ISO 24674:2022

Overview

ISO 24674:2022 specifies a method and requirements for combining plasma nitriding with follow‑up PVD hard coatings (a duplex treatment) for cold‑work mould steels. The standard sets out metallurgical prerequisites, process controls, surface quality limits and adhesion evaluation criteria to achieve an optimal duplex system that improves wear resistance, loading capacity and coating lifetime for cold‑work tools used e.g. in the automotive sector.

Key topics and technical requirements

• Substrate requirements
  • Typical acceptance hardness: HRC45 to HRC60 (Rockwell test per ISO 6508‑1).
  • Original microstructure classes (1–5) are defined by optical microscopy (×500); Classes 1–2 are acceptable.
• Plasma nitriding
  • Surface roughness (Rz) before nitriding: < 1 μm; surface must be clean and oxide‑free.
  • Protection of areas not to be nitrided (masking); blind deep holes to avoid hollow‑cathode effects.
  • Process parameters (reactive gas, temperature, time, pressure) control formation of a compound layer and an underlying diffusion zone. For thin‑walled parts use lower temperature + longer holding time.
  • Example parameter ranges are given in the standard (by alloying fraction), illustrating temperature and hold‑time tradeoffs.
• PVD coating preparation and deposition
  • If a compound layer forms, it must be mechanically ground/polished away prior to PVD to ensure adhesion; final surface roughness after treatment: Rz < 1 μm.
  • Substrate cleaning should follow ISO 27831‑1.
  • PVD coating design should consider roughness, friction coefficient, toughness and anti‑sticking for cold‑work applications.
• Metallurgical inspection and testing
  • Nitriding case depth: measured from at least five points per ISO 18203.
  • Diffusion layer nitride distribution and brittleness are classified visually (optical microscopy ×500) and by Vickers impressions (98.1 N) into classes 1–5; Classes 1–2 are acceptable for brittleness.
  • Adhesion of the duplex coating: indentation test (load 1 471.5 N, per guidance from ISO 26443) with defined acceptable crack/spall patterns.

Applications and who uses this standard

• Primary application: cold‑work moulds used in forming, cold extrusion, powder compacting and other high‑wear, high‑pressure tooling-commonly in the automotive supply chain.
• Intended users:
  • Tool and die manufacturers, heat‑treat and surface‑engineering shops
  • PVD coating suppliers and process engineers
  • Quality managers and materials testers specifying acceptance criteria
  • OEMs and Tier suppliers seeking standardized duplex treatment specifications to increase tool life and reduce failures (abrasive wear, galling, delamination)

Related standards

• ISO 6508‑1 - Rockwell hardness test (metallic materials)
• ISO 27831‑1 - Cleaning and preparation of ferrous metal surfaces
• ISO 18203 - Thickness of surface‑hardened layers (nitriding case depth)
• ISO 26443 - Indentation test for adhesion evaluation (reference for duplex adhesion method)

Keywords: ISO 24674:2022, plasma nitriding, PVD hard coatings, duplex treatment, cold‑work mould steels, nitriding case depth, compound layer, diffusion layer, adhesion testing, surface roughness, tool life.