Microhardness Testing
Microhardness testing determines hardness at a microscopic level. It's done with diamond indenters like Vickers or Knoop and reveals local hardness variations.
Physical-Chemical Effect Mechanism
Microhardness testing measures hardness in a very small area, typically in the micrometer range. A pyramidal diamond indenter is pressed into the material, and the size of the resulting indentation is measured. Hardness is calculated from the force divided by the area of the indentation.
Metallurgical Relevance & Welding Risks
Microhardness testing is crucial for quality control of weld zones. It reveals local hardness variations caused by uneven cooling or chemical changes. Too high microhardness can lead to crack-sensitive structures, while too low values mean lower toughness and scale resistance.
Workshop Practice & Action Instructions
For microhardness testing, a special microhardness tester is used. The indenter is pressed into the test material, and the indentation size is measured under a microscope. Hardness is then calculated using the formula: Hardness = Force / Area. It is important to control the cooling of the material to ensure homogeneous hardness distribution.