Hardness test is a mechanical property test that measures the surface hardness of solid materials. Common hardness tests include Brinell hardness, Rockwell hardness, and Vickers hardness.

1. Brinell hardness test

During the experiment, a steel ball with a diameter of D is pressed into the surface of the tested material with a certain load P of a certain size. After holding for a certain period of time, the load is removed and an indentation with a diameter of d is left on the surface. The surface area F of the indentation is calculated, and the Brinell hardness value is obtained according to the following formula, represented by HB. Reference standards include "Metallic Materials Brinell Hardness Test Part 1: Test Method" GB/T 231.1-2018, etc.

2. Rockwell hardness test

During the experiment, a diamond cone with a cone angle of 120 ° or a steel ball with a diameter of 1.588 mm is used as the indenter. The initial load P0 is first pressed into the surface of the tested part at a depth of h0. Then, the main load P1 is added, and the total load P=P0+P1. At this point, the total depth of pressing is h1. After removing the main load P1, the elastic deformation of the sample is restored to h2, so h=h1-h2-h0. The hardness value can be calculated from the h value according to the formula, where k is a constant. In fact, the HR value can be read directly on the dial without calculation on the Rockwell hardness tester. Reference standards include "Metallic Materials - Rockwell Hardness Test - Part 1: Test Methods" GB/T 230.1-2018, etc.

3. Vickers hardness test

Press two regular angular pyramids with a relative angle of 136 ° into the surface of the test piece under a certain load P. Calculate the surface area F of the indentation based on the average diagonal length d of the indentation, and the Vickers hardness value HV can be calculated by the relevant formula. The Vickers hardness value can also be obtained by referring to a table based on the length of the indentation diagonal and the load. Reference standards include "Metallic Materials Vickers Hardness Test Part 1: Test Method" GB/T 4340.1-2009, etc.

4. Leeb hardness test

The Leeb hardness test method is a dynamic hardness test method that uses a specified mass of impact body to vertically impact the surface of the specimen at a certain speed under the action of spring force. The Leeb hardness of the material is expressed by the ratio of the rebound speed of the impact body at a distance of 1mm from the surface of the specimen to the impact speed. Reference standards include GB/T 17394.1-2014 "Metallic Materials Leeb Hardness Test Part 1: Test Method" and others.

5. Knoop hardness test

Press the diamond indenter of the diamond pyramid with a specified angle on the opposite sides of the top two phases into the surface of the specimen with test force. After a specified holding time, remove the test force and measure the length of the diagonal of the indentation on the surface of the specimen. The Nusselt hardness is proportional to the quotient obtained by dividing the test force by the projected area of the indentation, and the indentation is considered to have a rhombohedral pyramid shape with the same angle as the top of the indenter. Reference standards include "Metallic Materials Knoop Hardness Test Part 1: Test Method" GB/T 18449.1-2009, etc.

6. Vickers hardness test

Press a steel indenter of a specified shape into the surface of the specimen under a certain test force, and use the depth of the indenter to represent the hardness of the material. The indentation depth of 0.0125mm is defined as one unit of Vickers hardness. The hardness of the material is related to the depth of pressing, with shallower pressing resulting in higher hardness and vice versa. Reference standards include GB/T 32660.1-2016 "Metallic Materials - Vickers Hardness Test Part 1: Test Method" and others.