What instrumented indentation tells you
Hardness and stiffness determine how a material resists scratching, wear, deformation and contact damage. Instrumented indentation measures both at the scale that matters: a thin film, a coating, a single grain, a polymer surface, a biological tissue. Because load and depth are recorded throughout, each indent also shows elastic recovery, creep during the hold, and events such as cracking or pop-in.
How the test works
- The indenter approaches the surface and detects contact.
- Load increases to a set maximum at a controlled rate. The independent depth sensor records penetration throughout.
- The load is held, often to let creep settle, then removed while depth is still recorded.
- The software analyses the unloading curve to obtain contact stiffness and contact depth, then calculates indentation hardness and elastic modulus.
Repeating this over a grid produces a property map. With position control to 0.2 µm, NANOVEA’s fast mapping study placed 625 indents in 0.20 mm² to reveal grains and porosity in a ceramic.
Nano and micro in one system
NANOVEA mechanical testers carry nano and micro load modules, together spanning five orders of magnitude of load. The nano module measures thin films, soft materials and individual phases at mN loads. The micro module replaces conventional microhardness testers: one module covers 0.3 g to 2 kg or 6 g to 40 kg, and NANOVEA’s micro module study ran Vickers indents on steel from 0.03 N to 200 N on a CB500.
Why the measurement architecture matters
Loads are applied vertically, with no cantilever or pivot that could introduce lateral motion or compliance, and measured by a load cell independent of the actuator. Depth is measured by a capacitive sensor. The two sensors run in a true closed feedback loop, so the set load is what is actually applied, even while the material creeps.
Indenter geometry
- Berkovich: the standard nanoindentation tip; its three faces meet at a point that stays sharp at small depths.
- Vickers: four-sided, for microhardness comparable with conventional testers.
- Knoop: elongated, giving shallow indents suited to thin layers and to measuring anisotropy.
- Conical and spherical: for soft materials and for stress–strain studies, where the gradual transition from elastic to plastic contact is useful.
Testing in service conditions
Hardness and modulus change with temperature, moisture and immersion, especially for polymers. NANOVEA’s humidity-controlled study measured a polymer film’s hardness falling from about 0.60 GPa to 0.31 GPa as relative humidity rose from 25% to 75%, with creep depth increasing alongside. Environmental modules let the same measurement run hot, cold, humid, immersed or in vacuum.
