This standard specifies the method for determining the depth of nitriding layer on the surface of steel parts and the evaluation level of metallographic structure before and after nitriding. This standard is applicable to the determination and evaluation of the depth of nitriding layer, brittleness, looseness, and vein nitrides on the surface of steel parts after gas nitriding, ion nitriding, and nitrocarburizing (soft nitriding). GB/T 11354-1989 Determination of nitriding layer depth and metallographic structure inspection of steel parts GB/T11354-1989 Standard download decompression password: www.bzxz.net

UDC 621.8 :669.14:620.18
National Standard of the People's Republic of China
GB 1135 4 - 89
Steel -iron parts-Determination of nitrided case depthand metallographic examination of nitriding structurePublished on May 6, 1989
Implemented on January 1, 1990
State Administration of Technical Supervision
National Standard of the People's Republic of China
Steel -iron parts--Determination of nitrided case depthand metallographic examination of nitriding structure strgclere1Subject content and scope of application
GB 1125 4— 89
This standard specifies the method for determining the depth of nitriding layer on the surface of steel parts and the evaluation level of metallographic structure before and after nitriding. This standard is applicable to the determination and evaluation of the depth of nitriding layer on the surface of steel parts after gas nitriding, ion nitriding, and nitrogen-carbon co-nitriding (soft nitriding). 2Referenced standards
GB 9450Determination and verification of effective hardening depth of steel GE 9451
Determination of total hardening layer depth or effective hardening layer depth on thin surface of steel parts3Terms
3.1Original structure refers to the metallographic structure of the following parts before rubbing treatment. 3.2. Depth of nitriding layer: The nitriding layer includes the compound layer (self-brightening layer) and the diffusion layer. Its depth refers to the vertical distance measured from the surface of the workpiece to the boundary hardness value specified at the place where there is a clear boundary with the matrix structure (indicated by the Latin letter DN). 3.3 Brittleness of nitriding layer: refers to the degree of fragmentation of the Vickers hardness mark corners on the surface of the nitrided part under a certain test force. 3. Looseness of nitriding layer: refers to the density of micropores in the compound layer on the surface of the nitrided part. 3.5 Vein: refers to the wavy nitrides in the diffusion layer of the nitrided part that run parallel to the surface. Inspection of original organization
4.1 The original organization level before nitriding is divided into 5 levels according to the number of free ferrite in tempered troostite, see Figures 1 to 5 and Table 1. 4.2 The original organization should be inspected before nitriding (for large parts, it can be inspected within the range of 2mm depth from the surface under a microscope and magnified 500 times, and evaluated with reference to the original organization level chart. General parts with levels 1 to 3 are qualified, and important parts with levels 1 to 2 are qualified. 4.3 The working surface of nitrided parts is not allowed to have decarburized layer or coarse tempered troostite structure. Table!
Description of the original organization level before nitriding
Uniform fine needle-shaped troostite, free ferrite with very little uniform fine needle-shaped troostite, free ferrite with blood core 5 % Needle-shaped tempered ferrite, free ferrite salt <15% Fine needle-shaped tempered ferrite, free high ferrite content 2-way ferrite (normalizing) + free ferrite film> 25% State Administration of Technical Supervision 19~05-06 Approved
19:90-01-01 Implementation
GB 11354-89
Original organization level before nitriding
4% ethanol solution etch × 500
Figure】Level
Figure 22Level
Figure 3Level
5 Sample conditions
G 6 1135 4-89
Figure 44 level
Figure 55 level
5.1 The sample should be cut from the nitrided part. It can also be a sample with the same material, processing conditions and processing accuracy as the part and nitrided in the same furnace.
5.2 The inspection position should be representative. The sample should be cut vertically on the surface of the nitrided layer. During the grinding and polishing process, the inspection surface is not allowed to overheat, and the edges are not allowed to be chamfered or peeled off.
