.3 If the stability of the thermocouple cannot be determined, it should be recalibrated annually before use, or before and at the end of each test
calibration.
4.2.4 The thermocouple should be able to meet the temperature of the sample within the range specified in Table 1, the thermocouple should be in a fixed position and as close as possible to the sample.
4.2.5 The thermocouple wire shall be protected by thermocouple bushing. Thermocouple bushings should be able to be used at the test temperature and test environment.
5 Gas supply
5.1 The gas supply system shall be able to supply test gas to the sample chamber at a constant flow rate.
5.2 A gas flow meter should be used to monitor the gas flow. The flowmeter should be placed close to the entrance of the sample chamber, but when using humidity adjustment
When the device is used, the flow meter should be placed upstream of the humidity regulator.
5.3 When using a humidity regulator, the humidity regulator should be able to adjust the humidity to the desired value. Unless otherwise specified, conductivity should be used
Deionized water below 1μS/cm. To prevent condensation, the temperature in the space between the humidity regulator and the sample chamber should be kept above the dew point.
5.4 When the gas is humidified, the water vapor content should be tested. Test methods include measuring with a hygrometer in front of the sample chamber, or in the exhaust gas
Test the water content after condensation, or measure the water consumption in the humidifier during the test.
5.5 When testing in air, it is recommended to use a specific humidity of 20g/kg (that is, the mass fraction of water in the air). The specific humidity is at 25℃
The relative humidity under (dew point) is 100%, which can be obtained by bubbling in a water bath at 25℃. After consultation between the supply and demand sides, other humidity can also be used.
6 Sample
6.1 In order to analyze the oxidation kinetics of the material, multiple samples with different exposure times are required. It is recommended to use 2 tests for each exposure time
In addition, there are at least 4 sampling times that vary with time, such as 10h, 30h, 100h, 300h, and 1000h.
6.2 The shape of the sample should be plate, disc or cylinder, the surface area should not be less than 300mm2, and the thickness should not be less than 1.5mm. After both supply and demand
Negotiations may also use other sample shapes and sizes.
6.3 The surface of the sample should be mechanically polished to ensure that the cutting layer is removed. The final grinding and polishing of the sample surface should use the average particle diameter of about
For 15μm abrasive, P1200 abrasive that meets the requirements of GB/T 9258.3-2017 can be used (see Appendix C for abrasive particle size distribution). If
Relevant parties require the use of other surface grinding and polishing methods, should describe the conditions of surface grinding and polishing.
6.4 At the final stage of sample preparation, slight chamfering should be performed to avoid abnormal phenomena caused by the sharp edges of the sample.
6.5 Marking, stamping and grooving on the sample surface shall not cause deformation. The identification of the sample should be based on the record of the relative position of the sample in the sample chamber,
However, holes and/or fiducial marks supporting the specimen are allowed. When it is necessary to punch holes in the sample in order to support the sample, the hole should be ground and polished in the final
Or before applying the coating, and holes should be considered when calculating the sample surface area.
6.6 Isopropanol or ethanol should be used to clean the sample ultrasonically, and then dried. If the sample may absorb a lot of water and other environmental pollution
It is recommended to store the cleaned samples in a desiccator before weighing and exposure testing.
6.7 Before the exposure test, the sample size should be tested in at least 3 positions on the sample, and the accuracy of the measuring instrument should be ±0.02mm.
6.8 The sample should be weighed before the exposure test. Weighing should be no less than 2 times, and the mass difference between the two weighings should be no more than 0.05mg.
7 Test process
7.1 Support of the specimen
The sample should be supported according to the following rules.
a) The sample support material should not react at the test temperature. The contact area between the specimen and the support should be as small as possible.
b) The sample holder should be able to collect the scale peeled off during the test or during the cooling process after the test.
c) When testing multiple samples at the same time, only one sample is placed on each bracket to ensure that the scale of the sample can be collected.
d) The main surface of the sample should be able to fully contact the test atmosphere and not be blocked by the sample holder.
e) Examples of sample holders and schematic diagrams of sample placement are shown in Figures 2 to 4.
f) When the reactants are exhausted in the test environment, the hole or groove can be made in the lower region of the side of the sample holder
improve.
g) When only considering the net change in mass, it is allowed to put multiple samples into the same sample holder.
Explanation.
1---High purity corundum tube used to support the sample;
2---Sample.
