Nitriding Treatment Parameters for Extending Automotive Mold Service Life

Nitriding treatment is the mainstream surface strengthening process for automotive aluminum alloy casting molds, which can significantly improve mold surface hardness, high-temperature wear resistance and thermal fatigue resistance, and is the key process to extend mold service life. Automotive molds represented by wheel and engine casting molds have strict requirements for nitriding parameters, and non-standard parameters will lead to insufficient hardening, local brittleness or stress cracks. Industry optimal process parameters take 520-540℃ constant temperature nitriding as the core, among which 530℃ is the most balanced temperature, which can make the mold surface form dense nitride structure without damaging the internal toughness of mold steel. The treatment time is controlled at 18-22 hours, and 20 hours is the best parameter for mass production, which can form a 0.3-0.5mm thick uniform hardened layer, meeting the long-term mass casting demand. Nitrogen flow rate is stably controlled at 0.8-1.2m³/h to ensure uniform nitrogen atom coverage on the mold cavity surface and avoid local treatment dead zones. After nitriding, low-temperature tempering at 180℃ for 2 hours is required to eliminate residual thermal stress and prevent delayed crack failure during mold use. After standardized nitriding treatment, the surface hardness of automotive molds can be stably maintained at 1100-1200HV, the high-temperature wear resistance is improved by 58%, and the comprehensive service life is extended by 45% compared with untreated molds.