Define the hardness of metal How is the hardness of a materi

Define the hardness of metal. How is the hardness of a material determined by hardness testing machines? (2 points) 3.

Solution

Hardness of Metal - Hardness is the property of metal due to which it resist permanent identation or scratch.it is surface property and can be improved by certain heat treatment process.

A hard metal can abrade material from a soft metal on rubbing

Diamond is the Hardest known material.

Rockwell and Brinell test are used ti find Hardness.

The Rockwell hardness is based on difference of indentation depth of indenter from two different load applications. First minor load is applied to achieve zero level then major load is applied for specific period. Major load creates additional penetration from zero level. After dwell time major load is removed while minor load is still applied. Resulting Rockwell number is difference in depth from zero level.

In Brinell hardness test hard ball indenter is pressed under load on surface of material. It is there for set dwell time to achieve equilibrium, then indenter and load is withdrawn from surface. Diameter of indentation thus formed is measured. The Brinell hardness number is expressed as ratio of load and area of indentation.