5. For the sample with brittle nitrided layer, the surface loss should be >R0.25～0.63um. It is not allowed to grind away the compound layer. Determination method of nitriding layer depth
6.1 Hardness method
This standard adopts Vickers hardness, and the test force is specified as 2.94N (0.3kgf). The vertical distance from the surface of the sample to the point 50HV higher than the Vickers hardness value of the matrix is ​​the nitriding layer depth. The hardness value measured at a distance of about 3 times the nitriding depth (at least 3 points are averaged) is taken as the measured matrix hardness value. For steel parts with very slow changes in the hardness of the nitriding layer (such as carbon steel or low-phosphorus low-alloy steel parts), the nitriding layer depth can be measured from the sample surface in the vertical direction to a point 30HV higher than the Vickers hardness value of the matrix. GB 1135 4--- B9
When the depth of the nitrided layer is not suitable for the size of the long scar, the parties concerned may negotiate and use a test force within the range of 1.96N (0.2kgf) ~ 19.6N (2kgf), but it must be noted after HV: such as HV0.2, indicating a test force of 1.96N (0.2kgf). The depth of the nitrided layer is indicated by the letter DN, in millimeters, with two decimal places. For example, 0.25DN300HV0.5, indicating that the limit hardness value is 300V, the test force is 4.903N (0.5kgf), the nitriding depth is 0.25mm, 6.2 The measurement steps and results are indicated in accordance with GB9450 and GB9451 standards. 6.3 Metallographic methodbzxZ.net
Measure the sample under a microscope with a magnification of 10 or 200 times according to the method shown in Figures 6 to 10. The distance from the sample surface to the obvious boundary with the matrix structure in the vertical direction is the depth of the penetration layer. 6.4 Arbitration
When there is protection, the basic measurement method is used as the piece judgment method. Ammonia layer depth measurement diagram
Depth
638CrM0A1 steel body nitriding 4% nitric acid ethanol drop solution corrosion × 100Figure 740℃ nitriding selenoic acid alcohol solution slow corrosion × 100Xian Medical Insurance Store
GB1185A—89
Figure 8HT250 gray cast iron nitrogen carburizing
selenoic acid alcohol solution corrosion × 200
38CrMoA1 steel body post-heating to 800 insulation 1.5min/mmClean fire Figure 9
4 Nitric acid alcohol solution corrosion × 10
After the degree
Figure 102U magnetic rinse nitrogen carburizing after 300℃ tempering 1h4% nitric acid alcohol solution corrosion × 2004
7 Ammonia brittleness test
GB 11 35 4- 89
1.1 Brittleness level of nitriding layer The degree of edge and corner fragmentation of Vickers hardness indentation is divided into 5 levels, see Figure 11 and Table 2. 7.2 To test the brittleness of nitriding layer, the Vickers hardness ratio is used. The test force is specified to be 98.07N (ikgf). The loading must be slow (completed within 5~9s), and the loading must be stopped for 5~10s before unloading. If there are special circumstances, after consultation between the relevant parties, a test force of 49.03N (5kgh) or 294.21N (30kgf) can also be used. The parts must be converted according to the values ​​in Table 3.
1.3 The Vickers hardness mark is tested under 100 times magnification (refer to Figure 11 for evaluation level). At least three points are measured for each piece, among which: the points are at the same level, and the grade can be determined. Otherwise, the measurement is repeated once. 7.4 The brittleness of the nitrided layer should be tested on the working part of the part or on the surface of the furnace sample. General parts are qualified for 1 to 3 levels, and important parts are qualified for 1 to 2 levels. For parts with grinding residues after nitriding, it can also be measured on the surface after grinding away the machining residues. 7.5 Parts that have been gas nitrided must be tested for brittleness. Nitrided layer brittleness level chart
98.07N (10kgf) test × 100
test N (kgf)
244-2 (30)
8 Nitrided layer looseness test
GB 11354--89
Description of the level of nitriding layer
The edge of the mark is complete
E wolf--edge or--crack
Wolf edge is--angle crack
Yu Ning three sides are strictly angle crack
Medical mark four sides or four phases are even
Tool.1 The looseness level of the nitriding layer is divided into 5 levels according to the shape, number and density of the micropores in the surface compound layer, see Figure 12 to Figure 16 and Table 48.2 The looseness of the nitriding layer is tested under a microscope with a magnification of 500 ℃. The most severely loosened part is selected and evaluated with reference to the looseness level chart of the nitriding layer. General parts with levels 1 to 3 are qualified, and important parts with levels [~2 are qualified. 8.3 Parts treated by nitrocarburizing must be subjected to looseness inspection. Looseness level of ammonia-carburized layer
2% nitric acid ethanol solution etch ×506
GB 354-89
Figure 132 level
Figure 113 level
Figure 15 level
CB 11354-89
Figure 165 Level
Repair level description
Compound layer is dense, with a few micropores on the surface. The compound layer has dense nests or dot-shaped pores, and the concentration of micropores decreases from the surface to the inside. The micropores are concentrated. The compound layer is more than 3/4 thick, and some are densely distributed. 9 Inspection of nitrides in the diffusion layer
9.1 The nitride level of the nitriding layer is divided into 5 levels according to the morphology, number and distribution of nitrides in the diffusion layer, as shown in Figures 17 to 21 and Table 5. 9.2 The diffusion layer is magnified 50 times under a microscope for inspection, and the worst part is selected for evaluation with reference to the nitride level of the nitriding layer - general parts are qualified for 1 to 3, and heavy parts are qualified for 1 to 2.
9.3 Parts that have been gas nitrided or ion nitrided must be inspected for nitrides. EN171 level
CB 11354-89
Figure 182 level
Figure 193 level
Inspection report
G611354-89
Figure 215 level
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The inspection report should include the following contents:
Part number, part name, material and Germany: point 8
Part inspection part or sample and guide and inspection number: inspection method:
Inspection results
Inspection date and inspector's signature.
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