Scratch hardness test
The scratch hardness test measures the strength of a surface by the penetration of a defined scratch tip. It indicates how resistant a surface is to scratching or abrasion.
Physical-Chemical Mechanism of Action
The scratch hardness test uses a hardened rod (scratch tip) that is pressed into the surface to be tested. The depth of penetration is measured and converted to the hardness of the surface.
Metallurgical Relevance & Welding Risks
The scratch hardness provides information about local surface hardness and the adhesion of coatings. If hardness is too low, material can wear away prematurely, leading to early failure. Excessively hard material can cause stress buildup and cracking.
Workshop Practice & Instructions
Use a scratch tip with a defined angle (e.g., 120°) and a fixed length. Press the tip onto the surface to be tested and penetrate slowly to the desired depth. Measure the depth of penetration and use a hardness curve to convert the hardness value (e.g., HB).