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Macro vs Micro Hardness Testing: Basics, Advantages and Disadvantages, Applications

In this blog post, you’ll read:These hardness tests can be categorized as macro and micro. All hardness testing methods lie under these categories. In this article, we will discuss hardness types, advantages, disadvantages, and applications. These things are important to understand as they have many consequences on the mechanism of indentation in the hardness testing methods.

Table of Contents

Hardness is the character of the material that is important to measure while manufacturing any industrial items. The Brinell, Vickers, Rockwell, Shore, Knoop, and other hardness methods are applied to calculate hardness through an indentation at various scales but they all fall into two categories. 

These hardness tests can be categorized as macro and micro. All hardness testing methods lie under these categories. In this article, we will discuss hardness types, their advantages, disadvantages, and applications. These things are important to understand as they have many consequences on the mechanism of indentation in the hardness testing methods.

I. Macro Hardness

 

Micro Hardness Testing

 

1. What is Macro Hardness?

Macro hardness has another scientific name called macro indentation hardness testing. It is the measurement of the value of the hardness of the sample object with the application of heavy loads. Macro hardness is the easy and fast procedure to get data related to mechanical properties of bulk materials of the same category with the help of a small sample.

 

2. Theory and Principle of Macro Hardness Testing

Macro is another name for large, that’s why we can say that macro hardness is used when you need to apply heavy loads and large force. Macro hardness test tests are specified by indentations test forces or loads L. It calculates the resistance of the object with the penetration of a non-deformable indenter.

Macro hardness is of two types: regular or superficial. Regular macro hardness is an application of test when the surface area is large, and the indention is deep. Superficial macro hardness is applied with a large surface area, but penetration is shallow in this test.

 

3. Advantages and Disadvantages of Macro Hardness Testing

Advantages of Macro Hardness Testing

  • These tests are easy to perform and the process can be completed in less time
  • You can measure a wide range of hardness in these testing methods.
  • It provides you with more accurate and reliable results than micro hardness testing.
  • There is no need for any expensive optical devices.
  • It can measure rough surfaces also.

Disadvantages of Macro Hardness Testing

  • Macro hardness testing is not suitable for small objects due to large indentation
  • Sometimes results are a little inaccurate such as for  hard balls
  • These tests are calculated by a human so the chances of error are high

 

4. Applications of Macro Hardness Testing

Application of Macro hardness testing methods mostly includes measurement of rapid routine hardness tests. You can use macro hardness testing for materials with normal size. It can be used for quality check of surface treatment methods. The method can apply with the help of standard test forces and indenters. The load applied in macro hardness tests is of extensive range, starting from 50N to 30000N.

 

5. Macro-indentation Test Method

Macro indentation test methods are following, these are the tests with high loads, large deformation of areas, and very deep penetrations.

  • The Macro Rockwell hardness test

The Macro Rockwell hardness test is measured by the depth of the indentation when you apply load on the sample object. The application of such methods is used to analyze the value of relative resistance of the sample object against indentation. Objects can be various types of plastics.  

  • The Macro Brinell hardness test 

Macro Brinell hardness test measurement is calculated by the formula in which the applied test force (kilograms) is divided by the surface area of the developed indentation (square millimeters). The final value is called a  pressure measurement, but it has no unit.

  • The Macro Vickers hardness test 

It analyzes the hardness of the object by calculating the size of an impression caused by a diamond indenter. This type of hardness test is used for metals and ceramic materials. The test force or load used in the Vickers test is lighter than that of the Rockwell hardness test.

 

II. Micro Hardness

 

Macro vs Micro Hardness Testing

 

1. What is Micro Hardness?

Micro hardness testing also called micro indentation is a procedure of measuring the hardness of the material (metals, ceramics metals and composites) when the sample testing object is not large enough to perform a macro hardness test. In this scenario, the surface, where the test is going to perform, should be polished and smooth.

 

2. Theory and Principle of Micro Hardness

The principle of Micro Hardness Tests stands on static indentations caused by a test force of 1kgf. or less. Generally, the need for a metallographic finish becomes high as the applied force becomes small. A diamond indenter is used here for making an indentation with the help of a load. In such cases, while performing a test Microscopes are required for measuring the results. The hardness in the micro test is the mean of the stress of the object due to indentation.

 

3. Advantages and Disadvantages of Micro Hardness

Advantages of micro hardness

  • It can measure the hardness of thin layers
  • in the micro hardness test, only u one type of indenter is used
  • A MIcro hardness test can also utilize of Non-destructive tests

Disadvantages of micro hardness

  • It works for the minimum range hardness  only
  • you need optical devices such as a microscope to analyze the results
  • It is an expensive to process than the macro hardness test
  • The procedure of these tests is longer than others.

 

4. Applications of Micro Hardness

Micro hardness test is used for measuring the hardness of thin or small objects, complicated shapes, surface coatings, and plantings. This testing method can also perform for depth identification of case-hardened layers, carburization, grind burns, decarburization and also for surface contamination. Vickers and Knoop tests are the application of microhardness tests.

 

5. Micro-indentation Tests

Micro Vickers and Knoop hardness tests whose indentation is less than 1kgf are standardized by ASTM E 384.

  • Knoop hardness test

In the Knoop microhardness test a controlled force of 1000 grams or less is applied for some specific time to a rhombus-shaped pyramid indenter. Then the hardness is evaluated by the depth caused by the penetration of the indenter. The outcome can be measured through a microscope.

  • Vickers hardness test

The Vickers hardness test can be a macro or micro hardness test as it can bear a load up to 50 kg. The process of the Vicker hardness test is the same as the Knoop test but the indenter used hare is a square-based diamond pyramid indenter. 

 

Conclusion

Micro hardness testing method and Macro hardness testing method are the main two types of hardness tests under which all other methods lie, that’s why it is important to understand these two terms. In this article, we have completely defined two terms and which methods fall in which category. Still, if you want to know more about the micro or macro test or other types of tests then visit our website or explore our products.