Overview
ISO 19477:2016 specifies a laboratory method to measure the in‑plane Young’s modulus (room temperature) of thermal barrier coatings (TBCs) applied by thermal spraying. The method uses a four‑point beam‑bending test on three specimen types - bare substrate, substrate with bond coat (BC), and substrate with full TBC (bond coat + ceramic top coat, TC) - and applies composite‑beam theory to extract the Young’s modulus of each layer from measured force–strain slopes.
Keywords: ISO 19477:2016, Young’s modulus, thermal barrier coatings, beam bending, TBC, four‑point bending, thermal spraying.
Key technical topics and requirements
- Principle: Measure force–strain diagrams for three specimen configurations and compute moduli using composite‑beam formulas.
- Apparatus: Four‑point bending jig, a testing machine compliant with ISO 7500‑1, and strain measuring equipment (strain gauge on coating surface).
- Specimen types & preparation:
- Substrate, BC specimen (substrate + bond coat), and TBC specimen (substrate + BC + TC).
- Substrate thickness typically 1.5–3.0 mm; BC minimum thickness 0.10 mm; TC minimum thickness 0.20 mm.
- Side surfaces of coated specimens must be polished to remove edge‑deposited coating without damaging the layers.
- Thickness tolerance for substrates: ±0.01 mm.
- Four‑point jig geometry and rollers:
- Distance between load rollers: 15–30 mm; support rollers spaced 3× the load‑roller distance.
- Roller radii: 2.0–3.0 mm; surface roughness ≤ 0.4 μm Ra.
- Measurement specifics:
- Strain gauge length normally ≤ 5 mm; strain accuracy ±1%.
- Test speed ≤ 0.5 mm/min; force range chosen to avoid coating damage or plastic substrate deformation.
- Repeatability: each force–strain measurement repeated (three runs per specimen; three specimens per condition).
- Special cases: Annex A provides procedures for specimens with significant porosity (to avoid adhesive penetration when attaching gauges).
- Calculations: Use slopes ΔP/Δε from force–strain diagrams and composite‑beam relations to compute Young’s moduli of substrate, BC and TC.
Practical applications and who uses this standard
- Users: Materials laboratories, coating manufacturers, quality assurance teams, aerospace and gas‑turbine component engineers, and researchers studying thermally sprayed TBC systems.
- Applications: Characterizing mechanical stiffness of TBC layers for design validation, life‑prediction models, residual stress analysis, failure investigation, process development and acceptance testing of thermally sprayed coatings used on hot‑section components (e.g., blades, vanes, combustors).
Related standards (normative references)
ISO 19477:2016 provides a reproducible, standardised route to quantify the Young’s modulus of multilayer thermal barrier coatings produced by thermal spraying, enabling consistent material characterization and engineering decision‑making.
Open preview (PDF)Metallic and other inorganic coatings — Measurement of Young's modulus of thermal barrier coatings by beam bending