Stainless Steel – AISI 420 (Fe86.7/Cr13.0/C0.3) is a martensitic stainless steel known for its high hardness, wear resistance, and moderate corrosion resistance. With a typical composition of approximately 13% chromium and 0.3% carbon, it offers a balance between mechanical strength and corrosion performance, making it a popular material in engineering, tooling, and medical applications. The material’s microstructure can be tailored through controlled heat treatments, providing flexibility for various industrial uses.
Material Overview
Physically, AISI 420 exhibits high hardness levels—up to 50–55 HRC when hardened—making it one of the hardest commonly used stainless steels. This hardness can be further enhanced through surface modification techniques such as plasma oxy-nitriding, which increases surface wear resistance and hardness without introducing structural defects (Kim & Lee, 2023). The martensitic microstructure, derived from heat treatment, provides strength and dimensional stability, while the moderate chromium content ensures a degree of corrosion resistance, though less than that of austenitic grades such as AISI 304.
Chemically, the alloy forms a passive Cr2O3 film that offers protection against oxidation and mild corrosive environments. The carbon content promotes carbide formation (primarily Fe3C), which enhances hardness and wear resistance. The steel’s response to thermal and mechanical treatments enables property tuning through processes such as annealing, normalizing, and tempering, allowing optimization for specific operational requirements (Lenda et al., 2020).
Applications and Advantages
Tooling and manufacturing. AISI 420 is widely used in the production of cutting tools, injection molds, dies, and surgical instruments, where high hardness and wear resistance are critical (McGuire, n.d.). It maintains dimensional accuracy and strength under cyclic loading, making it suitable for precision tooling applications. In mold-making industries, its polishability and ability to achieve mirror finishes are particularly valued.
Engineering and high-temperature components. The alloy performs well in automotive and aerospace applications that require mechanical reliability under thermal stress. The introduction of copper (Cu) through hot pressing can significantly improve thermal conductivity, allowing efficient heat dissipation in components such as valves and heat exchangers (Cunha et al., 2023). Its ability to maintain hardness and strength at elevated temperatures further extends its use in wear-intensive and thermally demanding environments.
Advanced processing and additive manufacturing. AISI 420 is compatible with modern manufacturing techniques, including laser powder bed fusion (LPBF), enabling the fabrication of complex geometries for high-performance applications (Nath, 2018). These additive manufacturing methods produce dense, defect-minimized parts with tunable mechanical properties. Surface engineering processes like ionic nitriding also enhance fatigue life and surface performance (Júnior, 2008).
Heat Treatment and Microstructural Control
Heat treatment significantly influences the mechanical and corrosion behavior of AISI 420. Annealing between 250°C and 650°C reduces hardness due to cementite spheroidization, improving machinability (Lenda et al., 2020). Quenching from higher temperatures (980–1050°C) followed by tempering produces a fine martensitic structure, balancing toughness and wear resistance. Plasma oxy-nitriding further enhances surface performance while maintaining the integrity of the substrate (Kim & Lee, 2023).
Goodfellow Availability
Goodfellow supplies AISI 420 (Fe86.7/Cr13.0/C0.3) stainless steel wire and other product forms for scientific, engineering, and tooling applications. Our materials are precision-manufactured to ensure uniform microstructure, high surface quality, and predictable heat-treatment response. Custom dimensions, finishes, and processing options are available upon request.
Explore AISI 420 Stainless Steel and related martensitic grades in Goodfellow’s online catalogue: Goodfellow product finder.
References
- Kim, J.-H., & Lee, K.-M. (2023). Surface Hardness and Corrosion Behavior of AISI 420 Martensitic Stainless Steels Treated by Plasma Oxy-Nitriding Processing. https://doi.org/10.3740/mrsk.2023.33.7.309
- Nath, S. D. (2018). Process-Property-Microstructure Relationships in Laser-Powder Bed Fusion of 420 Stainless Steel. https://doi.org/10.18297/ETD/3074
- Júnior, A. (2008). Nitretação iônica em gaiola catódica do aço inoxidável martensítico AISI 420. https://doi.org/10.1590/S1517-70762008000100012
- Hasenberg, L., & Bender, R. (n.d.). Ferritic‐Austenitic Steels with More Than 12% Chromium. https://doi.org/10.1002/9783527610433.chb03222
- McGuire, M. F. (n.d.). Stainless Steels for Design Engineers. https://doi.org/10.31399/asm.tb.ssde.9781627082860
- Lenda, O. B., Tara, A., Lazar, F., Jbara, O., Hadjadj, A., & Saad, E. (2020). Structural and Mechanical Characteristics of AISI 420 Stainless Steel After Annealing. https://doi.org/10.1007/S11223-020-00151-4
- Cunha, A., Pinto, J. D. da S., Cerqueira, M., Silva, F., Trindade, B., & Carvalho, O. (2023). Development and Production of a CNC Machined 420 Stainless Steel Reinforced with Cu by Hot Pressing. https://doi.org/10.1007/s10853-023-08332-7