The Inspection Methods For Nickel-based Alloys

The inspection methods for nickel-based alloys (such as Inconel, Hastelloy, etc.) need to be optimized based on their specific material characteristics (such as high temperature resistance, corrosion resistance, non-magnetism, etc.). The following are the commonly used non-destructive testing (NDT) methods for nickel-based alloys and their technical points:

 

1. Ultrasonic Testing (UT)

Applicable scenarios: Detection of internal defects (such as cracks, pores, inclusions, etc.);

Applicable to thick-walled tubes, rods, forgings, etc.

Technical points: Probe selection: Longitudinal wave straight probe (for internal defect detection)

Transverse wave oblique probe (for detecting transverse cracks, recommended 45° - 70°)

Coupling agent: High-temperature glycerol or special coupling agent (suitable for the high density characteristic of nickel-based alloys)

Calibration block: A block matching the acoustic properties of nickel-based alloys (such as ASTM E317) is required

Phase array ultrasonic (PAUT): Can improve detection efficiency and accuracy, applicable to workpieces with complex shapes

Advantages: Can detect deep defects

Not affected by material magnetism

 

2. Penetrant Testing (PT)

Applicable scenarios: Detection of surface-opening defects (such as cracks, pinholes, etc.)

Applicable to the surface of all nickel-based alloys

Technical points: Penetrant type: Fluorescent penetrant (high sensitivity)

Sensitized penetrant (suitable for on-site detection)

Cleaning agent: Must be low chlorine (to prevent chlorine-induced stress corrosion)

Imaging agent: Dry powder or wet-type imaging agent

Advantages: Simple operation, low cost

Can detect workpieces with complex shapes

 

3. Eddy Current Testing (ET)

Applicable scenarios: Detection of surface and near-surface defects (such as cracks, folds, pores, etc.)

Applicable to thin-walled tubes, wire rods, plates

Technical points: Frequency selection: Thin wall (<1mm): 100 - 500 kHz

Medium wall thickness (1 - 3mm): 50 - 100 kHz

Thick wall (>3mm): 10 - 50 kHz

Differential probe: Enhances the detection sensitivity of tiny defects (can detect cracks as deep as 0.1mm)

Calibration standard: Requires the use of nickel-based alloy standard defect specimens

Advantages: Fast detection speed, suitable for automated online detection

No coupling agent required, non-contact detection

 

4. Nickel-based alloy flaw detection standards

Standard	Scope of Application
ASTM E213	Ultrasonic testing standard
ASTM E309	Eddy current testing standard
ASTM E94/E1032	Radiographic testing standard
ASTM E165	Penetrant testing standard
ASTM E709	Magnetic particle testing standard
ASME BPVC	Testing requirements for nickel-based alloys used in nuclear power plants

PS: Ultrasonic testing equipment