Overview
ISO 14188:2012 - Metallic and other inorganic coatings - specifies laboratory test methods for measuring thermal cycle resistance and thermal shock resistance of thermal barrier coatings (TBCs). The standard defines steady cyclical heating/cooling procedures to evaluate resistance to thermal strain (spalling) and a heating‑and‑quenching technique to measure loss of tensile adhesive strength after thermal shock. ISO 14188:2012 is intended for screening TBC systems (materials and processing) and is not for control of thermal spraying processes.
Key topics and technical requirements
- Test methods
- Thermal cycle resistance: alternate exposure to high‑ and low‑temperature baths (steady cyclical heating/cooling) and measurement of spalling area versus number of cycles.
- Thermal shock resistance: furnace heating followed by water quench; measurement of tensile adhesive strength degradation.
- Acceptance / failure criteria
- Critical number of cycles to spalling: number of cycles immediately prior to reaching a 30% ratio of spalling area of the TBC.
- Thermal shock resistance: temperature difference that causes a 30% reduction in tensile adhesive strength relative to the unshocked condition.
- Apparatus and control
- High‑ and low‑temperature baths or furnace plus cooling water bath; thermocouples and temperature controllers for precise control.
- Permissible temperature deviations: room to ≤600 °C ±3 °C; >600 to ≤800 °C ±4 °C; >800 to ≤1 000 °C ±5 °C; >1 000 °C ±7 °C.
- Test pieces
- Flat plate or disk geometries (examples include flat plates 20–100 mm long, 20–50 mm wide, 1.5–12.7 mm thick; disks 20–40 mm diameter, 1.5–5.0 mm thick).
- Measurements and reporting
- Visual and photographic records of spalling and cracking; image analysis to determine spalling area.
- Cross‑sectional microstructural examination and photographic records.
- Use of three or more specimens per condition to determine critical cycle counts.
Applications
- Screening and comparative evaluation of thermal barrier coatings used on hot‑section parts (blades, vanes, combustors) in gas turbines and aero‑engines.
- Assessing TBC durability against thermal cycling, shock events (e.g., emergency shutdown), and TGO (thermally grown oxide) effects.
- Supporting materials selection, process development, failure analysis, and lifetime estimation for coated high‑temperature components.
Who should use this standard
- Coating manufacturers and feedstock suppliers
- Materials and mechanical engineers in aerospace and power generation
- OEMs of gas turbines and aero‑engines
- Independent testing laboratories and R&D groups working on TBC development
Related standards
- ISO 14232 - Thermal spraying - Powders (composition and supply)
- ISO 14916 - Thermal spraying - Determination of tensile adhesive strength
Keywords: ISO 14188:2012, thermal barrier coatings, TBC, thermal cycle resistance, thermal shock resistance, spalling, tensile adhesive strength, thermally grown oxide, TBC testing.
Open preview (PDF)Metallic and other inorganic coatings — Test methods for measuring thermal cycle resistance and thermal shock resistance for thermal barrier coatings
