Vicker's Hardness Test
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Experiment # 1 Objective Measurement of Hardness by using Micro or Vicker’s Hardness Test
Abstract Micro Vickers Hardness Tester adopts LCD screen to display. By mean of control keys, HV or HK hardness scales, testing force and duration time can be selected and brightness of light source can be adjusted without steps. With measuring microscope, it may test out the length values of diagonals D1and D2, and then press the keys to input the length values, and the hardness values will be displayed on the LCD screen. Operation is easy. The aim of this paper is to present our experience on determining the case depth in mechanical equipment and machinery tools of carburized parts providing information on its mechanical properties.
Theory (1) To understand what hardness is, and how it can be used to indicate some properties of materials (2) To conduct typical engineering hardness tests and be able to recognize commonly used hardness scales and numbers (3) To be able to understand the correlation between hardness numbers and the properties of materials (4) To learn the advantages and limitations of the Vicker’s Hardness Test. Experimental Condition: Temperature: 25oC Introduction It is a common practice to test most materials before they are accepted for processing, and before they are put into service to determine whether or not they meet the specifications required. One of these tests is hardness.
What is Hardness? Hardness has typically been defined as the resistance of a material to permanent penetration by another one that is harder. This can be achieved by using an intender with hardness similar to
that of the diamond. In combination with the applied force on it and the velocity of the application and finally the total time of the penetration applied.
Hardness Measurement Method There are three types of tests used with accuracy by the metals industry; they are the Rockwell hardness test, the Brinell hardness test, and the Vickers hardness test. The way the three of these hardness tests measure a metal's hardness is to determine the metal's resistance to the penetration of a non-deformable ball or cone. The tests determine the depth or area which such a ball or cone will sink into the metal, under a load, within a specific period of time. The followings are the most common hardness test methods used in today`s technology: 1. Rockwell hardness test Hardness Test 2. Brinell hardness
3.
Vickers/Micro
4. Knoop hardness
Vicker’s/Micro Hardness Test A method of determining the hardness of steel whereby a diamond pyramid is pressed into the polished surface of the specimen and the diagonals of the impression are measured with a microscope fitted with a micrometer eye piece. The rate of application and duration are automatically controlled and the load can be varied. Two types of indenters are generally used for the Vickers test family, a square base pyramid shaped diamond for testing in a Vickers hardness tester and a narrow rhombus shaped indenter for a Knoop hardness test.
Usage Range Heat treated layer, carbonized layer, hardened hard layers, superficial coating, steels, non-ferrous metal, micro and thin shaped components.
Standards Vickers test methods are defined in the following standards: •
ASTM E384 – micro force ranges – 10g to 1kg
•
ASTM E92 – macro force ranges - 1kg to 100kg
•
ISO 6507-1,2,3 – micro and macro ranges
Features AUTO TURRET
Auto Turret performs a series of load operations and object lens for measuring comes automatically back to the central position after making indentation. Positive turret stops ensure exact alignment of the indenter to the measuring and scanning objectives. This allows precise replacement of the diamond impression on your test sample.
Main Menu display
LIQUID CRYSTAL DISPLAY TOUCH—PANEL
Loaded with a LCD display with backlight. The hardness tester secures very clear and high visibility. REPUTED LOADING MECHANISM
Loading mechanism with to fluctuation, “capable to hit aimed portion”, is highly evaluated. HK KNOOP HARDNESS
Knoop hardness calculating functions can be changed over with
Measuring Data Display
a one-touch panel operation. (HK diamond indenter is optional) TWO OBJECT LENSES CAN BE MOUNTED
SIMULTANEOUSLY In additional to the normal measuring lens (x10 or x20), one more lens of different magnification can be mounted regularly. (Additional lens is optional) HIGH RIGIDITY BODY
Newly designed VMT-7 (7S) can perform high-accuracy measurements with the especially rigidity enhanced body. APPLICABLE TO CE AND SAFETY
Overall Data Display
Safety design applicable to EU low voltage command, EMC command. In addition to highrigidity body, overturn-preventive metal fittings are attached as standard to prevent overturning by earthquakes etc.
Vicker’s Test Method The principle of the Vickers Hardness method is similar to the Brinell test The Vickers indenter is a 136 degrees square-based diamond pyramid. The indenter is pressed into the sample by an accurately controlled test force of 1 to 120 kgf. The force is maintained for a specific dwell time, normally 10 – 15 After the dwell time is complete, the indenter is removed leaving an indent in the sample that appears square shaped on the surface. The impression, produced by the Vickers indenter is clearer, than the impression of Brinell indenter; therefore this method is more accurate. The size of the indent is determined optically by measuring the two diagonals of the square indent and their average is calculated.The length of the impression diagonal is measured by means of a microscope, which is usually an integral part of the Vickers Tester. The load, varying from 1kgf to 120 kgf, is usually applied for 30 seconds.
