1. What is coating hardness?

Hardness is the crucial parameter in understanding the structural stability of a material you use, whether it in the form of a coating or a solid mass. Specifically, hardness is the relative measure of superficial physical strength of solid material when external mechanical force is applied. Every solid material has a measurable hardness that tolerates a particular amount of external damaging force exerted during cutting, rubbing, grinding, rolling, etc.

2. Why does coating hardness matter?

Component durability is a key influencing factor in every manufacturing business. Elevating the damage tolerance level of components improves the item’s durability and service longevity. The hardness value indirectly indicates the damage tolerance of material. This value also helps to understand the durability of respective material components in real-world applications.

3. Who evaluates coating hardness?

Hardness evaluation is a key measurement in many industries for these purposes:

  • Process & product development. During process development, the hardness evaluation helps in the design and development of component material.
  • In manufacturing, the hardness values guide engineers in making components.
  • Quality control. Quality departments evaluate hardness value to maintain the quality of components and ensure consistency.

4. How is coating hardness measured?

The hardness of a material can be evaluated in many ways depending upon the targeted application. In industries, well-defined ISO®/ASTM®, ASME® standards are followed to conduct specific hardness testing. Hardness values are measured from the top surface of a material to several nanometer-to-microns-to-millimeters down below the surface of the material at various loading/unloading conditions.

Fig. 1 below shows typical method of measuring the hardness of material surface according to ISO 14577/ASTM E 2546. Here, the material tip A at certain load L1 and speed S1 penetrates the material B. The hardness of material B is the relative measure of its ability to withstand the damage induced by tip A. In the diagram the dotted arcs represent possible damage area within material B.

5. How do you adjust for different applications and materials?

In general, loading and unloading values depend upon the application and materials of interest. At lower loads, the more superficial hardness of the material can be evaluated. In such conditions, more accurate control of factors such as temperature, contamination, vibration, humidity, and other factors must be maintained during the test. Depending upon the testing methods, units of hardness values are measured in Mohs Scale, Vickers Pyramid Numbers (HV) or in Pascals. Table 1 shows the hardness value of carbon in graphite and diamond form.

Carbon FormMohs ScaleVickers
Graphite (Soft)1-27-11
Diamond (Very Hard)1010000

Figure 1. ISO14577/ASTM E2546 method of hardness evaluation. Table 1. Shows the hardness of carbon in its graphitic and diamond form.

At Vapor Technologies, Inc. (VaporTech®), our R&D lab conducts extensive testing for each custom coating recipe we develop. In addition to hardness, we test and optimize for composition and structure, appearance (including color, gloss, and texture), mechanical properties (for functional/tribological/biocompatible coatings), and corrosion. Our coating development and optimization services create the recipes your VaporTech® coating system uses to create specific coatings. Once we load the recipes, the operator only has to press a button to change a recipe for a different coating.

 

ISO® is a registered trademark of the International Organization for Standardization.

ASTM® is a registered trademark of the American Society for Testing Materials.

ASME® is a registered trademark of the American Society of Mechanical Engineers.

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