GB/T 14999.2-2025 Test methods for superalloys—Part 2：Microstructure English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS 77.140.99 CCS H57
People's Republic of China National Standard
GB/T 14999.2-2025
Replacing GB/T 14999.4-2012, GB/T 14999.6-2010
Test Methods for Superalloys-Part 2: Microstructure
Issued on August 29, 2025
Implemented on March 1, 2026
Issued by
State Administration for Market Regulation
Standardization Administration of China
Contents
Foreword
Introduction
1 Scope
2 Normative References
3 Terms and Definitions
4 Sampling and Preparation
5 Determination and Result Presentation
6 Inspection Report
Test Methods for Superalloys-Part 2: Microstructure
1 Scope
This document specifies the sampling and preparation, determination and result presentation, inspection report, etc., for the microstructure examination of wrought superalloys. It is applicable to the detection and evaluation of grain structure and primary carbides in rolled and forged wrought superalloy products. Other superalloys may reference this document for use.
2 Normative References
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the document (including any amendments) applies.
GB/T 6394 Methods for Average Grain Size Measurement
GB/T 24177 Characterization and Measurement of Dual Grain Size
GB/T 30067 Metallographic Terms
YB/T 4290 Determination of Maximum Grain Size Grade (ALA Grain Size) on Metallographic Test Surfaces
3 Terms and Definitions
The terms and definitions given in GB/T 6394 and GB/T 30067, and the following terms and definitions, apply to this document.
3.1 Uniform Grain Structure
A grain structure where the grain area, diameter, or intercept length exhibits a single-peak distribution, which approximates a log-normal distribution.
3.2 Duplex Grain
A grain structure where at least two distinctly different grain sizes and distribution patterns exist, with a grain size difference of no less than 3 levels between fine and coarse grains.
3.3 Banding Grain
Grains distributed along the metal flow direction or the processing direction, with a grain size difference of no less than 3 levels between alternating regions.
3.4 Individual Coarse Grain (ALA Grain)
The largest grain observed in randomly dispersed isolated coarse grains, where the grain size difference between the coarse grain and the matrix is no less than 3 levels, and the area percentage of the coarse grain does not exceed 5% of the total observed area.
Note: If the area percentage of coarse grains exceeds 5%, the provisions for bimodal grains (3.7) in this document shall apply.
3.5 Wide-Range Grain
Grains with a wide range of sizes randomly distributed in the field of view, where the grain size difference between the largest and smallest grains is no less than 5 levels.
3.6 Necklace Grain
A grain structure where two grain sizes with a difference of no less than 3 levels are distributed in the field of view, with small grains surrounding large grains, and the area percentage of small grains not exceeding 50% of the total observed area.
Note: If the area percentage of small grains exceeds 50%, the provisions for bimodal grains (3.7) in this document shall apply.
3.7 Bimodal Grain
A grain structure where two distinctly different grain sizes are randomly distributed in the field of view, with a grain size difference exceeding 4 levels between the two grain sizes, each grain size accounting for more than 5% of the total area, and the sum of the area percentages of the two grain sizes exceeding 75% of the total observed area.
3.8 Cross-Section Surface Coarse Grain
A grain structure where the surface layer consists of coarse grains and the center consists of fine grains, with a grain size difference of no less than 3 levels between the two regions.
Note: A coarse grain transition zone is commonly observed in the fine grain zone near the surface layer coarse grain area.
4 Sampling and Preparation
4.1 Sampling
4.1.1 For rolled products, the sampling direction, location, number of samples, and number of fields of view for determination shall be carried out in accordance with the provisions of the product standard, relevant technical conditions, and contract. If not specified, sampling shall generally be performed parallel to the longitudinal direction (rolling direction). When the sample diameter or side length does not exceed 32 mm, half of the sample shall be cut along the longitudinal direction, with the centerline of the test surface passing through the axis center (deviation ±0.5 mm). When the sample diameter or side length exceeds 32 mm, a quarter of the sample shall be cut along the longitudinal direction, with the test surface passing through the axial centerline (deviation ±0.5 mm).
