Low-Load Vickers Microindentation Hardness Testing

ADVANCED MATERIALS & PROCESSES • APRIL 2012 I n 1925 in the UK, Smith and Sandland developed an indentation test that used a squarebased pyramidal-shaped indenter made of diamond[1]. The test was developed because the Brinell test (introduced in 1900), which (until recently) used a round hardened steel ball indenter, could not test steels harder than ~450 HB (~48 HRC). They chose this shape with an angle of 136° between opposite faces to obtain hardness numbers that would be as close as possible to Brinell hardness numbers for the same specimens over the usable Brinell range. This made the Vickers test easy to adopt, and it rapidly gained acceptance. The Vickers test has the great advantage of one hardness scale being used to test all materials, unlike the 30 different Rockwell test scales, each yielding numbers between ~20 and ~100. In the Vickers test, the force is applied smoothly, without impact, and held in contact for 10 to 15 seconds. The force must be controlled precisely. After removing the force, both diagonals are measured and the average is used to calculate the HV according to (for loads £1 kgf):