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Metallographic examination of uniformity of nitriding layer thickness in multiple parts of gears
2026-06-11
Gears are key components of transmission, which are subjected to alternating stress and impact loads for a long time, and their tooth surfaces are prone to wear, pitting, and peeling. Gas nitriding can form a high hardness nitride layer on the tooth surface, improving wear resistance and fatigue resistance. Uneven thickness of nitride layer can cause local failure and brittle fracture, affecting the service life of gears. This time, multiple parts of the gear were subjected to metallographic testing to measure the thickness of the nitride layer and verify the uniformity and process stability of the nitride layer.
detection method
Cut samples at four different positions on the gear, and after embedding, grinding, polishing, and corrosion, observe and measure the thickness of the nitride layer using a metallographic microscope.
In the metallographic photo, the dark color above is the inlay material, the bright white layer in the middle is the nitride layer, and the structure of the gear substrate steel is below.
Test results
Position 1:10.06 μ m
Position 2: 10.06 μ m
Position 3: 9.27 μ m
Position 4: 9.75 μ m
All samples have a continuous and smooth nitride layer, without defects such as holes, cracks, peeling, etc., and the matrix structure is in normal condition.
Uniformity analysis
The thickness range of the nitride layer is 9.27~10.06 μ m, with a maximum thickness difference of only 0.79 μ m, and the overall thickness fluctuation is very small; The layer thickness at two locations is exactly the same, indicating stable temperature and atmosphere distribution inside the furnace. The slight difference in thickness comes from conventional factors such as workpiece structure, surface cleanliness, and subtle temperature differences inside the furnace.
Conclusions and Recommendations
Conclusion: The uniformity of the gear nitriding layer is good, and the current nitriding process is stable and qualified;
Suggestion: Unify the pre-treatment cleaning and roughness of workpieces, optimize clamping to avoid tooth surface obstruction, which can further reduce thickness deviation.
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