Microhardness Testing

Microhardness testing shall be performed in accordance with ASTM E384 unless otherwise specified by the client If the client does identify an alternative test method or procedure, it shall be documented on Lab work-sheet Microhardness is performed by two methods. Knoop (HK) and Vickers(HV).

Questions: What would I use Microhardness testing for?

Answer: Microhardness testing gives you the advantage of testing materials hardness on very thin layers or sheet. It also allows you to measure case hardness and the depths of case hardness. It can also be used in to determine decarburization depth or verification that limits were not exceeded during the heat treatment process.

CMS uses Knoop for microhardness from 10g to 500g load evaluation- The number obtained by dividing the applied load in kilograms force by the projected area of the indentation in square millimeters, computed from the measurement of the long diagonal of the indentation. The Knoop number can then be converted by ASTM E 140 to Rockwell, Brinell or any other desired scale requested. Please remember that some scales may fall out of conversion requested.

The mounted specimen submitted for evaluation will be set for proper parallel requirements by using mounting clay and press. The plane of the surface of the specimen shall be perpendicular to the axis of the direction of the load application. The specimen shall be examined at the following magnifications.

Under proper magnification (400X), select area to be tested, which is determined by customer requirements or drawings, and support specimen so that the surface is normal to the axis of the indenter and the ends to the diagonals are clearly defined. Make sure diamond is clean before starting the testing procedure. Make indention by releasing load, load is applied for a period of 10 to 20 seconds. After load is completed, bring the ends of the diagonals into sharp focus. Bring the edge of the ocular or graduation line just into contact with the end of the diagonals. These measurements are done by using stage micrometer located on the ocular portion of the tester.