Vickers Hardness Testing
The Vickers hardness test method, otherwise called a microhardness test method, is used for small objects, thin sections, as well as the case depth work. Due to the small indentation in a Vickers test, it can test very thin materials like foils, small parts, small areas, or the surface of a part, and individual microstructures. It can also figure out the depth of hardening by sectioning apart and creating a series of indentations to find the change in hardness. This method can evaluate almost any type of material such as ceramics, metals, and composites as well.
This testing method is based on an optical measurement system, which requires a range of light loads with the help of a diamond indenter to create an indentation. This indentation can then be measured and converted into a hardness value. It can evaluate a wide type of materials; however, test samples should be highly polished to help in evaluating the size of the impressions. Here, a square base pyramid shaped diamond is used for testing. The ‘Micro’ loads typically range from 10gm to 1kgf, while ‘Macro’ Vickers loads up to 30 kg or more.
Sectioning is required to deliver a small specimen that can fit in the tester. In addition to that, it is mandatory to make the specimen’s surface smooth by allowing the properly shaped indentation with the right measurement. This step ensures that the sample can be held perpendicularly to the indenter.
These prepared samples are mounted in a plastic medium to proceed with the preparation and testing. The indentations should be large enough to improve the measurement resolution. As the indentation size decreases, the error magnifies. This procedure is subjected to the problems of operator influence on the test outcome. For more information about Vickers hardness tester, contact us.
Vickers Hardness Testing Guide
Have you ever wondered why Vickers hardness testing is such an important method for testing material strength?
The hardness of a material can be critical to the application of that material in manufacturing other products. This is where the use of the Vickers hardness testing method comes into play. Aside from its many benefits, Vickers hardness test is a much easier method of measuring the hardness of a thin material sample. It is also one of the oldest and most widely adopted hardness testing techniques for welds and metals globally.
If you’d like to know more about this type of hardness testing method, then read on.
I. What is the Vickers Hardness Test?
Vickers hardness testing has been extensively employed as one of the rudimentary and authentic material testing techniques. The Vickers hardness test estimates the indentation hardness for a fractional part of metal, composites, or ceramic materials. In essence, the hardness of a material is its potential to present material with structural integrity and resistance to deformation after being exposed to continuous stress. Hence, the application of the Vickers hardness test. Furthermore, like the other hardness tests, the Vickers hardness test utilizes the Pyramid Number (HV) or the Diamond Pyramid Number (DPH) as its unit of hardness.
II. Why use the Vickers Hardness Test?
The Vickers hardness test method is used for the following reasons
- Universal Indentation – Due to the universal shape of the indenters of the Vickers hardness tester, it requires less calibration time. The deformative resistance of the diamond also means the indenters do not need replacement. Additionally, indentations are the same for all tests, therefore, correctional factors for particular materials are eliminated.
- Non-Destructive Procedure – The material tested is not damaged completely after the test, therefore it can be used for other purposes. Except for visible indentations, the Vickers hardness test intends to reduce the wastage of test samples.
- Application Range – The Vickers hardness test method is suitable for measuring both hard materials such as metal, as well as measuring softer materials like plastic.
III. Applications of Vickers Hardness Test
As a result of the relatively minimal indentation produced by the Vickers testing method, its usefulness is extremely important to hardness testing. Application of the Vickers hardness testing method has a wide range. And because of its scaling, it can measure hard samples such as steel, metal, and ceramics. It can also measure softer samples such as plastic. The Vickers testing method measures thin sample objects like the foil and also small sections of a test material.
IV. How to Measure Vickers Hardness?
Several conditions are to be observed before measurement occurs. And one of such conditions is to have a flat and smooth sample surface for accurate measurement and precise indentation. It must also be small enough to fit the scale. Additionally, indentations have to be large enough to attain a high measurement accuracy. When all these conditions are met, testing commences. And testing requires placing a sample on the tester, then the indenter makes contact with the sample material, the indenter is square-based and pyramid-shaped. The load when applied to the test sample pushes through the test sample and is allowed a dwell time of 10-15 seconds. When dwell time elapses, the load is removed, and the indenter is also released for the operator to measure via an optical estimation. The dimensions of indentation are calculated. However, the smaller the indentation, the higher the possibility of error and vice versa.
V. Limitations of Vickers Hardness Test
Despite all the benefits of the Vickers hardness test method, it has a few drawbacks as well. Some of these drawbacks include that whenever a sample material surface is precoated, the coating thickness may affect the accuracy of measurement. Secondly, it is observed that at lower loads, a level of irregularity sets in. Furthermore, in comparison with the Rockwell method, the Vickers method may take more time of up to 30-60 seconds to conduct tests. And this is not inclusive of the time taken to prepare the test environment. Lastly, the Vickers tester is much more expensive compared to the Rockwell tester as an optical evaluation will be necessary to complete the test.
To wrap this up, given the drawbacks of the Vickers hardness tester as regards the coating thickness, which is likely to affect measurements, nanotechnology advancements have been developed for nano-indentation methods which can be employed during testing. In addition, if all requirements for adopting the Vickers hardness testing procedures are accomplished, then it poses a better testing option compared to the other hardness testing techniques.
Finally, the Vickers hardness testing method has more application range. Therefore, you might want to consider employing the Vickers method for your next hardness testing.
Need Any Help?
You tell us what you want, and we tell you our solution.