Understanding Material Hardness: A Comprehensive Exploration of Testing Methods and Applications

Hardness is a mechanical property that measures the resistance of a material to deformation and scratching, determined through hardness tests. There are two main types of hardness tests: indentation methods and scratch methods. Indentation methods include static load indentation and dynamic load indentation (rebound method). Static load indentation methods include Brinell hardness, Rockwell hardness, Vickers hardness, and microhardness, each characterized by different loads, indenters, and measurement techniques.

The physical significance of hardness values varies depending on the test method. Hardness values obtained through indentation methods indicate the material's ability to resist plastic deformation when pressed by another object. Values obtained through scratch methods represent the material's resistance to local surface fracture, while rebound method values indicate the magnitude of metal's elastic deformation energy. Therefore, hardness is a comprehensive performance indicator that characterizes a combination of different physical quantities such as elasticity, plasticity, strain hardening, strength, toughness, and more. In production, indentation methods, especially the Brinell hardness test, are widely applied.

1.Brinell Hardness (HBW):

Originating in 1900, proposed by the Swede J.B. Brinell, it has a long history and wide application. In this method, a tungsten carbide ball is pressed into the material's surface under a certain load, and the size of the resulting indentation is used to calculate the hardness. Characteristics include large indentation size (several millimeters) and stable data. It is suitable for alloys with medium to low hardness, such as gray cast iron and bearing alloys.

Brinell Hardness Tester

Brinell Hardness Tester Testing Principle

2.Rockwell Hardness (HRA/HRB/HRC):

Proposed by the American Rockwell in 1919, this method uses a diamond cone or a hard alloy ball as the indenter. Under external force, the diamond indenter is pressed into the material's surface, and the resulting indentation depth is used to calculate the hardness. Characteristics include small indentation size (less than 1mm), minimal damage to the workpiece surface, rapid operation, and immediate data reading. It is commonly used for finished product inspection in steel manufacturing.

Rockwell Hardness Tester

Rockwell Hardness Tester Testing Principle

3.Vickers Hardness (HV):

Originating in 1925, proposed by R.L. Smith and G.E. Sandland in the UK, the Vickers hardness method uses a diamond pyramid indenter. Similar to the Brinell method, the indentation size is used to calculate hardness, but with a different geometric shape of the indenter. Characteristics include a testing principle similar to Brinell hardness, suitability for testing both soft and hard materials, and more applications in research institutions.

Vickers Hardness Tester

Vickers Hardness Tester Testing Principle

4.Hardness Overview for Various Products:

The main purpose of hardness testing is to determine the suitability of a material for a given application or the specific treatment it has undergone. Hardness testing is relatively easy to conduct, making it the most common inspection method for metals and alloys.

Item	Product photo	Hardness
Ring die		HRC 52 - 55
Roller shell		HRC 58 - 62
Hammer beater		Hole area < HRC 28, Corners area: HRC 58 - 62 Tungsten carbide: HV 2375
Sieve		HV 150 - 180
Gear ring		HRA 90 - 92
Hammer head		HRC 92.2
Flat die		HRC 49 - 52