ASTM E92 Standard Test Methods for Vickers Hardness and Knoop Hardness of Metallic Materials

Get Certified ASTM E92 Testing for Reliable Hardness Measurement

This method verifies that Vickers and Knoop hardness of metallic materials is measured using standard indentation procedures. Laboratory testing is essential for experienced laboratories performing material properties analysis, heat treatment verification, and quality control. ASTM E92-certified testing is used for quality control, material verification, and research and development for metals, alloys, and other materials. The tests are conducted in a professional laboratory that guarantees that they comply with the standard requirements and gives confidence in the results. In critical applications, engineers and quality control professionals depend on certified testing to verify hardness values, guaranteeing material performance. 

• Materials: Metallic materials such as ferrous and nonferrous metals and alloys.
• Purpose: Evaluation, quality control, research, and development of materials.
• Property measured: Vickers hardness (HV) and Knoop hardness (HK) based on indentation measurements.
• Method: A controlled test force is applied to a diamond indenter, a measurement of the resulting indentation is taken, and hardness values are calculated.
• Result: Vickers/Knoop Hardness No and Test force/Indentation measurements.
• Test limitations: Vickers hardness is covered for test forces from 1 gf to 120 kgf; Knoop hardness for test forces from 1 gf to 2 kgf.
• Use conditions: Testing is performed at ambient laboratory temperature under controlled conditions. Hardness values reflect material behavior at the test temperature and may differ under service conditions at elevated or cryogenic temperatures.
• Applications: It includes metal manufacturing, quality control, heat treatment verification, weld testing, research and development, and failure analysis. 

What are the Uses of ASTM E92?

ASTM E92 testing is used to assess the hardness of metallic materials, which is beneficial for manufacturers and researchers. These test results are used for quality control, material verification, and research and development. This standard is used widely in the metals manufacturing, automotive, aerospace, and research sectors. This standard-

• Relates the hardness of many metals to tensile strength.
• Represents the ability of materials to resist damage and be bent or stretched.
• Carries out testing of thin or small specimens.
• Facilitates the assessment of certain phases or constituents.
• Detects differences in softness and hardness of material.
• Participates in quality control of manufacturing processes.
• Helps in the research and development process. 

Which materials can be tested under ASTM E92?

ASTM E92 applies to metallic materials, such as ferrous and nonferrous metals and alloys. Other materials may also be tested using these procedures, but require special considerations. Common materials are steel, aluminum, copper, titanium, and their alloys. The method is applicable for samples that are too thin to take macroindentation hardness tests or too small. 

Why is ASTM E92 Important? 

ASTM E92 specifies the Vickers and Knoop hardness of metallic materials. The test method provides requirements for hardness testing machines and procedures to assist manufacturers in assessing material properties and quality control. The standard provides uniformity in test methods and data interpretation among laboratories. The Vickers and Knoop hardness tests are vital for materials evaluation, quality control in manufacturing processes, and Research and Development. Engineers use this standard to confirm heat treatment, measure a weld’s quality, and assess performance in critical applications. 

ASTM E92 Testing Process and Data Collection

Preparation of the specimen surface for testing starts with grinding and polishing to a mirror finish. The technician mounts the specimen securely and chooses the indenter for the test. The test blocks are used to ensure machine calibration. They deliver the chosen test force within 10 seconds with no vibration or shock, and hold the force for the specified dwell time. They use a measuring microscope with a calibrated diagonal head to measure indentation diagonals. The test force is used together with the measured dimensions of the indentations to calculate Vickers hardness (HV) or Knoop hardness (HK). Laboratories take samples for QA/QC, material verification, and research and development. 

Common Challenges and Troubleshooting

Typical problems associated with ASTM E92 testing are surface preparation of specimens, vibrations during testing, and measurement errors during indentation. These issues affect the accuracy of hardness determination. Inaccurate surface preparation results in inaccurate indentation measurements. The indentation shape is distorted due to vibrations during force application. The error in measurement may be due to insufficient calibration of the microscope or the skills of the operator. Technicians need to make sure all specimens are properly polished, all measuring systems are calibrated regularly, and tables are vibration-isolated. The use of standard procedures and equipment maintenance guarantees reliable results, especially with the assistance of experienced technicians.

• Engineers apply these results to ensure compliance of the materials and product performance. 
• The laboratory provides Vickers hardness (HV) or Knoop hardness (HK) numbers.
• Laboratory technicians record the test force applied during the measurement.
• Analysts record the diagonal indentation for Vickers testing or the long diagonal for Knoop testing.
• Laboratories obtain accurate results through standardized specimen preparation, calibration, and testing conditions. The results show the material hardness, wear resistance, and ductility.

Link to ASTM E92