The Vickers number (HV) is calculated by the formula:
Principle of Vicker's Hardness Testing
HV = 1.854*F/ D² Where F- Applied load, kg D – Length of the impression diagonal, mm The Vickers number, which normally ranges from HV 100 to HV1000 for metals, will increase as the sample gets harder. Tables are available to make the calculation simple, while all digital test instruments do it automatically.
Designations The labeling for Vickers tests is HV (H= hardness, V = Vickers), then the test load and the test time. The test load is indicated in the usual kgf numerical values. That is why the actual test load must be divided by 9.81 to get the Vickers label (e.g. HV50: 50 = 490.5N / 9.81). Thus, a Vickers hardness value might look as follows: 210 HV50/30 Vickers hardness 210, test load 490.5N, test time 30 seconds
Technical Specifications
Testing Force
10g (0.098N)、25g (0.245N)、50g (0.49N)、100g (0.98N)、200g (1.96N)、300g (2.94N)、500g (4.9N)、1000g (9.8N)
Min Measuring Unit
0.5μm
Magnification of Microscope
100X For Observation ,400X For Measurement
Loading Method
Automatically (load, keep, unload)
Overall Dimension
405×290×480mm
Net Weight
25kg
Max Height of Specimen
65mm
Power Supply
AC220V±5%,50~60Hz
X-Y Testing Table
Dimension: 100×100 mm. Max. Travel Range: 25×25mm
Standard Accessories
Objectives 40x and 10x, Vickers Indenter, Microscope 10x, Standard
Application •
Because of the wide test force range, the Vickers test can be used on almost any metallic material. The part size is only limited by the testing instrument's capacity.
•
For instance, when a material is tested with a test load of 294.30N and then a second time with 9.81N the results are the same (of course, only if the material is homogeneous and without layers of different hardness values).
•
The Vickers method is also suitable for materials with different layers. Increasing test loads are applied subsequently to determine the thickness of certain surface layers, e.g. after nitration hardening.
•
Apart from that, all the rules mentioned above for the other methods (minimum thickness = 10 x indentation depth) also apply to Vickers. In other words, the diagonal must not be longer than 2/3 of the specimen thickness.
•
The Vickers method is especially suitable for tests of small and thin parts or components with any kind of surface treatment, i.e. for tests with low test loads. However, the Vickers method should not be used for inhomogeneous materials, like cast iron.
Strengths •
One scale covers the entire hardness range.
•
A wide range of test forces to suit every application.
•
Nondestructive, sample can normally be used.
Weaknesses •
The main drawback of the Vickers test is the need to optically measure the indent size. This requires that the test point be highly finished to be able to see the indent well enough to make an accurate measurement.
•
Slow. Testing can take 30 seconds not counting the sample preparation time.
Advantages/Features •
Two variants are available: •
Analogue tester 3212001 with evaluation via the enclosed hardness tables
•
PC Tester 3212003 with automatic evaluation (indentation measurement on a PC monitor)
•
Flexible test area height, can be swiveled by 180°
•
Microscope with a series revolver head for up to 4 objective lenses
•
Different objective lenses for a wide range of magnifications and picture ranges
•
The PC model works in conjunction with the test software testXpert®. This software is highlighted especially by its simple operation and adaption to changing test conditions
•
Manual or motorized moving compound table variants are available
•
Prisms, clamping devices and parallel vice are optional extras.
Comments: •
The biggest advantage of Vickers is its scale, which comprises the smallest and the highest hardness values in one scale. It is thus very suitable for laboratory tests.
•
Most of the disadvantages of Vickers are based on the long duration of the whole procedure because the indentation must be measured optically (with the help of a microscope or projector). This, of course, also is a source for measuring errors. However, modern, automatic image evaluation computer systems reduce this source of errors
significantly •
The surface must be well prepared and the penetrator must be applied evenly. Otherwise, the smallest inclination would cause irregularities in the indentation. Thus, the Vickers procedure is not suitable for routine tests.
•
The indentation is not well readable on some materials because of the irregular distribution of the load (more load on the edges than on the sides of the pyramid).
