Principle of microhardness test

The principle of micro hardness testing

Microhardness testing is a form of microscopy used to measure the hardness of a material. It uses a tester that measures a material’s mechanical properties, such as its ability to resist scratching or gouging, and to deform under pressure. Using a specialized testing instrument, a test specimen is placed under increasing pressure until it breaks or deforms, and then the load is measured. The hardness of a material is then interpreted according to the load it can tolerate.

The earliest known hardness testing method involved the use of a hammer and an anvil to hammer the test specimen against. It was the only method available until microscopic methods were developed. Now, microhardness testing is used in a variety of industries, including automotive manufacturing, aerospace, medicine, and research. The method is also used to evaluate the durability and performance of materials used in industries such as petrochemicals, electronics, and semiconductors.

The test equipment used for microhardness testing includes a Vickers tester, a Brinell-Ohler tester, and a Rockwell tester, all of which use specialized microscopes to measure the indentation of a specimen under controlled pressure. The Vickers tester uses a diamond-tipped plunger loaded with a load, while the Brinell-Ohler tester uses a cone-shaped head loaded with a certain amount of load. The Rockwell tester uses a diamond-tipped apparatus that is loaded with a certain load and then pressed into the specimen. The rockwell tester usually has a microhardness range of 1 to 100, while the others measure the indentation in terms of Vickers or Brinell-Ohler hardness.

The hardness of a material is determined by the amount of pressure it can withstand without permanent indentation. This is known as the yield point, which is the point at which a material will break or deform due to compression. Any further compression below this point is considered to be elastic, and the indention will rebound once the pressure is released.

The microhardness testing results determine the mechanical properties of the material being tested. These properties can be used to identify the material’s suitability for use in a specific application, as well as its strength relative to other materials. This method is preferred over other measures of hardness, such as shore hardness, because it is more precise and allows for easier comparison between different materials.

When performing microhardness testing, the test specimen must be clean and free of any contaminants, such as dirt and oil. The size of the test specimen should also be taken into consideration, as it can affect the results. The specimen should be large enough so that indentations can be accurately measured. If a specimen is too small, the indentations may not be properly measured and the results may be inaccurate. Furthermore, care should be taken not to damage the specimen during the test, as this can also lead to inaccurate results.

Microhardness testing is an essential method of evaluating the mechanical properties of materials, and is used in various industries and applications. This technique is highly precise and can be used to compare the hardness of different materials. The results can be used to identify materials suitable for specific applications, as well as evaluate the relative strength of materials. By understanding the principles of microhardness testing, professionals in a wide variety of fields can obtain the most accurate results and make reliable decisions about the materials available for their particular project.

microhardness testing is divided into macrohardness testing, microhardness testing, and nanohardness testing according to the scale of indentation performance. It is mainly used to test the hardness and hardness of heat-treated objects such as steel and alloys, thin-walled parts, thin plates, hardened layers, surface layers, nitriding layer and brazing layer in production.

The common principle of microhardness test is as follows: according to the analysis of the surface deformation of various materials under different load impact, the material with good contact deformation and fewer hard surface cracks is considered to be harder than the material with poor contact deformation and more hard surface cracks. According to the depth of the indentation on the surface of the object and the length of the edge of the indentation, the hardness of the object can be very roughly estimated.

In the actual microhardness test, the test force F is applied to the surface to be tested by means of a diamond or a diamond-tipped indenter. According to the size of the maximum test force, the test force is usually in the range of 1~1000gf. After the application of the test force, the size of the indenter will leave an impression on the surface, and then the size of the impressed indentation can be measured, including the indentation length l, the trace width of the impression b and the depth h of the indentation.

Therefore, the hardness of the test object can be obtained by calculating the ratio of the test force F, the indentation length l, the indentation width b and the indentation depth h. This is the working principle of microhardness test. Through such testing, product testing and quality assurance can be achieved.