DIN 50190-3 is a DIN method used to determine the effective hardened depth after nitriding by evaluating a hardness profile from the surface into the core material.
This standard is most often referenced when you need a measurable “case depth” value from a microhardness traverse for nitrided or nitrocarburized steel parts. If you need help matching the right preparation steps and hardness equipment to your part geometry, you can contact our team.
DIN 50190-3: Härtetiefe wärmebehandelter Teile; Ermittlung der Nitrierhärtetiefe
DIN 50190-3 defines a hardness-based approach for determining nitriding hardness depth (often abbreviated NHD) on heat-treated parts after nitriding.
DIN lists DIN 50190-3:1979-03 as withdrawn and indicates it has been replaced by DIN EN ISO 18203:2022-07. In practice, DIN 50190-3 is still encountered in drawings, legacy specifications, and customer-specific acceptance criteria.
Quick Definition
DIN 50190-3 in one line: A method to determine nitriding hardness depth from a hardness-vs.-distance curve measured on a prepared cross section.
What you get from the test: A depth value (distance from the surface) corresponding to the specified hardness limit used to define the effective nitrided case.
What This Standard Covers
This standard provides a procedure to determine nitriding hardness depth using hardness measurements taken from the surface toward the core.
It is intended for nitrided parts regardless of the specific nitrided layer condition, and it includes limitations for cases where the hardness gradient is too shallow to evaluate reliably (for example, when the surface-to-core hardness difference is small).
Why This Standard Matters in Testing
Nitriding and nitrocarburizing are often specified to improve wear resistance and fatigue performance by creating a hardened near-surface zone. A hardness-depth evaluation is a common acceptance tool because it converts a hardness traverse into a single, comparable depth value.
For QA/QC teams and heat treaters, DIN 50190-3 helps align incoming/outgoing inspection, supplier documentation, and engineering requirements around a defined hardness limit rather than visual or subjective layer interpretation.
Common Materials, Product Types, or Applications Covered
DIN 50190-3 is commonly associated with nitrided ferrous parts where effective hardened depth is specified or needs to be reported.
Common part examples: Gears, shafts, pins, valve components, tooling elements, and other wear- or fatigue-critical steel components that have been nitrided or nitrocarburized.
Common Test or Verification Workflow
A typical DIN 50190-3 workflow is a cross-sectional hardness traverse that produces a hardness profile from the surface into the base material.
Common workflow steps:
- Section the part (or a representative coupon) to expose a cross section through the nitrided zone.
- Mount, grind, and polish the cross section to a finish suitable for reliable microindentation near the edge.
- Measure core hardness and build a hardness traverse at defined intervals from the surface inward (commonly using Vickers low-load/microhardness techniques).
- Determine the nitriding hardness depth from the hardness curve using the hardness limit defined by the standard and/or the controlling specification.
- Report the measured depth, test conditions (method/load), and the hardness profile details needed for traceability.
Practical caution: Edge preparation quality and indentation spacing strongly affect repeatability. Thin cases, strong gradients, or limited flat area may require smaller test loads and tighter control of surface finish and measurement spacing.
Equipment Commonly Used for This Standard
DIN 50190-3 is primarily a hardness-testing workflow. Equipment selection is driven by case depth, gradient steepness, available measurement area, and the minimum allowable distance from the surface for the first valid indentation.
Common equipment: Microhardness tester (typically Vickers), optical measurement system/software for indentation evaluation, metallographic sectioning saw, mounting press (hot or cold), grinding/polishing system, and a metallographic microscope for verification and documentation.
What to plan for when specifying a system: Stable test force at low loads, repeatable stage positioning for traverses, image quality suitable for small indents, and software that supports hardness traverses and reporting.
If you are selecting a microhardness system for nitrided case-depth work, you can request a detailed quote based on your expected case depth range, part geometry, and throughput targets.
How to Read This Designation or Revision
DIN 50190-3 identifies Part 3 within the DIN 50190 series and is focused on nitriding hardness depth determination.
Edition notation: DIN citations often include a date such as DIN 50190-3:1979-03, which indicates the month and year of issue. Test setup and reporting expectations can depend on the cited edition and on any additional requirements in a customer or product specification.
Status note: DIN 50190-3:1979-03 is listed by DIN as withdrawn and replaced by DIN EN ISO 18203 (edition 2022-07). When a drawing calls out DIN 50190-3, confirm whether the customer expects strict adherence to the legacy DIN requirement or acceptance to the replacement standard.
Related Standards, Methods, or Frameworks
DIN 50190-3 is commonly used alongside microhardness methods (for example, Vickers hardness testing) because nitriding hardness depth is derived from a hardness traverse rather than from a single indentation.
Where specifications require a more current reference, DIN indicates DIN EN ISO 18203 as the replacement for DIN 50190-3. Always follow the exact standard and edition cited in the controlling document unless the customer formally approves a substitution.
Talk with us about DIN 50190-3 testing capacity
If you need to build or upgrade a nitrided case-depth measurement workflow (sample prep, microhardness capability, traverse automation, and reporting), talk with our team about a setup that fits your materials and the exact standard callout on your print.