References 1. http://www.ukcalibrations.co.uk/vickers_htm.html 2. http://wapedia.mobi/en/Vickers_hardness_test 3. http://www.instron.co.uk 4. http://www.pdfcoke.com/doc/18004150/Hardness-Report?autodown=pdf 5. “Technical Metallurgy” by Cliffe (page 150 – 154) 6. “Material, Their Nature, Fabrication and Properties” by Sergal (page 143 – 145, 71 –72) 7. “Metallurgy for Engineers” by Rollesan (page 15)
Abstract Micro Vickers Hardness Tester adopts LCD screen to display. By mean of control keys, HV or HK hardness scales, testing force and duration time can be selected and brightness of light source can be adjusted without steps. With measuring microscope, it may test out the length values of diagonals D1and D2, and then press the keys to input the length values, and the hardness values will be displayed on the LCD screen. Operation is easy. The aim of this paper is to present our experience on determining the case depth in mechanical equipment and machinery tools of carburized parts providing information on its mechanical properties.
Theory (1) To understand what hardness is, and how it can be used to indicate some properties of materials (2) To conduct typical engineering hardness tests and be able to recognize commonly used hardness scales and numbers (3) To be able to understand the correlation between hardness numbers and the properties of materials (4) To learn the advantages and limitations of the Vicker’s Hardness Test. Experimental Condition: Temperature: 25oC Introduction It is a common practice to test most materials before they are accepted for processing, and before they are put into service to determine whether or not they meet the specifications required. One of these tests is hardness.
What is Hardness? Hardness has typically been defined as the resistance of a material to permanent penetration by another one that is harder. This can be achieved by using an intender with hardness similar to
that of the diamond. In combination with the applied force on it and the velocity of the application and finally the total time of the penetration applied.
Hardness Measurement Method There are three types of tests used with accuracy by the metals industry; they are the Rockwell hardness test, the Brinell hardness test, and the Vickers hardness test. The way the three of these hardness tests measure a metal's hardness is to determine the metal's resistance to the penetration of a non-deformable ball or cone. The tests determine the depth or area which such a ball or cone will sink into the metal, under a load, within a specific period of time. The followings are the most common hardness test methods used in today`s technology: 1. Rockwell hardness test Hardness Test 2. Brinell hardness
3.
Vickers/Micro
4. Knoop hardness
Vicker’s/Micro Hardness Test A method of determining the hardness of steel whereby a diamond pyramid is pressed into the polished surface of the specimen and the diagonals of the impression are measured with a microscope fitted with a micrometer eye piece. The rate of application and duration are automatically controlled and the load can be varied. Two types of indenters are generally used for the Vickers test family, a square base pyramid shaped diamond for testing in a Vickers hardness tester and a narrow rhombus shaped indenter for a Knoop hardness test.
Usage Range Heat treated layer, carbonized layer, hardened hard layers, superficial coating, steels, non-ferrous metal, micro and thin shaped components.
Standards Vickers test methods are defined in the following standards: •
ASTM E384 – micro force ranges – 10g to 1kg
•
ASTM E92 – macro force ranges - 1kg to 100kg
•
ISO 6507-1,2,3 – micro and macro ranges
Features AUTO TURRET
Auto Turret performs a series of load operations and object lens for measuring comes automatically back to the central position after making indentation. Positive turret stops ensure exact alignment of the indenter to the measuring and scanning objectives. This allows precise replacement of the diamond impression on your test sample.
Main Menu display
LIQUID CRYSTAL DISPLAY TOUCH—PANEL
Loaded with a LCD display with backlight. The hardness tester secures very clear and high visibility. REPUTED LOADING MECHANISM
Loading mechanism with to fluctuation, “capable to hit aimed portion”, is highly evaluated. HK KNOOP HARDNESS
Knoop hardness calculating functions can be changed over with
Measuring Data Display
a one-touch panel operation. (HK diamond indenter is optional) TWO OBJECT LENSES CAN BE MOUNTED
SIMULTANEOUSLY In additional to the normal measuring lens (x10 or x20), one more lens of different magnification can be mounted regularly. (Additional lens is optional) HIGH RIGIDITY BODY
Newly designed VMT-7 (7S) can perform high-accuracy measurements with the especially rigidity enhanced body. APPLICABLE TO CE AND SAFETY
Overall Data Display
Safety design applicable to EU low voltage command, EMC command. In addition to highrigidity body, overturn-preventive metal fittings are attached as standard to prevent overturning by earthquakes etc.
Vicker’s Test Method The principle of the Vickers Hardness method is similar to the Brinell test The Vickers indenter is a 136 degrees square-based diamond pyramid. The indenter is pressed into the sample by an accurately controlled test force of 1 to 120 kgf. The force is maintained for a specific dwell time, normally 10 – 15 After the dwell time is complete, the indenter is removed leaving an indent in the sample that appears square shaped on the surface. The impression, produced by the Vickers indenter is clearer, than the impression of Brinell indenter; therefore this method is more accurate. The size of the indent is determined optically by measuring the two diagonals of the square indent and their average is calculated.The length of the impression diagonal is measured by means of a microscope, which is usually an integral part of the Vickers Tester. The load, varying from 1kgf to 120 kgf, is usually applied for 30 seconds.
