I. Rockwell Hardness (HR)
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1. Principle

Using a diamond cone (with a 120° apex angle) or a steel ball (with a diameter of 1.59mm or 3.18mm) as the indenter, press it into the material surface under the action of an initial load and a main load. The hardness value is calculated based on the indentation depth—the deeper the indentation, the lower the hardness value.

2. Characteristics

- Fast testing speed and simple operation, suitable for batch testing.
- Capable of testing medium to high hardness materials.
- Multiple scales are available based on material hardness:
- HRA: Uses a 60kg load and a diamond indenter, suitable for extremely hard materials such as cemented carbides.
- HRB: Uses a 100kg load and a steel ball indenter, suitable for soft steel, copper alloys, aluminum alloys, etc.
- HRC: Uses a 150kg load and a diamond indenter, suitable for quenched steel, high-hardness alloys, etc.

3. Typical Applications

Widely used for rapid hardness testing of metal products such as cutting tools, bearings, gears, and cast iron parts.

II. Brinell Hardness (HBW)

1. Principle

A hard alloy ball of a certain diameter (usually 10mm) is pressed into the material surface under a specified load, and the hardness value is calculated based on the indentation diameter.
Common types of Brinell Hardness:

- HBS: Uses a steel ball indenter, suitable for materials with hardness ≤ 450 HB, such as soft steel, gray cast iron, and non-ferrous metals.
- HBW: Uses a hard alloy ball indenter, suitable for materials with hardness ≤ 650 HB, and is the mainstream form of modern standards.

2. Characteristics

- Stable results and good repeatability.
- Suitable for soft to medium hardness metals.
- The indentation is relatively large, so it is not suitable for thin-walled or small-sized parts.

3. Typical Applications

Hardness testing of raw materials and rough-processed parts, such as annealed steel, cast iron, and non-ferrous metals and their alloys.

III. Vickers Hardness (HV)

1. Principle

A square pyramid diamond indenter with a 136° apex angle is used to press into the material surface under a specified load, and the hardness value is calculated based on the diagonal length of the indentation.

2. Characteristics

- High precision: Enables accurate hardness measurement, even for extremely small areas (e.g., micro-regions of materials).
- Wide application range: Suitable for testing materials across a broad hardness spectrum, from soft metals (like aluminum alloys) to ultra-hard materials (such as cemented carbides).
- Minimal indentation: The tiny indentation left on the material surface avoids damaging workpieces, making it ideal for thin-walled parts, surface coatings, and micro-area hardness testing.

3. Typical Applications

It is widely used for hardness testing of precision components, surface coatings, and thin sheets—for example, hardness measurement of mobile phone shell coatings to verify wear resistance. Additionally, it is indispensable in scientific research for hardness analysis of microscopic regions, such as hardness testing of grain boundaries and phase boundaries in materials to study material microscopic properties.

4.Comparison of the Three Hardness Testing Methods

5.Summary
The three hardness testing methods each have their own advantages. The most appropriate method should be comprehensively selected based on material characteristics, sample shape, hardness range and precision requirements to obtain the most reasonable test results.

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