· KAIPU Engineering · materials-encyclopedia · 1 min read
AISI M42 Cobalt-Bearing Super High-Speed Steel
Materials encyclopedia entry for M42.
AISI M42 Cobalt-Bearing Super High-Speed Steel is a reference entry for industrial cutting tools and blades. The composition, hardness, heat treatment and application guidance are summarised below for engineering reference.
Standard composition: C 1.05–1.20 %, Cr 3.50–4.50 %, Mo 9.00–10.00 %, W 1.15–1.85 %, V 0.95–1.35 %, Co 7.75–8.75 %, Mn ≤ 0.40 %, Si ≤ 0.50 %, balance Fe
Hardness: Annealed HB 235–269; hardened HRC 65–69
Heat treatment: Austenitise 1,180–1,200 °C, oil or salt quench, double temper 510–530 °C
Properties: The 8 % Co addition gives the highest hot hardness of any standard HSS. Hardness up to HRC 69 achievable. Wear life 1.5–2× M2 on abrasive substrates. Toughness lower than M2.
Applications: High-speed slitter blades (>1,200 m/min on tissue), high-temperature cutting, foil slitting with ta-C coating.
Cross-reference: ≈ JIS SKD59, DIN 1.3247, GB W2Mo9Cr4VCo8, BS BM42.
See also: D2 vs SKD11 comparison, Material Grade Converter, The KAIPU 5-Factor Blade Selection Framework.