4.1.2 For forged products, the sampling direction, location, number of samples, and number of fields of view for determination shall be carried out in accordance with the provisions of the product standard, relevant technical conditions, and contract. If not specified, sampling shall generally be performed along the longitudinal direction (radial-axial direction) of the product. For forged discs (rings), samples shall be cut from the radial-axial center and 1/2R positions of the forged component, with the test surface being the radial-axial surface.
4.1.3 When cutting samples, methods that do not alter the alloy microstructure shall be used. The test surface shall be free from the effects of processing methods (e.g., cutting heat, press wrinkles from punching or sawing, hammering, etc.). Sampling from products with surface quality or dimensional non-conformities is allowed.
4.1.4 The recommended sample thickness for bars is 10–15 mm, and for plates, 20 mm × 30 mm.
4.2 Preparation
4.2.1 After final heat treatment, samples for grain size determination shall be mounted (if necessary), ground, polished, and etched in accordance with GB/T 13298, ensuring that all grain boundaries are clearly visible. Samples shall not undergo repeated heat treatment.
4.2.2 Samples for primary carbide distribution determination shall be prepared by grinding and polishing. Samples generally shall not be etched.
4.2.3 If the duplex grain structure and primary carbide distribution in the product vary significantly, macroscopic etched samples shall be prepared and examined first, followed by microscopic examination and determination of the areas of interest as needed.
4.2.4 If not specified in the product standard or technical agreement, the recommended polishing and etching methods are provided in Tables 1 and 2. Other product sample etching methods may reference these methods.
Standard
GB/T 14999.2-2025 Test methods for superalloys—Part 2：Microstructure (English Version)
Standard No.
GB/T 14999.2-2025
Status
to be valid
Language
English
File Format
PDF
Word Count
14500 words
Price(USD)
435.0
Implemented on
2026-3-1
Delivery
via email in 1~5 business day
Detail of GB/T 14999.2-2025
Standard No.
GB/T 14999.2-2025
English Name
Test methods for superalloys—Part 2：Microstructure
GB/T 14999.2-2025 Test methods for superalloys—Part 2：Microstructure English, Anglais, Englisch, Inglés, えいご
This is a draft translation for reference among interesting stakeholders. The finalized translation (passing through draft translation, self-check, revision and verification) will be delivered upon being ordered.
ICS 77.140.99 CCS H57
People's Republic of China National Standard
GB/T 14999.2-2025
Replacing GB/T 14999.4-2012, GB/T 14999.6-2010
Test Methods for Superalloys-Part 2: Microstructure
Issued on August 29, 2025
Implemented on March 1, 2026
Issued by
State Administration for Market Regulation
Standardization Administration of China
Contents
Foreword
Introduction
1 Scope
2 Normative References
3 Terms and Definitions
4 Sampling and Preparation
5 Determination and Result Presentation
6 Inspection Report
Test Methods for Superalloys-Part 2: Microstructure
1 Scope
This document specifies the sampling and preparation, determination and result presentation, inspection report, etc., for the microstructure examination of wrought superalloys. It is applicable to the detection and evaluation of grain structure and primary carbides in rolled and forged wrought superalloy products. Other superalloys may reference this document for use.
2 Normative References
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the document (including any amendments) applies.
GB/T 6394 Methods for Average Grain Size Measurement
GB/T 24177 Characterization and Measurement of Dual Grain Size
GB/T 30067 Metallographic Terms
YB/T 4290 Determination of Maximum Grain Size Grade (ALA Grain Size) on Metallographic Test Surfaces
3 Terms and Definitions
The terms and definitions given in GB/T 6394 and GB/T 30067, and the following terms and definitions, apply to this document.
3.1 Uniform Grain Structure
A grain structure where the grain area, diameter, or intercept length exhibits a single-peak distribution, which approximates a log-normal distribution.