Note. This design is not suitable for rapid heating and cooling.
Figure 2 The basic layout of the sample holder and sample placement --- tube design
Explanation.
1---hole.
Figure 3 The basic layout of the sample holder and sample placement-round crucible
Explanation.
1---hole;
2---Corundum sticks.
Figure 4 The basic layout of the sample holder and sample placement-rod support design
7.2 Test environment
7.2.1 The gas flow rate should be high enough to ensure that no serious exhaustion of reactants occurs. At the same time, the air flow should be slow enough to ensure
The gas mixture is preheated, and in some cases it should be ensured that the gas mixture is in equilibrium. The gas flow rate should be large enough to ensure the test gas
The body can completely replace the atmosphere in the sample chamber 3 times or more within 1 h.
7.2.2 When using an air test in a closed test system, the humidity should be controlled according to the requirements of Chapter 5.
7.2.3 When testing in the air environment of a non-closed test system, it should be noted that the humidity of the laboratory will depend on the geographic location and weather of the laboratory
The conditions vary. These changes may greatly affect the test results. Under this test condition, the test time should be recorded
Atmospheric humidity in the laboratory.
7.2.4 When testing in other environments, the humidity should be specified and measured.
7.3 Heating method
The following heating methods should be used.
a) The samples with brackets should be placed in the heating furnace at room temperature or test temperature. The temperature of the sample placed in the heating furnace shall be determined through negotiation between the supplier and the buyer
degree. When placed at room temperature, the time when the furnace is heated to the test temperature should be recorded.
b) When the sample is placed in an unheated heating furnace, wait for the gas to fill the heating furnace before heating. When testing in a humidified environment, the sample
Humidification is not allowed until the temperature in each part of the chamber exceeds 100°C.
c) When the sample is placed in the heated furnace, inert gas should be introduced during the process.
d) Appropriate heating methods should be used to ensure that the sample temperature does not exceed the upper limit of the allowable range specified in Table 1.
e) For the discontinuous exposure test, the same heating method as the first entry into the furnace should be used each time the sample is re-entered into the furnace.
7.4 Test period
7.4.1 When the sample temperature exceeds 97% of the set test temperature Tdwel (measured in Kelvin), it is defined as the start of the test.
7.4.2 When the sample temperature is lower than 97% of the set test temperature Tdwel (measured in Kelvin), it is defined as the test termination.
7.4.3 The test period is related to the intended application and is determined by consultation between the supplier and the buyer. Because the phenomena observed during short-term exposure may
The test will not continue to appear, and the test related to long-term service conditions, the exposure time should not be less than 300h.
7.5 Sample cooling
7.5.1 The sample with bracket should be taken out of the heating furnace at the test temperature or cooled to below 100℃, and the sample shall be determined by the supplier and the buyer through negotiation.
Take out the temperature. When taken out below 100 ℃, the time to cool to 100 ℃ should be recorded.
7.5.2 When the sample is cooled in the heating furnace, it should be continuously ventilated. When testing in a humidified environment, the temperature at the lowest point in the sample chamber should be
When the temperature drops to.200℃, stop humidification.
7.5.3 When the sample is taken from the hot heating furnace, inert gas should be introduced during the removal process.
8 Calculation of mass change
8.1 General
To define the oxidation kinetics, it is necessary to determine the change in sample mass. There should be backup samples for each material. The sample should be handled with tweezers. Do not
Touch the sample directly with your hands to avoid contamination (grease, salt). Be very careful when using gloves because of the contamination caused by the separation on the gloves
Infection may lead to errors in quality determination. If repeated tests are inconsistent, the temperature and humidity of the weighing environment should be recorded.
8.2 Weighing before the test
8.2.1 The sample holder should be baked at 1000°C for at least 24 hours before use to remove volatile chemicals from the production process. If already
The used sample holder may absorb water and should be dried above 100℃.
8.2.2 The sample mass [mT(t0)] should be measured before exposure, see Figure 5.Each sample should be tested at least twice, the accuracy should not be less than 0.02mg.
The maximum difference between each measurement result should not exceed 0.05 mg.
