Core Hardness Testing by Micro Vickers Hardness Tester

In metal surface strengthening processes such as carburizing, nitriding and induction quenching, the testing of core hardness and hardened layer depth, as well as defects in heat treatment processes, will affect the overall mechanical properties of products. We use a micro Vickers hardness tester to complete the entire testing process and control the hardened layer depth, a key quality control indicator.

1.Sample Preparation

· Select the test part or standard sample and cut the cross section to ensure the tested surface is flat, deformation-free and burr-free.

· Grind and polish the cross section to remove the surface oxide layer and machining marks.

· Etch as required by relevant standards (if necessary) to clearly distinguish the surface layer from the core structure.

2.Testing of Core Hardness

We use Model MHV-1000AT micro Vickers hardness tester to complete the entire test process.

· Securely place the sample on the stage of the Micro Vickers hardness tester and align it to the core area (away from the surface hardened layer).

· Set the test force (commonly HV1.0) and dwell time, and confirm that the equipment is properly calibrated.

· Select 3 to 5 uniform measuring points on the core, avoiding defects such as porosity, air holes and inclusions.

· Start the measurement; the hardness values are read automatically, and the average value is taken as the final core hardness result.

3.Hardened Layer Depth Testing

· Arrange test points at equal intervals along a straight line from the surface to the core, and set the step distance in accordance with relevant standards (commonly 10–50 μm).

· Measure the hardness point by point, and record the hardness value and corresponding depth of each position.

· Continue the measurement until the hardness stabilizes below the critical value, then stop the test.

4.Judgment of Effective Hardened Layer Depth (CHD)

· Determine the critical hardness value in accordance with corresponding standards (e.g., GB/T 9450).

· Locate the position where the hardness first drops to the critical value; this depth is defined as the effective hardened layer depth.

5.Data Processing and Reporting

· Plot the hardness distribution curve with depth as the horizontal axis and hardness as the vertical axis to present the hardness gradient.

· Organize data including core hardness, hardened layer depth and hardness curve to generate the test report.

Above hardness and depth testing are carried out by

Q-80Z metallographic cutting machine

MP-2000 automatic metallogtaphic grinding and polishing machine

MHV-1000AT micro Vickers hardness tester

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