Nano, Micro, Vickers & Rockwell Hardness
Quick Guide
Indentation Testing
Hardness
Elastic Modulus
Creep
Fracture Toughness
Scratch Testing
Adhesion
Scratch Resistance
Wear
Pin-on-Disk
Linear Reciprocating
Coefficient of Friction
Static
Dynamic
Dynamic with wear
Mechanical Testing
Tensile
Compression
Flexural
Shear
Profilometry
Data Processing
Service
Ellipsometry
Training & Consulting
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Indent on a rough surface |
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Precise positioning of indent |
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Fused silica |
Instrumented indentation: Many rely on conventional micro hardness measurement technique to obtain hardness values, in which cases, hardness is computed using the diagonals of an imprint.
While the technique works well for bulk materials and thick coatings, it is not appropriate for small features, thin coatings and materials such as glass and ceramics that crack under too much load. Also, the smaller the indent, the greater the error on the measurement.
This is why EP Laboratories also uses instrumented indentation as a mean to obtain hardness values. Instrumented indentation is based on the analysis of the load-penetration curve measured while doing an imprint.
It is computer-controlled and it is not influenced by the operator's judgment of the imprint's shape. Properties such as hardness, creep and elastic modulus can be determined with a single indent. Many are mistakenly using conventional measurement techniques when they should use instrumented indentation.
Keep the following in mind when choosing a hardness testing technique:
- A hardness value is invalid if an indent shows sign of cracking or pile up;
- Ideally an indent should not be deeper than 1/7 to 1/10 of the coating thickness;
- When measuring the hardness of a coating using a cross-section, the distance between the edge of coating (surface/interface) and the indent itself should be at least 3 times the size of the diagonals;
- The hardness of most samples can be measured using instrumented indentation without the necessity to have a polished cross-section.
