GB/T 11354-2025 Determination of nitriding hardness depth and metallographic examination for steel English, Anglais, Englisch, Inglés, えいご
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ICS 25.200 CCS J 36
NATIONAL STANDARD OF THE PEOPLE'S REPUBLIC OF CHINA
GB/T 11354-2025
Replaces GB/T 11354-2005
Determination of nitriding hardness depth and metallographic examination for steel
Issued on 2025-08-29 | Implemented on 2026-03-01
Issued by
State Administration for Market Regulation
Standardization Administration of China
Contents
Foreword
1 Scope
2 Normative references
3 Terms and definitions
4 Symbols and abbreviated terms
5 Determination of nitriding layer depth
6 Metallographic examination of nitrided layer
7 Test report
Appendix A (Normative) Determination of nitriding hardness depth using interpolation method
References
Determination of nitriding hardness depth and metallographic examination for steel
1 Scope
This document specifies the methods for determining the depth of nitrided layers and nitrogen-carbon co-diffusion layers in steel parts, and the methods for the metallographic examination of the microstructure before and after nitriding.
This document applies to the determination of nitriding hardness depth and compound layer thickness of steel parts after gas nitriding, ion nitriding, or nitrogen-carbon co-diffusion treatment, as well as the examination and assessment of nitrided layer brittleness, porosity, veined nitride, and pre-nitriding microstructure.
2 Normative references
The following documents contain provisions which, through reference in this text, constitute provisions of this document. For dated references, only the editions cited apply. For undated references, the latest edition (including any amendments) applies.
GB/T 4340.1 Metallic materials—Vickers hardness test—Part 1: Test method
GB/T 4340.2 Metallic materials—Vickers hardness test—Part 2: Verification and calibration of testing machines
GB/T 7232 Metal heat treatment—Vocabulary
GB/T 18449.1 Metallic materials—Knoop hardness test—Part 1: Test method
GB/T 18449.2 Metallic materials—Knoop hardness test—Part 2: Verification and calibration of testing machines
GB/T 34895 General rules for metallographic examination of heat treatment
3 Terms and definitions
The terms and definitions defined in GB/T 7232, and the following terms and definitions apply to this document.
3.1 nitriding hardness depth (NHD)
The perpendicular distance from the surface of the nitrided layer to the point where the hardness exceeds the core hardness by 50 HV.
Note: The core hardness is the arithmetic average of more than five measurement values at a location three times the hardened layer depth. The value shall be rounded to the nearest multiple of 10 HV.
3.2 compound layer thickness (CLT)
The thickness of the surface compound layer formed by the diffused elements and the base metal elements during chemical heat treatment.
3.3 prior metallographic structure (original structure)
The microstructure of the steel part before nitriding treatment.
3.4 brittleness of nitrided layer
The degree of corner breakage of the Vickers hardness indentation on the surface of the nitrided part under a specific test force.
3.5 porosity of nitrided layer
The density of micropores within the compound layer on the surface of the nitrided part.
3.6 nervation and wavelike nitride
The veined and wavelike nitrides that run parallel to the surface within the diffusion layer of the nitrided part.
4 Symbols and abbreviated terms
The symbols and abbreviated terms listed in Table 1 are applicable to this document.
Table 1 Symbols and abbreviated terms
