1. Tensile Strength
Common grades like Monel 400 have a tensile strength of approximately 65,000–90,000 psi (448–621 MPa) in the annealed state. Cold working (e.g., rolling or forging) can increase this to 100,000–150,000 psi (689–1,034 MPa).
Precipitation-hardened grades like Monel K-500 offer even higher tensile strength, reaching 180,000–200,000 psi (1,241–1,379 MPa) after heat treatment, due to the formation of intermetallic precipitates that strengthen the alloy.
Mild (low-carbon) steel: Tensile strength ranges from 40,000–60,000 psi (276–414 MPa), making it weaker than most Monel grades.
High-strength low-alloy (HSLA) steel: Tensile strength typically falls between 60,000–100,000 psi (414–689 MPa), overlapping with annealed Monel 400 but generally lower than cold-worked or K-500 Monel.
Alloy steels (e.g., 4140, 4340): Heat-treated versions can reach 150,000–250,000 psi (1,034–1,724 MPa), exceeding even Monel K-500.
Tool steels or maraging steels: These can achieve tensile strengths of 250,000–300,000 psi (1,724–2,068 MPa) or higher, far surpassing all Monel grades.
2. Yield Strength
Annealed Monel 400 has a yield strength of ~25,000–40,000 psi (172–276 MPa). Cold working raises this to 60,000–120,000 psi (414–827 MPa).
Monel K-500, after aging, offers yield strengths of 140,000–160,000 psi (965–1,103 MPa).
Mild steel: Yield strength is ~20,000–30,000 psi (138–207 MPa), lower than annealed Monel.
HSLA steel: Yield strengths range from 40,000–80,000 psi (276–552 MPa), comparable to cold-worked Monel 400 but lower than K-500.
Heat-treated alloy steels (e.g., 4340): Yield strengths can exceed 200,000 psi (1,379 MPa), outperforming Monel K-500.
3. Hardness
Annealed Monel 400 has a Brinell hardness (HB) of ~110–150. Cold working increases this to ~200–250 HB.
Monel K-500, when aged, reaches ~250–300 HB.
Mild steel: ~120–150 HB, similar to annealed Monel 400.
HSLA steel: ~180–220 HB, overlapping with cold-worked Monel 400.
Heat-treated alloy steels (e.g., 4140 quenched and tempered): ~250–350 HB, exceeding most Monel grades.
Tool steels (e.g., D2): Can reach 60+ HRC (equivalent to ~600+ HB), far harder than any Monel.
4. Toughness and Impact Resistance
Mild steel and HSLA steel offer excellent toughness at room temperature but can become brittle in cold environments unless alloyed with nickel (e.g., 3.5% nickel steel for cryogenic use).
High-strength alloy steels may have reduced toughness when fully hardened, requiring tempering to balance strength and ductility.
