Overview
ISO 4507:2000 specifies micro-hardness test methods for determining and verifying the case-hardening depth (CHD) of sintered ferrous materials that have been carburized or carbonitrided. The standard is intended for quenched (hardened) sintered parts and is adapted for materials with porosity. Testing is based on Vickers micro-hardness measurements (HV 0.1, 0.9807 N) performed on a transverse section perpendicular to the treated surface.
Key benefits:
- Enables objective verification of case depth for quality control and acceptance testing
- Designed for porous, sintered ferrous materials (carburized or carbonitrided)
- Defines both detailed and rapid inspection procedures for production and laboratory use
Key Topics
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Test principle: Vickers micro-indentations are made at increasing depths from the surface and hardness is plotted against distance to determine CHD at a specified hardness (normal reference: 550 HV 0.1).
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Methods:
- Method A (graphical): Multiple indentations at standardized depths (examples: 0.05, 0.1, 0.2, 0.3, 0.4, 0.5, 0.75, 1, 1.5, 2, 3 mm). Average hardness values per depth are plotted and the CHD is read where the hardness curve intersects the horizontal line at the specified hardness (HG, typically 550 HV 0.1).
- Method A (modified): When porosity or microstructure prevent standard depth spacing, individual readings may be plotted directly and fitted to determine intersection with HG.
- Method B (rapid control): Two depths are tested (one shallower, one deeper than estimated CHD) with multiple indentations; CHD is derived by graphical interpolation or by a calculation formula provided in the standard.
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Apparatus & preparation: Requires a Vickers or Knoop micro-hardness tester capable of HV 0.1 load, accurate diagonal measurement instrumentation, and careful metallographic sectioning and polishing (imbedding/impregnation of porous samples may be used).
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Fidelity: Interlaboratory data reported by MPIF indicate repeatability and reproducibility benchmarks (for CHD = 0.75 mm: repeatability ~0.14 mm, reproducibility ~0.47 mm at 95% confidence).
Applications
- Incoming inspection and acceptance testing of sintered gears, bushings, and powertrain components after carburizing or carbonitriding
- Process control during heat treatment and surface engineering operations
- Failure analysis where verification of effective case depth is required
Related Standards
- ISO 2639 - Steel - Determination and verification of conventional case depth
- ISO 4498 - Metallic materials, sintered - Determination of apparent hardness and microhardness (reference for Vickers/Knoop modes)
- MPIF 52 - Report on case hardening effectiveness (interlaboratory study referenced in ISO 4507)
For laboratory reporting, ISO 4507:2000 specifies required test details (method used, HG value, specimen identification, location of test area, results and any deviations), supporting traceable and reproducible CHD verification for quality assurance.
Open preview (PDF)Sintered ferrous materials, carburized or carbonitrided — Determination and verification of case-hardening depth by a micro-hardness test