Intergranular Oxidation IGO Testing Services
Accredited intergranular oxidation IGO testing from Infinita Lab, performed to the exact standard requirements - accurate, reproducible results with full documentation for compliance, R&D, and quality control programs.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
What Is Intergranular Oxidation IGO?
Intergranular oxidation (IGO) testing is a metallographic evaluation that measures how far oxides have penetrated along a steel part’s grain boundaries at the surface. In gas-carburized and carbonitrided steels, the furnace atmosphere contains trace oxygen that reacts with alloying elements such as silicon, manganese, and chromium, which have a greater affinity for oxygen than iron does. The resulting oxides precipitate along austenite grain boundaries just beneath the surface, and the depleted matrix next to them can transform to softer, non-martensitic products on quenching. This condition can reduce bending fatigue performance in loaded parts such as gears and shafts, so many customers and industry specifications limit it. The method starts with a representative section cut perpendicular to the surface. That section gets mounted in an edge-retentive medium, then ground and polished to a scratch-free finish. It’s examined unetched, since etching can obscure the fine oxide network. Under an optical microscope, usually at several hundred times magnification, the analyst identifies the dark oxide stringers and measures how deep they reach from the surface. Depth is commonly reported as a maximum value or as an average of the deepest readings across several fields, depending on the governing requirement. Intergranular oxidation evaluation is a metallographic technique defined by customer or industry specifications rather than a single published ASTM test method. So the acceptance criteria, number of fields, and reporting basis must be agreed before testing begins. Sample preparation follows general metallographic practice such as ASTM E3, while the measurement rules come from the drawing, the heat-treat specification, or the purchaser’s quality requirements. Infinita Lab coordinates this evaluation through qualified metallography partners and delivers documented micrographs with measured penetration depths.
Applications and Benefits of Intergranular Oxidation IGO Testing
Scope
IGO testing evaluates:
- The evaluation examines grain-boundary oxide penetration at the surface of steel parts, most often those that were gas carburized or carbonitrided.
- It’s a metallographic technique defined by customer or industry specifications rather than a single published ASTM test method.
- Cross sections are cut perpendicular to the surface, which puts the full depth of the oxide network in view.
- Polished, unetched specimens keep oxide stringers distinct from the surrounding matrix.
- Measurement runs from the part surface to the deepest point where continuous grain-boundary oxide can be identified.
- Reporting follows the governing requirement: a maximum depth, an average of the deepest readings in several fields, or both.
- Associated surface features, such as globular oxides and softer transformation products visible in the near-surface layer, can be documented too.
- Production parts are covered, as are process-qualification coupons and failure-analysis specimens.
- Acceptance limits come from the drawing, heat-treat specification, or purchaser, not from the method itself.
Applications
- Verifying that a gas carburizing or carbonitriding process holds surface oxidation within customer limits.
- New furnaces, atmosphere control settings, or heat-treat suppliers for drivetrain components can be qualified.
- Gears, pinions, shafts, and bearing components, where bending fatigue life is critical.
- Comparing conventional atmosphere processing with vacuum or low-oxygen carburizing.
- Root-cause analysis of premature fatigue cracking that starts at the surface.
- Checking alloy grades with higher silicon, manganese, or chromium content that are more prone to oxide formation.
- High-temperature oxidation damage in alloys where oxide advances along grain boundaries can be reviewed too.
Benefits
- Reveals subsurface oxide networks that are invisible to visual inspection and to hardness testing alone.
- Quantitative depth data can be tracked from lot to lot and trended over time.
- It helps catch atmosphere-control drift before a large production volume is affected.
- Supplier qualification gets documented, comparable evidence.
- Micrographs make findings easy to review with design and quality teams.
- The risk of fatigue-related field failures linked to surface condition goes down.
Our Testing Procedure
Sample Preparation
Specimens are sectioned and polished according to ASTM E3 to expose grain boundaries.
1Thermal/Exposure Simulation
Samples may be evaluated after heat treatment (typically 800–950°C exposure conditions).
2Microstructural Examination
Optical microscopy or SEM is used to identify oxide penetration along grain boundaries.
3Data Analysis
Oxidation depth (µm) and severity are measured and compared with acceptance criteria.
4Test parameters and requirements
| Parameter | Details |
|---|---|
| Standard | ASTM E3, ASTM E407 (metallography) |
| Applicable Materials | Steels, superalloys, titanium alloys |
| Temperature Exposure | ~800–950°C (process dependent) |
| Oxidation Depth | ~5–25 µm typical |
| Measured Outputs | Oxide depth, microstructure, affected zone |
| Detection Method | Optical microscopy / SEM |
| Accuracy | µm-level measurement precision |
- Precision Cut-Off Saw – produces low-damage cross sections without altering the surface layer.
- Hot Compression Mounting Press – holds sections in hard resin, which preserves edge flatness.
- Automated Grinder-Polisher – repeatable, scratch-free polished surfaces come from its diamond stages.
- Inverted Metallurgical Microscope – for unetched examination of the polished surface at high magnification.
- Digital Imaging and Measurement Software – captures micrographs and calibrated depth measurements.
- Scanning Electron Microscope with EDS – used when composition confirmation is required, to identify oxide chemistry.
Equipment and Instrumentation Used for Testing
What You Receive: Test Report, Data, and Certification
- Measured maximum depth of intergranular oxide, in micrometers, for each examined location.
- Average depth of the deepest readings across the specified number of fields, when required.
- Calibrated micrographs showing the oxide network and the measurement locations.
- Notes on related surface features such as globular oxides or non-martensitic near-surface structure.
- A pass or fail statement against the stated specification, when acceptance limits are provided.
- Finally, a complete report with specimen identification, method description, and traceable records.
Intergranular Oxidation IGO FAQs
IGO is a form of localized oxidation where oxygen diffuses along grain boundaries and reacts with alloying elements, forming oxides that weaken the material and reduce mechanical performance in high-temperature environments.
IGO is caused by exposure to oxygen-containing atmospheres during high-temperature processes such as carburizing or heat treatment. Oxygen reacts with elements like chromium and manganese along grain boundaries.
IGO occurs at high temperatures due to oxidation, while intergranular corrosion typically occurs in aqueous environments due to chemical attack. Both affect grain boundaries but have different mechanisms and conditions.
IGO is measured using metallographic techniques, where polished samples are examined under microscopes to determine oxide penetration depth and severity along grain boundaries.
IGO testing helps detect hidden material degradation that can reduce fatigue life and cause premature failure, especially in critical components used in aerospace, automotive, and power generation industries.
The term “IGO test” can refer to different tests depending on the industry or application. Please share what IGO stands for or the material being tested so I can provide the correct procedure.
ASTM E381 evaluates the internal structure of steel bars, billets, blooms, and forgings through macroetch testing. A prepared specimen is etched with a suitable chemical reagent, revealing segregation, cracks, porosity, and other structural defects for visual examination.
Why Choose Infinita Lab for Intergranular Oxidation IGO Testing
When your Intergranular Oxidation IGO results have to hold up - for compliance, a customer audit, or an engineering decision - accuracy and an unbiased third-party report matter more than price. Infinita Lab routes your intergranular oxidation IGO testing to ISO/IEC 17025-accredited U.S. partner labs with hands-on method experience, so you get defensible data, transparent reporting, and turnaround times built around your project deadline - not ours.
Looking for an Accredited Partner for Intergranular Oxidation IGO Testing?
Send query us at hello@infinitalab.com or call us at (888) 878-3090 to learn more about our services and how we can support you.
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