Testing the internal and external surface quality of molybdenum crucibles requires comprehensive evaluation from multiple dimensions such as surface defects, dimensional accuracy, surface roughness and composition analysis. The following are specific testing methods and key points:
- Surface defect detection
- Visual inspection
Tools: high power magnifying glass (10-50×) or industrial endoscope.
Inspection contents: cracks, pores, inclusions, scratches, oxide layers.
Application scenario: Preliminary screening of surface defects, suitable for the outer surface of large-sized crucibles.
- Fluorescent Penetrant Testing (PT)
Principle: The fluorescent liquid penetrates into the surface opening defect and the image is displayed under the irradiation of ultraviolet light.
Advantages: Can detect micron-level cracks, sensitivity ≤ 0.5μm.
Scope of application: inner wall of crucible and complex structures.
- Ultrasonic Testing (UT)
Principle: High-frequency ultrasonic reflection detection of internal and near-surface defects.
Parameters: frequency 5-10MHz, coupling agent is glycerol or water.
Advantages: Can detect internal defects up to 10mm in depth.
- Dimensional accuracy detection
- Coordinate Measuring Machine (CMM)
Accuracy: ±(0.3+L /300)μm (L is the measuring length, unit: mm).
Inspection contents: inner and outer diameters, height, wall thickness, roundness, and straightness.
Application scenario: Final inspection after high-precision processing.
- Laser Scanner
Principle: Laser triangulation method generates 3D point cloud model.
Advantages: High detection efficiency, suitable for complex surfaces.
Output: Geometric tolerance report (such as flatness ≤ 0.02mm).
- Surface roughness detection
- Stylus roughness tester
Parameters: Ra, Rz, Rmax and other parameters.
Standard: The crucible used in sapphire single crystal growth furnace requires Ra≤0.4μm.
Testing points: Take at least 5 points and take the average value.
- Optical interferometer
Principle: White light interference generates surface microscopic morphology.
Advantages: Non-contact detection, avoids scratching the surface.
Application: Inner wall inspection of high purity molybdenum crucible.
- Composition and performance testing
- Oxygen content analysis
Method: Inert gas fusion infrared absorption method.
Standard: Oxygen content ≤ 0.005wt % (high-end applications).
Equipment: LECO ONH836 oxygen, nitrogen and hydrogen analyzer.
- Hardness test
Method: Vickers hardness (HV) or Rockwell hardness (HR).
Standard: HV200 -300 (pure molybdenum), HV≥1000 (molybdenum alloy).
Equipment: 402MVD Micro Vickers Hardness Tester.
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