AISI M35 Cobalt-Bearing High-Speed Steel
AISI M35 — 5 % Co M2 modification, hot hardness HRC 60 at 600 °C. Compare with M2 and M42 for high-speed slitter blades (>800 m/min).
AISI M35 (UNS T11335) is a 5 % Co modification of M2 — the cobalt boosts hot hardness from HRC 56 (M2 at 600 °C) to HRC 60 (M35 at 600 °C), extending edge life in high-temperature cutting. Hardened to HRC 63–66, it is used for high-speed slitter blades (>800 m/min on tissue / film) and dry cutting applications where M2 hot hardness is marginal.
Standard composition: C 0.80–0.90 %, Cr 3.75–4.50 %, Mo 4.50–5.50 %, W 5.50–6.75 %, V 1.75–2.25 %, Co 4.50–5.50 %, Mn ≤ 0.40 %, Si ≤ 0.50 %, balance Fe
Hardness: Annealed HB 235–269; hardened HRC 63–66
Heat treatment: Austenitise 1,200–1,225 °C, oil or salt quench, double temper 540–565 °C
Properties: The 5 % Co addition boosts hot hardness to ~ HRC 60 at 600 °C (vs M2 HRC 56). Better edge retention at high temperature. Toughness slightly lower than M2.
Applications: High-speed slitter blades (>800 m/min on tissue or film), foil slitting, dry cutting applications.
Cross-reference: ≈ JIS SKD55, DIN 1.3243, GB W6Mo5Cr4V2Co5, BS BM35.
See also.
