Vickers hardness testing is a common and widely used method for determining the hardness of a material. It measures the depth of penetration of a diamond indenter under controlled conditions. Vickers hardness test charts are commonly used to monitor production and ensure quality control. This article discusses how you can represent and read the Vickers hardness scale.
I. Why Use the Vickers Hardness Value?
The Vickers hardness scale provides an excellent means to measure hardness in all materials, especially when compared with the Brinell test or Rockwell scale, which uses different indenters on the test piece. Unlike the other methods, the Vickers hardness test uses only one indenter and one test force to measure and inspect the hardness of a material. The diamond indenter used in the Vickers test can be used in any material, and the calculation of the Vickers hardness does not depend on the type of material. The Vickers method has a wider scale compared to other hardness testing methods. The Vickers method has standards for guidelines and conditions defined under ISO 6506-1 for metallic materials.
Related Article: ASTM Vickers Hardness Standard Test Reference Guide
II. How Vickers Hardness Gets Measured?
Vickers hardness testing is measured by inserting a diamond pyramid indenter into a test piece at a specific angle and measuring the force required to penetrate the tested material. The required force is directly related to the surface area of the indenter, and it is measured in units of kgf, which is represented as HV (Vickers Hardness).
Since Vickers hardness is based on the contact area between an indenter and the material being tested, it provides superior accuracy even when testing softer materials. The Vickers scale used in high-quality machines is optical, allowing you to measure small changes in surface hardness with precision.
Related Article: How to Perform a Vickers Hardness Test?
Related Article: How to Perform a Rockwell Hardness Test?
III. How do you Read a Vickers Hardness Value?
The Vickers hardness scale is made up of three main parts. These are a numeric number representing the Vickers hardness value, two abbreviation letters”HV” representing the “Hardness according to Vickers”, and the load applied to the test piece in kgf. If the load is applied for more than 15 seconds, the dwell time should be indicated following the ISO 6507 standards.
IV. Examples of How to Represent and Read Vickers Hardness Value
Example 1: 640 HV30
640 is the numeric value representing the Vickers hardness of the material.
HV is the abbreviation representing Vickers hardness
30 represents the load applied to the indenter. (a force of 294.2 N )
Example 2: 610 HV10/30
610 is the numeric value representing the Vickers hardness of the material.
HV is the abbreviation showing the Vickers hardness.
10 represents the load applied on the test piece. (a force of 98.07 N)
30 represents the dwell time that is outside the scope of 10 to 15 seconds.
V. What is the Vickers Hardness Number for Iron?
The Vickers hardness of iron is 30-80HV5. This suggests that the Vickers hardness number would range from 30 to 80 kgf/mm2 if the test had a load value of 5 kgf. The real value will vary depending on the iron specimen’s composition; this figure is only an estimate.
VI. What is the Vickers Hardness Number for Carbon Steel?
For carbon steel, the Vickers hardness ranges from 55 to 120HV5. The Vickers hardness number would fall between 55 and 120 kgf/mm2 if the test were conducted with a load value of 5 kgf. The value is an estimate, and it may change depending on the carbon steel composition.
Conclusion
The Vickers hardness test is a common, widely used method for measuring the hardness of materials. It is an excellent method when testing softer materials that could not withstand the forces required by other standards such as Brinell, Rockwell, or Mohs scale. Therefore, using the Vickers scale in mechanical testing is recommended when you need more accuracy and precision.