8.2.3 The mass of the sample holder [mS(t0)] should be measured before exposure, see Figure 5.Each sample holder should be tested at least twice. When the sample holder
When the mass is less than 20g, the accuracy should not be less than 0.02mg, and the maximum difference between each measurement result should not exceed ±0.05mg. When the sample is supported
When the mass of the rack is greater than or equal to 20g, the accuracy should not be less than 0.1mg, and the maximum difference between each measurement result should not exceed ±0.3mg. when
When only the data of the change in the net mass of the sample is required, the mass of the sample holder may not be measured.
Explanation.
mST---The quality of the sample holder and sample;
mS ---The quality of the sample holder;
mT --- The quality of the sample.
Figure 5 Quality determination type Ⅰ
8.3 Determination of intermediate state quality change (discontinuous isothermal test only) and final quality change
8.3.1 After removing the sample holder (including the sample) from the heating furnace, it should be placed in the weighing room for 15 minutes to adapt to the environment. The sample should not be removed
Oxide scale, but it is allowed to gently pat the sample inside the bracket to remove the loose scale attached to the sample and ensure that the scale is peeled off
Can also be collected. When re-inserted in the heating furnace for subsequent tests, all peeled scale should be retained in the sample holder.
8.3.2 If water-absorbent corrosion products are formed, they should be weighed as soon as possible after taking out the sample from the heating furnace, or placed in a desiccator before weighing.
8.3.3 If a large amount of volatile substances are generated, the weighing will be affected. The appearance of volatile substances is formed in the lower temperature part of the heating furnace
Into liquid or solid matter.
8.3.4 When determining the quality change in each state and final state in the middle, the quality of the sample holder, including the sample and the exfoliated scale,
The quality of the sample holder containing the peeled scale and the sample (including the closely attached scale) should be measured, see Figure 7.Every measurement should be measured
2 times, the accuracy of each measurement should be no less than 0.02mg, and the standard deviation of each group of measurement results should not be greater than 0.05mg.
8.3.5 When weighing, care should be taken to prevent the scale from peeling due to mechanical contact with tweezers. Test of the rod support design shown in Figure 4
The sample holder can solve this problem, and it can realize that the tweezers are not in direct contact with the sample when determining the weight change (see Figures 6 and 7).
The total mass change Δmg is calculated according to equation (1).
Δmg(tn)=mST(tn)-mST(t0) (1)
In the formula.
Δmg(tn)---the total change in mass of tn at the time point, the unit is milligram (mg);
mST(tn)---The mass of the sample holder and sample at the time point tn, the unit is milligram (mg);
mST(t0)---The initial mass of the specimen holder and specimen before the specimen, in milligrams (mg).
The mass Δmsm of the exfoliated scale is calculated according to formula (2).
Δmsm(tn)=mS(tn)-mS(t0) (2)
In the formula.
Δmsm(tn)---The mass change of peeled scale at time tn, the unit is milligram (mg);
mS(tn) ---The mass of the sample holder at the time point tn, in milligrams (mg);
mS(t0) ---The initial mass of the sample holder before the sample, in milligrams (mg).
The sample mass change Δmn is calculated according to formula (3). When the rod-supported design shown in Figure 6 is used, the sample mass change Δmn is
Formula (4) calculation.
Δmn(tn)=mT(tn)-mT(t0) (3)
In the formula.
Δmn(tn)---the mass change of the sample at time tn, the unit is milligram (mg);
mT(tn)---The mass of the sample at time tn, in milligrams (mg);
mT(t0)---The initial mass of the sample before the sample, the unit is milligram (mg).
Δmn(tn)=Δmg(tn)-Δmsm(tn) (4)
In the formula.
Δmn(tn)---the mass change of the sample at time tn, the unit is milligram (mg);
Δmg(tn)---the total change in mass of tn at the time point, the unit is milligram (mg);
Δmsm(tn)---The mass change of peeled scale at time tn, the unit is milligram (mg).
Explanation.
mST---The quality of the sample holder and the sample with alumina rods;
mS ---The quality of the sample holder;
mT ---The quality of the sample with rod.
Note. The sample can be taken out by gripping the rod with tweezers.
Figure 6 Quality determination type Ⅱ
Explanation.
1 --- exfoliated oxide;
mST(ti)---The quality of the sample holder and the sample with alumina and other rods at the time of ti;
mS(ti)---The quality of the ti sample holder at the time point;
mT(ti)---The quality of the sample with rod at the time ti.
Figure 7 Quality determination type Ⅱ (wh...
...
