Question

The Vicker’s diamond pyramid method of hardness determination does not give accurate result, when employed for the

• A. Hard metals
• B. Forged parts with rough surface
• C. Soft metals
• D. Polished and hardened steel surface

Hint:

The Vickers hardness test is best applied on smooth, polished surfaces—rough surfaces distort the indent shape and lead to inaccurate readings.

Answer 1

The Correct Option is B

Step 1: Understanding Vickers Hardness Test The Vickers hardness test uses a diamond pyramid indenter and is best suited for very small or polished surfaces. It measures the diagonals of the indentation left after applying a known force. Step 2: Limitation on Rough Surfaces - The Vickers test assumes a smooth and flat test surface for precise measurement of indentation. - On rough surfaces like forged parts, the irregularities distort the shape of the indentation, making accurate measurement of the diagonal lengths difficult. - This leads to erroneous hardness values due to surface unevenness and scattering of light during optical observation. Step 3: Other Options Analysis - \textit{Hard metals:} Vickers test is actually designed for hard materials due to diamond indenter. - \textit{Soft metals:} Can be tested, although Brinell may be more suitable for some. - \textit{Polished and hardened surfaces:} Ideal for Vickers, providing sharp, measurable indentations.