Hardness Equipment
Classification of Hardness Tests
Active element or tool Line of action of load applicator Fixed load; variable indentation or attrition Fixed indentation or attrition; variable load Static Dynamic Static Dynamic Two specimens, one pressed against the other Normal to specimen Reaumur (1722) Tool of material harder than specimen Normal to surface of specimen Brinell (1900)
Rockwell (1920)
Vickers (1925)
Knoop (Tukon) (1939)Shore scleroscope (1906)
Ballentine
Cloudburst
Schmidt
Various abrasion tests -- e.g. sandblast typeMonotron
Wood-hardness toolParallel to surface of specimen Marten sclerometer (1889)
Bierbaum sclerometer
Herbert pendulum (1923)
Machinability (cutting, drilling) tests
Various wear or abrasion testsAllcut and Turner sclerometer (1887)
Various qualitative scratch-hardness tests -- Mohs (1822)From The Testing and Inspection of Engineering Materials, 3rd Ed., by H.E. Davis, G.E. Troxell, and C.T. Wiskocil, McGraw-Hill, 1964, p. 186.
Static indentation tests: A ball, cone, or pyramid is forced into the surface of the metal being tested. The relationship of load to the area or depth of indentation is the measure of hardness, such as in Brinell, Knoop, Rockwell, and Vickers hardness tests.Rebound tests: An object of standard mass and dimensions is bounced from the surface of the workpiece being tested, and the height of rebound is the measure of hardness. The Scleroscope and Leeb tests are examples.
Scratch file tests: The idea is that one material is capable of scratching another. The Mohs and file hardness tests are examples of this type.
Plowing tests: A blunt element (usually diamond) is moved across the surface of the workpiece being tested under controlled conditions of load and shape. The width of the groove is the measure of hardness. The Bierbaum test is an example.
Damping tests: Hardness is determined by the change in amplitude of a pendulum having a hard pivot, which rests on the surface of the workpiece being tested. The Herbert Pendulum test is an example.
Cutting tests: A sharp tool of given shape is caused to remove a chip of standard dimensions from the surface of the workpiece being tested.
Abrasion tests: A workpiece is loaded against a rotating disk, and the rate of wear is the measure of hardness.
Erosion tests: Sand or other granular abrasive is impinged on the surface of the workpiece being tested under standard conditions, and loss of material in a given time is the measure of hardness. Hardness of grinding wheels is measured by this testing method.
Electromagnetic testing: Hardness is measured as a variable against standards of known flux density.
Ultrasonic testing: A type of indentation test.
Chandler, Harry, ed.Hardness Testing Second Edition. 1999. Materials Park, OH. ASM International
Common Uses
Test Indenter Load Application Brinell 10-mm ball 3000 kg Cast iron and steel Brinell 10-mm ball 500 kg Nonferrous alloys Rockwell A Brale 60 kg Very hard materials Rockwell B 1/16-in. ball 100 kg Brass, low-strength steel Rockwell C Brale 150 kg High-strength steel Rockwell D Brale 100 kg High-strength steel Rockwell E 1/8-in. ball 100 kg Very soft materials Rockwell F 1/16-in. ball 60 kg Aluminum, soft materials Vickers Diamond pyramid 10 kg Hard materials Knoop Diamond pyramid 500 g All materials
Comparison of Indentation Hardness Tests
The minimum material thickness for a test usually is taken to be ten times the indentation depth.
Test
Indenter(s)
Indent Load(s) Method of Measurement Surface preparation Tests per hour Applications Remarks Diagonal or diameter Depth Brinell Ball indenter, 10 or 2.5 mm in diam 1-7 mm Up to 0.3 and 1 mm, respectively, with 2.5 and 10 mm diam balls 3000 kgf for ferrous materials down to 100 kgf for soft metals Measurement diam of indentation under microscope; read hardness from tables Specially grounded area for measurements of diam 50 with diam measurements Large forged and cast parts Damage to specimen minimized by use of lightly loaded ball indenter. Indent then less than Rockwell Rockwell 120° diamond cone, 1/16 - 1/2 in. diam ball 0.1-1.5 mm 25-375 µm Major 60-150 kgf Minor 10 kgf Read hardness directly from meter or digital display No preparation necessary on many surfaces 300 manually 900 automatically Forgings, castings, roughly machined parts Measure depth of penetration, not diam Rockwell superficial As for Rockwell 0.1-0.7 mm 10-110 µm Major 15-45 kgf Minor 3 kgf As for Rockwell Machined surface, ground As for Rockwell Critical surfaces of finished parts A surface test of case hardening and annealing Vickers 136° diamond pyramid Measure diagonal, not diam 0.03-0.1 mm 1-120 kgf Measure indent with low-power microscope; read hardness from tables Smooth, clean surface, symmetrical if not flat Up to 180 Fine finished surfaces, thin specimens Small indent, but high local stresses Microhardness 136° diamond indenter or a Knoop indenter 40 µm 1-4 µm min 1 gf-1 kgf Measure indentation with low-power microscope; read hardness from tables Polished surface Up to 60 Surface layers, thin stock down to 200 µm Laboratory test used on brittle materials or micro structural constituents Ultrasonic 136° diamond pyramid 15-50 µm 4-18 µm 800 gf Direct readout onto meter or digital display Surface better than 1.2 µm for accurate work. Otherwise, up to 3 µm 1200 (limited by speed at which operator can read display) Thin stock and finished surfaces in any position Calibration for Young's modulus necessary. 100% testing of finished parts. Completely nondestructive From Hardness Testing, 2rd Ed., by Harry Chandler, ASM International, 1999, p. 97.