Application framework for selection and method discussions; not a customer test report.
Purpose
Welds, heat-affected regions and additively manufactured parts.
Preparation route
Section across the relevant weld or build direction and retain orientation records. Define preparation needs separately for macro examination, microscopy and hardness testing.
Checkpoints
When examining pores, cracks or lack of fusion, exclude pull-out and grinding artifacts. Use the applicable evaluation criteria.
Equipment stages
Cutting → Mounting → Grinding and polishing → appropriate microscopy and testing.
Record sampling position, consumables, actual settings and images. Evaluate using the agreed method.
Typical inspection scenarios
Fusion-welded butt joint of low-alloy high-strength steel (Q345 grade)
- Challenge
- The weld metal, HAZ and base metal differ greatly in structure and hardness, so macroscopic morphology and clear microstructures of each zone must be obtained on the same section; defects such as lack of fusion and pores are fine and distributed between passes, and a wrongly oriented section easily misses them.
- Preparation & method
- Take a transverse section perpendicular to the weld axis on a wet abrasive cut-off machine, avoiding the arc start/stop ends. Rough grind to P320 and macro-etch (4% nital, or a ferric chloride hydrochloric aqueous reagent where needed) to confirm weld profile, fusion lines and defect locations; then continue grinding from P400 to P2000, polish with 3 μm then 1 μm diamond, etch with 4% nital, and examine the columnar weld grains, coarse-grained HAZ and base metal zone by zone.
- Reference standards
- GB/T 26955 Destructive tests on welds in metallic materials — Macroscopic and microscopic examination of welds; ISO 17639 Destructive tests on welds in metallic materials — Macroscopic and microscopic examination of welds; GB/T 13298 Metallographic examination methods for metals
Selective laser melted (SLM) additively manufactured 316L stainless steel component
- Challenge
- Melt-pool boundaries (fish-scale tracks) and columnar grains grow epitaxially along the build direction, giving strongly anisotropic structures that differ greatly between transverse and longitudinal sections, so both orientations must be compared; fine pores and lack-of-fusion defects are small and randomly distributed and easily missed; high as-built residual stress means careless sectioning can introduce artifact cracks.
- Preparation & method
- Section both parallel (XZ) and perpendicular (XY) to the build direction on a low-speed precision saw at low feed with ample coolant; cold mount. Grind with SiC papers from P400 to P2000, polish with 3 μm then 1 μm diamond and finish with 0.05 μm colloidal silica. Etch with aqua regia (or electrolytically in 10% oxalic acid at 6 V for a few seconds) to reveal melt-pool boundaries and columnar grains; examine at 100×–500× under bright field for melt-pool morphology, cross-layer epitaxial growth and texture, using dark field/polarized light to assist inspection of micro-pores and lack of fusion; measure micro-Vickers hardness (HV0.5) on both orientations to assess anisotropy; quantify porosity by image analysis.
- Reference standards
- ASTM F3184 Standard Specification for Additive Manufacturing Stainless Steel Alloy (UNS S31603) with Powder Bed Fusion; GB/T 13298 Metallographic examination methods for metals; ASTM E112 Standard Test Methods for Determining Average Grain Size
Scenarios are method examples, not customer test reports; confirm the process per specimen.
MICROCRE learning notes · confirm the method for the specimen.