The Vickers number (HV) is calculated by the formula:
Principle of Vicker's Hardness Testing
HV = 1.854*F/ D² Where F- Applied load, kg D – Length of the impression diagonal, mm The Vickers number, which normally ranges from HV 100 to HV1000 for metals, will increase as the sample gets harder. Tables are available to make the calculation simple, while all digital test instruments do it automatically.
Designations The labeling for Vickers tests is HV (H= hardness, V = Vickers), then the test load and the test time. The test load is indicated in the usual kgf numerical values. That is why the actual test load must be divided by 9.81 to get the Vickers label (e.g. HV50: 50 = 490.5N / 9.81). Thus, a Vickers hardness value might look as follows: 210 HV50/30 Vickers hardness 210, test load 490.5N, test time 30 seconds
Technical Specifications
Testing Force
10g (0.098N)、25g (0.245N)、50g (0.49N)、100g (0.98N)、200g (1.96N)、300g (2.94N)、500g (4.9N)、1000g (9.8N)
Min Measuring Unit
0.5μm
Magnification of Microscope
100X For Observation ,400X For Measurement
Loading Method
Automatically (load, keep, unload)
Overall Dimension
405×290×480mm
Net Weight
25kg
Max Height of Specimen
65mm
Power Supply
AC220V±5%,50~60Hz
X-Y Testing Table
Dimension: 100×100 mm. Max. Travel Range: 25×25mm
Standard Accessories
Objectives 40x and 10x, Vickers Indenter, Microscope 10x, Standard
Application •
Because of the wide test force range, the Vickers test can be used on almost any metallic material. The part size is only limited by the testing instrument's capacity.
•
For instance, when a material is tested with a test load of 294.30N and then a second time with 9.81N the results are the same (of course, only if the material is homogeneous and without layers of different hardness values).
•
The Vickers method is also suitable for materials with different layers. Increasing test loads are applied subsequently to determine the thickness of certain surface layers, e.g. after nitration hardening.
•
Apart from that, all the rules mentioned above for the other methods (minimum thickness = 10 x indentation depth) also apply to Vickers. In other words, the diagonal must not be longer than 2/3 of the specimen thickness.
•
The Vickers method is especially suitable for tests of small and thin parts or components with any kind of surface treatment, i.e. for tests with low test loads. However, the Vickers method should not be used for inhomogeneous materials, like cast iron.
Strengths •
One scale covers the entire hardness range.
•
A wide range of test forces to suit every application.
•
Nondestructive, sample can normally be used.
Weaknesses •
The main drawback of the Vickers test is the need to optically measure the indent size. This requires that the test point be highly finished to be able to see the indent well enough to make an accurate measurement.
•
Slow. Testing can take 30 seconds not counting the sample preparation time.
Advantages/Features •
Two variants are available: •
Analogue tester 3212001 with evaluation via the enclosed hardness tables
•
PC Tester 3212003 with automatic evaluation (indentation measurement on a PC monitor)
•
Flexible test area height, can be swiveled by 180°
•
Microscope with a series revolver head for up to 4 objective lenses
•
Different objective lenses for a wide range of magnifications and picture ranges
•
The PC model works in conjunction with the test software testXpert®. This software is highlighted especially by its simple operation and adaption to changing test conditions
•
Manual or motorized moving compound table variants are available
•
Prisms, clamping devices and parallel vice are optional extras.
Comments: •
The biggest advantage of Vickers is its scale, which comprises the smallest and the highest hardness values in one scale. It is thus very suitable for laboratory tests.
•
Most of the disadvantages of Vickers are based on the long duration of the whole procedure because the indentation must be measured optically (with the help of a microscope or projector). This, of course, also is a source for measuring errors. However, modern, automatic image evaluation computer systems reduce this source of errors
significantly •
The surface must be well prepared and the penetrator must be applied evenly. Otherwise, the smallest inclination would cause irregularities in the indentation. Thus, the Vickers procedure is not suitable for routine tests.
•
The indentation is not well readable on some materials because of the irregular distribution of the load (more load on the edges than on the sides of the pyramid).
References 1. http://www.ukcalibrations.co.uk/vickers_htm.html 2. http://wapedia.mobi/en/Vickers_hardness_test 3. http://www.instron.co.uk 4. http://www.pdfcoke.com/doc/18004150/Hardness-Report?autodown=pdf 5. “Technical Metallurgy” by Cliffe (page 150 – 154) 6. “Material, Their Nature, Fabrication and Properties” by Sergal (page 143 – 145, 71 –72) 7. “Metallurgy for Engineers” by Rollesan (page 15)
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