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Nitriding treatment process, types, and applicable boundaries of die-casting molds

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  • Release time: 2026-11-07

Nitriding treatment process, types, and applicable boundaries of die-casting molds
Nitriding is the mainstream process for die casting mold surface strengthening, and many purchasers confuse nitriding with coatings. Xinfeng Machinery compares ion nitriding and gas nitriding to clarify the benefits and limitations.
1、 Principle and Hardness Performance of Nitriding Reinforced Bottom Layer
Nitriding is the infiltration of nitrogen elements into the surface of the substrate to form a nitride hardened layer, not a coating. After nitriding, the surface hardness of H13 mold can reach HV950-1200, improving its ability to resist biting, wear, and aluminum adhesion. The hardened layer is usually 0.08-0.15mm, and the matrix still maintains its original toughness, resisting thermal shock cracking. Alloy wheel mold cavities often use nitride as the base layer, followed by an AlTiN coating to form a composite protection.
2、 Differences in selection between gas nitriding and ion nitriding
Gas nitriding has lower costs and is suitable for batch production and simple cavity design; Disadvantages: Poor uniformity of nitride layer, thick white layer, high brittleness of white layer, and easy peeling under thermal shock. Ion nitriding (glow nitriding) has controllable temperature, thin white layer, minimal deformation, and is preferred for patterned and mirrored wheel hub cavities. The quotation is about 30% higher than gas nitriding. The nitriding temperature should be controlled at 480-520 ℃. If the temperature is too high, tempering will reduce the hardness of the substrate.
3、 Suitable and unsuitable working conditions for nitriding
Suitable for: frequent adhesion of aluminum, ejector pins, slider sealing surfaces, and long-term two shift mass production molds; Suitable as a pre-treatment before coating to enhance coating adhesion. Nitriding cannot solve the problem of thermal fatigue cracks, and deep cracks in the substrate defects will still propagate outward after nitriding. It is not recommended to nitride molds that already have obvious cracks, as nitriding will make the cracks easier to propagate.
4、 The combination logic of nitride and PVD coatings
Nitriding is a substrate modification that strengthens from the inside out; PVD coating is a surface coating. Standard combination: Nitriding base+Polishing+AlTiN coating, dual enhancement of wear resistance and anti stick aluminum. Only for nitriding with a high temperature resistance limit lower than AlTiN coating, continuous high-temperature die-casting, the nitriding surface will still oxidize and stick to aluminum. Low pressure casting molds have low aluminum adhesion load, and many only require nitriding without the need for additional coating.
5、 Dimensional changes and processing precautions after nitriding
Nitriding will cause slight expansion, usually 0.005-0.015mm, and the precision mold cavity must reserve expansion allowance in advance. After nitriding, it cannot be polished extensively as polishing will directly remove the hardened layer. The application of metal injection mold nitriding is relatively rare, and DLC coating is more commonly used directly. Google's "nesting for die casting mold" is a high-frequency search term for overseas process engineers.
FAQ
Can it still be polished after nitriding?
Light polishing can remove the surface white layer, but cannot cut in large quantities.
Do we need to remove the nitride white layer?
The thick white layer has high brittleness and is easily peeled off by thermal shock. Mirror molds usually remove the white layer.
How many times can nitriding be done?
Generally, after 1-2 cycles of nitriding and cumulative tempering, the hardness of the substrate continues to decrease.
4. Which has a more significant lifespan improvement, nitriding or coating?
AlTiN coating is better under high temperature continuous working conditions; The slider and ejector pin are prioritized for anti bite nitriding.
5. Do low-pressure wheel hub molds need nitriding?
Nitriding is recommended for the flushing area of the gate, and the main cavity should be selected as needed.
6. Is the nitriding deformation significant?
Ionic nitriding has minimal deformation, while gas nitriding carries a higher risk of deformation.
7. Does the mold need to undergo proper heat treatment before nitriding?
Quenching and tempering must be completed to completely release internal stress, otherwise deformation will occur after nitriding.
Can nitriding repair aluminum adhesion?
Nitriding reduces the probability of aluminum adhesion, but stubborn aluminum adhesion has already formed and needs to be polished and cleaned first.

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