As a supplier of Webster Hardness Testers, I've often been asked about the various factors that can influence their performance. One such factor that might not be on everyone's radar but holds significant importance is humidity. In this blog, I'll explore the effects of humidity on the performance of a Webster Hardness Tester.
Basic Understanding of Webster Hardness Testers
Before delving into the impact of humidity, let's first understand what a Webster Hardness Tester is. Webster Hardness Testers are widely used for rapid and non - destructive hardness testing of non - ferrous metals, such as aluminum, copper alloys, and certain plastics. They are portable, easy to use, and provide a quick indication of the material's hardness. We offer a range of Webster Hardness Testers, including the Digital Webster Hardness Tester and the W - 20 Webster Hardness Tester, which are popular among our customers for their accuracy and reliability.
How Humidity Can Affect the Tester's Components
Mechanical Components
Webster Hardness Testers have several mechanical parts, such as the indenter, spring, and plunger. High humidity can lead to the corrosion of these metal components. When exposed to a humid environment for an extended period, the metal starts to oxidize. Rust can form on the indenter, which is the part that actually penetrates the material during testing. This rust can change the shape of the indenter tip. As a result, the penetration depth of the indenter into the test material may be different from what it should be under normal conditions. A corroded indenter might not be able to penetrate the material smoothly, leading to inaccurate hardness readings.
The spring in the hardness tester is also sensitive to humidity. Excessive moisture can cause the spring to lose its elasticity over time. If the spring becomes less elastic, it may not provide the correct amount of force required for the indenter to penetrate the material. This can lead to either over - or under - estimation of the material's hardness. For example, a weakened spring may not push the indenter deep enough, resulting in a higher than actual hardness reading.
Electronic Components (in Digital Testers)
For digital Webster Hardness Testers, humidity can pose an even greater threat to the electronic components. Moisture can seep into the circuit boards and cause short - circuits. The sensors in digital testers, which are responsible for measuring the penetration depth and converting it into a hardness value, are very sensitive. If moisture gets into these sensors, it can disrupt their normal functioning. This may lead to erratic readings or even complete failure of the tester.
High humidity can also cause a build - up of electrostatic charges on the electronic components. These electrostatic charges can interfere with the electrical signals transmitted within the tester, leading to inaccurate hardness measurements.
The Impact on Test Materials
Moisture Absorption by the Test Material
Humidity can also affect the test material itself. Non - ferrous metals, which are commonly tested using Webster Hardness Testers, can absorb moisture from the air. When the material absorbs moisture, its internal structure may change slightly. For example, in the case of aluminum alloys, moisture absorption can lead to the formation of hydrates within the material. These hydrates can alter the material's hardness. When testing a material that has absorbed moisture, the hardness reading may not represent the true hardness of the dry material.
Surface Condition
The surface of the test material can be affected by humidity. In a humid environment, a thin layer of moisture can form on the surface of the material. This moisture layer can act as a lubricant between the indenter and the material during testing. As a result, the indenter may slide more easily over the surface, leading to an incorrect measurement of the material's resistance to penetration. This can cause the hardness reading to be lower than the actual hardness of the material.
Testing in Different Humidity Conditions
In our laboratory, we conducted a series of tests to observe the impact of humidity on the performance of our Webster Hardness Testers. We used a Digital Webster Hardness Tester to test samples of aluminum alloy under different humidity levels.
We set up three different humidity chambers with relative humidity levels of 20%, 50%, and 80%. We measured the hardness of the aluminum alloy samples multiple times in each chamber. The results were quite revealing. At 20% relative humidity, the hardness readings were relatively stable, and the deviation between multiple measurements was within an acceptable range.
However, when the humidity increased to 50%, we noticed a slight increase in the variability of the hardness readings. Some of the readings were slightly lower than what we obtained at 20% humidity. As the humidity reached 80%, the situation became more pronounced. The readings were much more scattered, and in some cases, the difference between consecutive measurements was significant. This indicated that high humidity had a negative impact on the accuracy and repeatability of the hardness testing.
Mitigating the Effects of Humidity
Storage and Handling
To minimize the effects of humidity on Webster Hardness Testers, proper storage and handling are crucial. When not in use, the testers should be stored in a dry environment, preferably in a cabinet with a desiccant. A desiccant can absorb the moisture in the air, keeping the storage environment dry.
Before using the tester, it should be allowed to reach the ambient temperature to prevent condensation from forming on its components. If the tester has been stored in a very dry environment and is then taken to a humid environment, it's important to let it acclimate gradually to avoid sudden changes in humidity that could damage the components.
Regular Maintenance
Regular maintenance of the Webster Hardness Tester is essential. The mechanical components should be inspected for signs of corrosion regularly. If any rust is detected, it should be removed carefully using appropriate cleaning agents and tools. The spring should be checked for its elasticity, and if necessary, replaced.
For digital testers, the circuit boards should be inspected for any signs of moisture damage. It's also a good practice to clean the sensors regularly to ensure their proper functioning.
Conclusion
Humidity can have a significant impact on the performance of Webster Hardness Testers. It can affect both the tester's components and the test material, leading to inaccurate hardness readings. As a supplier, we understand the importance of providing our customers with accurate and reliable testing equipment. That's why we recommend taking the necessary precautions to minimize the effects of humidity.
If you're in the market for a Webster Hardness Tester or need more information about how to use and maintain them in different environmental conditions, we're here to help. Our team of experts can provide you with detailed guidance and support. Contact us to start a discussion about your specific requirements and let's find the best solution for your hardness testing needs.
References
- ASTM E140 - 12, "Standard Hardness Conversion Tables for Metals Relationship Among Brinell Hardness, Vickers Hardness, Rockwell Hardness, Superficial Hardness, Knoop Hardness, and Scleroscope Hardness".
- ISO 6506 - 1:2014, "Metallic materials — Brinell hardness test — Part 1: Test method".