What is a Knoop indenter?
The Knoop indenter is more elongated or rectangular in shape. The Knoop method is commonly used when indentations are closely spaced or very near the edge of the sample. The width of the Knoop indentation can provide more resolution for measurement and the indentation is also less deep.
What is HK in hardness?
The final Knoop hardness (HK) is derived from the following formula: HK = 14.229(F/D2), with F being the applied load (measured in kilograms-force) and D2 the area of the indentation (measured in square millimetres). Knoop hardness numbers are often cited in conjunction with specific load values.
Under what circumstances is the Knoop micro hardness test usually used?
DEFINITION OF THE KNOOP HARDNESS TEST It is mainly used to overcome cracking in brittle materials, as well as to facilitate the hardness testing of thin layers.
What is the shape of Knoop indenter?
The Knoop hardness test uses a rhombohedral-shaped diamond indenter. The long diagonal is seven times (7.114 actually) as long as the short diagonal.
Which two of the following hardness tests use a pyramid shaped indenter?
B Hardness Testing. where P is the load and d is the average length of the diagonals of the square impression. The Vickers test uses a pyramidal indentor with a square base. In the Rockwell test, the hardness is read directly from a dial in the machine.
What is a microhardness test and what is its name?
The Knoop hardness test is also a microhardness technique that is similar to the Vickers hardness test method. A Knoop indenter is used to press into a surface to measure hardness.
What is HK25?
The values are expressed like 2500 HK25 (or HV25) meaning 2500 Hardness Knoop at 25 gram force load. The Knoop and Vickers hardness values differ slightly, but for hard coatings, the values are close enough to be within the measurement error and can be used interchangeably.
Why is diamond used as indenter?
The diamond cone is used for the hardest materials, and hardness numbers on the A, C, and D scales are obtained by applying the indicated loads and measuring the indentation depth. These tests are non-destructive and the hardness numbers obtained may be correlated with material elastic and plastic properties.
What is the difference between microhardness and hardness?
Hardness testing is divided into two ranges: macrohardness and microhardness. Macrohardness covers testing with an applied load over 1 kg or about 10 Newton (N). Microhardness testing, with applied loads under 10 N, is typically used for smaller samples, thin specimens, plated surfaces or thin films.
What does HV mean in hardness?
The Vickers Hardness (HV) is calculated by optically measuring the diagonal lengths of the impression left by the indenter. The measurements are converted to HV using a table or formula. Load range: From 10 gf up to 100 kgf.