Vicker hardness

Vickers hardness test Vickers hardness tests Vicor Vicryl... 

Rockwell Hardness and Rockwell Superficial Hardness of Metallic Materials Test Method for Vickers Hardness of Metallic Materials Test Method Microhardness of Materials... 

Test Method for Vickers Hardness of MetaUic Materials... 

Vickers Hardness. The Vickers or diamond pyramid hardness (DPH) developed in 1924 was an improvement over the Brinell test. The Vickers test used a pyramidal diamond as the indenter. This permitted the hardness testing of much harder materials, and the constant 136° angle of the indenter eliminated the problem of variable indentation shape encountered using spherical indenters (1). 

Vickers hardness numbers are calculated from measurement of the indentation diagonals as follows, where HV = Vickers hardness,... 

The Vickers hardness test is a macrohardness test in which loads are commonly varied from 9.8 to 1180 N (1 to 120 kgf). Vickers hardness numbers are invariant with load within the stated limits. 

The Vickers hardness test is commonly made on a flat specimen on which the indenter is hydrauhcaHy loaded. When the desired number of indentations have been made, the specimen is removed and both diagonals of the indentations, measured using a caUbrated microscope, are then averaged. The Vickers hardness number may be calculated, or for standard loads taken from a precalculated table of indentation size vs VHN. The preferred procedures are described in ASTM E92 (2). 

The Vickers hardness test, developed in the United Kingdom, is more popular there than in the United States. VHN (Vickers hardness number) and DPH (diamond pyramid hardness) are synonymous terms. 

Fig. 3. Flame hardening (a) tempeiatuie—time heating curves of a 25 x 50 x 100 mm specimen at a feed of 75 mm /min and burner distance of 8 mm showing temperatures of A, surface B, 2 mm below surface and C, 10 mm below surface (b) hardness—depth curves for a 0.50% C steel 25 X 75 X 100 mm specimen at a feed of 50 mm /min, temperatures ia °C measured 10 mm below the surface, and burner distances ia mm, respectively, of A, 530 and 50 B, 540 and 12 C, 545 and 10 D, 550 and 8 and E, 565 and 6. Flame heating followed by water spray quenching. HV = Vickers hardness.

Eig. 8. Illustration of the effect of nitriding on the wear resistance of a steel blasted with steel grit A, 300 HV steel B, 750 HV steel case hardened by carburizing and C, 1100 HV steel nitrided at 500°C for 60 h (17). HV = Vickers hardness. 

The surface may gain a very high (eg, 1000 Vickers) hardness from this process. Surface deformation also produces a desired high compressive residual stress. Figure 9 illustrates the improvement in fatigue properties of a carburized surface that has been peened (18). 

Hardness. The Knoop indentation hardness of vitreous sihca is in the range of 473—593 kg/mm and the diamond pyramidal (Vickers) hardness is in the range of 600—750 kg/mm (1 4). The Vickers hardness for fused quartz decreases with increasing temperature but suddenly decreases at approximately 70°C. In addition, a small positive discontinuity occurs at 570°C, which may result from a memory of quartz stmcture (165). A maximum at 570°C is attributed to the presence of small amounts of quartz microcrystals (166). Scanning electron microscopic (sem) examination of the indentation area indicates that deformation is mainly from material compaction. There is htfle evidence of shear flow (167). 

Hardness is determined by measuring the penetration (depth or area) when a harder material, such as diamond, is pushed into the surface of the material of interest under a specified load. Tme hardness is defined as the force divided by the projected area. Vickers hardness tests, which employ a pyramid-shaped indentor, are frequently used to characterize ceramics however, Vickers hardness calculations normally employ total surface area rather than projected area (43). Measurements are made on the diamond impression shown in Figure 6. Vickers hardness is calculated using... 

Gold cast Yield strength, MPa Minimum elongation, % Vickers hardness, HV... 

Appleton and Waddington [40] present experimental evidence that pulse duration also affects residual strength in OFHC copper. Samples shock loaded to 5 GPa for 1.2 ps pulse duration exhibit poorly developed dislocation cell structure with easily resolvable individual dislocations. When the pulse duration is increased to 2.2 ps (still at 5 GPa peak stress) recovered samples show an increase in Vickers hardness [41] and postshock electron micrographs show a well-developed cell structure more like samples shock loaded to 10 GPa (1.2 ps). In the following paragraphs we give several additional examples of how pulse duration affects material hardness. 

This consists of loading a pointed diamond or a hardened steel ball and pressing it into the surface of the material to be examined. The further into the material the indenter (as it is called) sinks, the softer is the material and the lower its yield strength. The true hardness is defined as the load (F) divided by the projected area of the indent, A. (The Vickers hardness, H , unfortunately was, and still is, defined as F divided by the total surface area of the indent. Tables are available to relate H to Ff .)... 

Annealing temperature rcj Vickers hardness Time at annealing temperature (minutes)... 

Material Type and condition Typical standard for implant application Ultimate tensile strength M Pa min 0.2% tensile yield stress M Pa Young s modulus X lO M Pa Elongation at fracture % min Compressive strength M Pa Vickers hardness Fatigue strength (10 cycles) M Pa... 

Alloy Density (g/cm ) Melting pt. (liquidus, °C) Coefficient of expansion X lO Electrical conductivity % I.A.C.S. Thermal conductivity (W/m°K) Tensile strength (MN/m ) Elongation % Vickers hardness... 

Brinell hardness number Vickers hardness number hour... 

The Vickers hardness measurement uses a square based pyramid of about 100 pm height as the indenter. The included angles between opposite faces are a = 136°. This corresponds to the tangential angle of an ideal ball impression, considered to have a diameter equal to 0.375 times that of the ball1 . The hardness value is equal to the applied force P in newtons divided by the actual area of impression in mm2. 

Van der Waals solid 123 Vapour transport 201 Vickers hardness 122 Viscoelastic 203... 

Vickers Hardness 26.1 GPa Modulus of Elasticity 350-510 GPa Shear Modulus 193 GPa Bulk Modulus 241 GPa Poisson s Ratio 0.18... 

Vickers Hardness 19.65 GPa Modulus of Elasticity 338-580 GPa Shear Modulus 214 GPa Bulk Modulus 296 GPa Poisson s Ratio 0.21... 

Vickers Hardness (GPa) 24.5 - 28.2 (varies with crystal face) Modulus of Elasticity (GPa) 475 293K... 

Vickers Hardness 28-35 GPa Modulus of Elasticity 410-510 GPa Shear Modulus 186 GPa Bulk Modulus 240-390 GPa Poisson s Ratio 0.191... 

Vickers Hardness 22 GPa (as opposed to other carbides, the hardness is maintained at high temperature with little change. 

Vickers Hardness 12 GPa Young s Modulus 315 GPa Flexural Strength 390-490 MPa Poisson s Ratio 0.25 Flexural Strength 590-970 MPa Compressive Strength 2070 MPa... 

Vickers Hardness 18.73 GPa Young s Modulus 378 GPa Flexural Strength 421 MPa Compressive Strength 3455 MPa... 

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