GB/T 11354-2025Determination of nitriding hardness depth and metallographic examination for steel (English PDF)

1 Scope

GB/T 11354-2025 is the Chinese national standard on determination of nitriding hardness depth and metallographic examination for steel, in the field of manufacturing engineering. The /T suffix marks it as a recommended standard: it is not compulsory by itself, but it becomes binding as soon as a contract, a tender or a customer specification calls it up - which in practice is how most foreign buyers meet it. It was issued on 29 August 2025 by the State Administration for Market Regulation; Standardization Administration of China, and has been in force since 1 March 2026. Classification: ICS 25.200, CCS J36. This page is published from the official record of the standard held by the Chinese standards administration: the identification, the dates, the classification and the issuing body are taken from there. The clause text, the tables and the numeric limits are in the document itself, which is delivered complete in English translation.

This Document specifies the method for determining the depth of the nitrided and nitrocarburized layers on steel parts and the examination of the metallographic structure before and after nitriding. This Document applies to the determination of the nitriding hardened depth and the compound layer thickness after gas nitriding, ion nitriding, and nitrocarburizing treatments on steel parts, as well as the examination and evaluation of nitrided layer's brittleness, porosity, nervation and wave like nitride, and the microstructure before nitriding.

2 Normative References

The provisions in following documents become the essential provisions of this Document through reference in this Document. For the dated documents, only the versions with the dates indicated are applicable to this Document; for the undated documents, only the latest version (including all the amendments) is applicable to this Document.

GB/T 4340.1 Metallic materials - Vickers hardness test - Part

3 Terms and Definitions

For the purposes of this Document, the terms and definitions given in GB/T 7232 and the following apply.

3.1 Nitriding hardness depth; NHD The vertical distance from the surface of the nitrided layer to the point where is 50 HV hardness limit higher than the core. NOTE. The core hardness is the arithmetic mean of 5 or more measurements at 3 times the hardened layer depth, rounded-off to the nearest multiple of 10 HV.

3.2 Compound layer thickness; CLT The thickness of the surface compound layer formed by the infiltrating elements and the metal elements in the matrix during chemical heat treatment.

3.3 Prior metallographic structure; original structure Microstructure of steel before nitriding treatment.

3.4 Brittleness of nitrided layer The degree of chipping of the corners of the Vickers hardness indentation on the surface of the nitrided part under a certain test force.

3.5 Porosity of nitrided layer The density of micropores in the compound layer on the surface of nitrided parts.

3.6 Nervation and wave like nitride The pulse-like nitrides in the diffusion layer of the nitrided part are parallel to the surface.

4 Symbols and Abbreviated Terms

Table 1 gives the symbols and abbreviated terms that are applicable to this Document.

5 Determination of Nitriding Hardness Depth...