May 30, 2026 · Publication · Test technology

Instrumented indentation and the load–displacement curve (ISO 14577)

Instrumented indentation testing (nanoindentation) provides far more than a single hardness value: it records the load–displacement curve while the indenter penetrates the surface. From this curve, properties such as Martens hardness HM, indentation hardness HIT and the indentation modulus EIT are determined – a solid basis for the mechanical characterisation of bulk materials and coatings, especially where local surface response matters more than bulk assumptions, and a key input for modern indentation plastometry workflows related to ASTM E3499.

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Nanoindentation: mapping of mechanical properties via instrumented indentation
Fig. 1 – Nanoindentation mapping

What does a load–displacement curve reveal beyond a single hardness value?

The load–displacement curve separates elastic and plastic contributions and enables determination of the indentation modulus (EIT). Typical properties defined by ISO 14577 include:

“Martens hardness HM, indentation hardness HIT, indentation modulus EIT.”

Beyond this, material differences, coatings and gradients can be evaluated with spatial resolution. For high data quality, a low-vibration environment and suitable surface preparation are essential – excessive roughness or vibration affects the results. Typical application fields include failure analysis, coating characterisation, quality assurance and the testing of miniaturised components. In many of these cases, macro tests would average out the local behaviour that is actually relevant for the engineering decision. The method is standardised by ISO 14577 and provides the raw data that can also be used in indentation plastometry and ASTM E3499-style evaluations of plastic behaviour.

Which results can be extracted from a load–displacement curve?

The load–displacement curve (F–h) is recorded in mN (load) and nm (penetration depth). From the unloading segment according to ISO 14577, the indentation modulus (EIT) is determined. Additional properties are derived from Martens hardness (HM) and indentation hardness (HIT). Such curves are also a starting point for inverse modelling in indentation plastometry approaches inspired by ASTM E3499.

Property Value (example) Unit
Martens hardness HM 2.45 GPa
Indentation hardness HIT 2.10 GPa
Indentation modulus EIT 205 GPa
Maximum load Fmax 50 mN
Maximum penetration depth hmax 2000 nm

Load–displacement curve (F–h), example nanoindentation measurement (ISO 14577).

Which questions are frequently asked about instrumented indentation under ISO 14577?

Which properties are determined according to ISO 14577?

Martens hardness HM, indentation hardness HIT, indentation modulus EIT and further parameters derived from the load–displacement curve. These properties can also serve as input for indentation plastometry studies in line with ASTM E3499 concepts.

What is important for specimen preparation?

Appropriate surface preparation with low roughness and a stable, low-vibration test environment are essential for reproducible results – both for standard ISO 14577 testing and for downstream indentation plastometry evaluations.

Authors · Contributors

Testawell editorial team, Peter Zok

Peter Zok

Peter Zok

Applications – Materials Testing

Testawell

15 years of experience in materials testing.

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