3.2 Duplex Grain
A grain structure where at least two distinctly different grain sizes and distribution patterns exist, with a grain size difference of no less than 3 levels between fine and coarse grains.
3.3 Banding Grain
Grains distributed along the metal flow direction or the processing direction, with a grain size difference of no less than 3 levels between alternating regions.
3.4 Individual Coarse Grain (ALA Grain)
The largest grain observed in randomly dispersed isolated coarse grains, where the grain size difference between the coarse grain and the matrix is no less than 3 levels, and the area percentage of the coarse grain does not exceed 5% of the total observed area.
Note: If the area percentage of coarse grains exceeds 5%, the provisions for bimodal grains (3.7) in this document shall apply.
3.5 Wide-Range Grain
Grains with a wide range of sizes randomly distributed in the field of view, where the grain size difference between the largest and smallest grains is no less than 5 levels.
3.6 Necklace Grain
A grain structure where two grain sizes with a difference of no less than 3 levels are distributed in the field of view, with small grains surrounding large grains, and the area percentage of small grains not exceeding 50% of the total observed area.
Note: If the area percentage of small grains exceeds 50%, the provisions for bimodal grains (3.7) in this document shall apply.
3.7 Bimodal Grain
A grain structure where two distinctly different grain sizes are randomly distributed in the field of view, with a grain size difference exceeding 4 levels between the two grain sizes, each grain size accounting for more than 5% of the total area, and the sum of the area percentages of the two grain sizes exceeding 75% of the total observed area.
3.8 Cross-Section Surface Coarse Grain
A grain structure where the surface layer consists of coarse grains and the center consists of fine grains, with a grain size difference of no less than 3 levels between the two regions.
Note: A coarse grain transition zone is commonly observed in the fine grain zone near the surface layer coarse grain area.
4 Sampling and Preparation
4.1 Sampling
4.1.1 For rolled products, the sampling direction, location, number of samples, and number of fields of view for determination shall be carried out in accordance with the provisions of the product standard, relevant technical conditions, and contract. If not specified, sampling shall generally be performed parallel to the longitudinal direction (rolling direction). When the sample diameter or side length does not exceed 32 mm, half of the sample shall be cut along the longitudinal direction, with the centerline of the test surface passing through the axis center (deviation ±0.5 mm). When the sample diameter or side length exceeds 32 mm, a quarter of the sample shall be cut along the longitudinal direction, with the test surface passing through the axial centerline (deviation ±0.5 mm).
4.1.2 For forged products, the sampling direction, location, number of samples, and number of fields of view for determination shall be carried out in accordance with the provisions of the product standard, relevant technical conditions, and contract. If not specified, sampling shall generally be performed along the longitudinal direction (radial-axial direction) of the product. For forged discs (rings), samples shall be cut from the radial-axial center and 1/2R positions of the forged component, with the test surface being the radial-axial surface.
4.1.3 When cutting samples, methods that do not alter the alloy microstructure shall be used. The test surface shall be free from the effects of processing methods (e.g., cutting heat, press wrinkles from punching or sawing, hammering, etc.). Sampling from products with surface quality or dimensional non-conformities is allowed.
4.1.4 The recommended sample thickness for bars is 10–15 mm, and for plates, 20 mm × 30 mm.
4.2 Preparation
4.2.1 After final heat treatment, samples for grain size determination shall be mounted (if necessary), ground, polished, and etched in accordance with GB/T 13298, ensuring that all grain boundaries are clearly visible. Samples shall not undergo repeated heat treatment.
4.2.2 Samples for primary carbide distribution determination shall be prepared by grinding and polishing. Samples generally shall not be etched.
4.2.3 If the duplex grain structure and primary carbide distribution in the product vary significantly, macroscopic etched samples shall be prepared and examined first, followed by microscopic examination and determination of the areas of interest as needed.
4.2.4 If not specified in the product standard or technical agreement, the recommended polishing and etching methods are provided in Tables 1 and 2. Other product sample etching methods may reference these methods.
