A method that can be used for figuring out a material’s hardness—a measurement of its resistance to deformation in the presence of force—is the Vickers hardness test. While it finds use in other materials like ceramics & some polymers, this test is widely employed in the metallurgical area. The Vickers test is widely recognised because of its precision & versatility in handling various materials.
What is Hardness?
Before delving into the specifics of the Vickers hardness test, it’s important to understand what hardness means in the context of materials science. Hardness refers to a material’s resistance to permanent shape change when a compressive force is applied. In simpler terms, it measures how resistant a material is to being scratched, bent, or indented. There are several hardness tests available, each designed for specific types of materials & applications, & among them is the Vickers hardness test.
Introduction to the Vickers Hardness Test
Developed in 1921 by Smith & Sandl & Co. at Vickers Ltd., a British engineering conglomerate, It was initially designed to address the need for a method to measure materials of varying hardness. This test is known for its wide applicability, from soft metals like lead to the hardest, such as tempered steel & ceramics.
How the Vickers Test Works
It involves pressing a small, diamond-shaped tool, known as a Vickers pyramid, into the material’s surface with a specific, standardized force. The diamond indenter is square-based & pyramid-shaped, with an angle of 136 degrees between opposite faces. This indenter is pressed into the material under test with a predetermined force, held for a specific duration, & then removed.
After the indentation is made, the test material is examined under a microscope. The length of the diagonals of the indentation left by the diamond is measured, & these measurements are used to calculate the hardness value. Unlike other hardness tests, the Vickers test is known for the minimal material deformation it causes, making it suitable for precision parts.
Calculation of Hardness
The Vickers hardness number (VHN) or hardness value, is calculated using the formula:
HV = d 2 2Fsin(θ/2)
where:
F is the applied force in kilograms.
θ is the angle at the top of the diamond indenter (136 degrees). 10–15
d is the average length of the indentation diagonals in millimeters.
This formula essentially calculates the hardness by assessing the area of the indentation & the force applied.
Advantages of the Vickers Hardness Test
The Vickers hardness test is esteemed for several reasons:
Versatility: It can be used for all metals, unlike some tests that are limited to specific types or hardness ranges.
Precision: The test can target very small parts or thin materials with minimal surface damage.
Consistency: Provides highly reproducible results across different types of materials.
Gradation: Suitable for a wide range of hardness, from soft to very hard materials.
Procedure for Conducting the Vickers Hardness Test
To conduct a hardness test, the following steps are generally followed:
Sample Preparation: The material sample should be smooth & flat. Surface preparation might involve polishing to ensure accurate measurement.
Setting the Testing Machine: The Hardness Testing Machine is configured in accordance with the test’s particular specifications. As part of this, the proper load must be established.
Indentation: The sample is subjected to the diamond indenter. For a set amount of time, the load is maintained (usually 10–15 seconds).
Measurement: Post-indentation, the sample is examined under a microscope, & the lengths of the diagonals of the indentation mark are measured.
Calculation: Using the diagonal measurements, the Vickers hardness number is calculated.
Applications of the Vickers Hardness Test
The Vickers hardness test is used across various industries for different applications.
Metallurgy: To determine the hardness of metals & their alloys.
Manufacturing: In quality control, to ensure components meet the required hardness specifications.
Ceramics: To test the hardness of ceramic materials.
Research & Development: Used in material science research to compare the hardness of materials under different conditions.
Conclusion
In material science, the Vickers hardness test stands out as an exceptionally reliable & flexible method for assessing the hardness of a diverse array of materials. This technique is crucial not only in aerospace but also in manufacturing small, precision-engineered components, offering precise measurements across different material types. As material technologies advance, understanding how this test functions & its applications is vital. It helps researchers & engineers develop products that meet rigorous standards for quality & durability, thereby ensuring the Vickers hardness test remains indispensable for providing detailed insights into material properties & performance.
Infinita Lab further enhances this utility by offering a comprehensive catalog of 2000 material science tests, including the Vickers hardness test. With a network of accredited testing laboratories spread across the United States & offices in 16 strategic locations, Infinita Lab caters to a broad spectrum of industries. The company’s services are designed to simplify the testing process for businesses, featuring doorstep sample pickup & delivery. Infinita Lab’s team of top-tier expert consultants is available to assist clients in interpreting testing reports, making the technical details accessible & actionable.
What is a Vickers Hardness Test?
