410 vs 420 Martensitic Stainless Steels: Weldable Moderate Strength vs High-Hardness Wear Resistance

 

What are their core compositions and mechanical property differences?

410 contains 11.5–13.5% Cr, ≤0.15% C, and no nickel. In the annealed state, it has a tensile strength of ~520 MPa, and it can be heat-treated to a hardness of ~45 HRC for moderate wear resistance. Its low carbon content enables better weldability than higher-carbon martensitic grades.420 features 12–14% Cr, 0.15–0.40% C, and no nickel. With heat treatment (quenching and tempering), it reaches a maximum hardness of 55 HRC. Its higher carbon content forms dense chromium carbides, boosting wear resistance but significantly reducing weldability.Both grades are magnetic at all temperatures and require heat treatment to achieve their full strength potential.

How do their weldability and formability differ for fabrication?

410 is the most weldable martensitic stainless steel-it can be welded using standard GTAW or SMAW methods, with preheating to 150–200°C and post-weld tempering to eliminate residual stress and avoid cracking. It also has good formability for bending and stamping thin-gauge parts.420 has poor weldability due to its higher carbon content: welding causes carbide precipitation at grain boundaries, leading to brittleness and cracking in the heat-affected zone. Welding 420 is not recommended for critical load-bearing components, even with preheating.420's formability is limited to mild bending-severe cold working without intermediate annealing will cause work hardening and cracking.

In which applications is one grade preferred over the other?

Choose 410 for welded mechanical parts in dry environments: pump shafts, valve bodies, agricultural equipment components, and furnace burners where moderate strength and weldability are critical requirements.Opt for 420 for non-welded, wear-intensive parts: cutting tools for wood or plastic, surgical instruments like scalpels, firearm components, and bearing races that demand high hardness and edge retention.

How do their corrosion resistances compare in service environments?

410 offers basic corrosion resistance, tolerating dry indoor conditions and short-term exposure to freshwater. It will rust quickly in humid, coastal, or mild chemical environments without protective coatings like galvanizing or powder coating.420's higher carbon content reduces its corrosion resistance compared to 410, making it even more susceptible to rust in moist settings. It is only suitable for dry, low-moisture applications like indoor machinery gears or small cutting tools.Neither grade is recommended for marine, chemical, or food-processing applications-upgrade to 304 or 17-4 PH for better corrosion protection.

What are the key heat treatment guidelines for each grade?

For 410, the standard hardening cycle is: austenitize at 980–1050°C, quench in oil, then temper at 200–300°C to balance hardness and toughness. Tempering above 300°C will reduce strength but improve ductility and corrosion resistance slightly.For 420, use a higher austenitizing temperature (1010–1070°C) to fully dissolve carbides, followed by oil quenching and tempering at 150–200°C to maximize hardness. Avoid over-tempering, as this will significantly reduce wear resistance.Both grades must be cooled slowly after annealing to prevent embrittlement-rapid cooling can cause cracking in thick sections.