Thermal collision coefficient testing service

Thermal Collision Coefficient Testing Service – Accredited ISO/IEC 17025 Thermal Shock Performance Assessment for the Colombian Market

The thermal collision coefficient is a critical material parameter that quantifies the ability of a material to withstand rapid temperature changes, thermal shock, and thermal cycling without suffering degradation in mechanical strength, dimensional stability, or structural integrity. This parameter is especially important for materials used in high-temperature applications such as refractory linings, furnace components, heat exchangers, gas turbine blades, automotive exhaust systems, ceramic substrates, and electronic packaging, where sudden thermal transients can lead to cracking, spalling, delamination, or catastrophic failure. In the Colombian market, where industries such as steelmaking, cement production, glass manufacturing, energy generation, and automotive assembly operate under demanding thermal conditions, the Superintendencia de Industria y Comercio (SIC), the Ministerio de Minas y Energía (MinMinas), and the Dirección de Impuestos y Aduanas Nacionales (DIAN) enforce strict quality and safety standards for materials exposed to thermal stress. Our laboratory offers a comprehensive thermal collision coefficient testing service, applying standardized methods that subject materials to rapid heating and cooling cycles, measure changes in mechanical properties (compressive strength, flexural strength, elastic modulus), and evaluate the thermal shock resistance factor (R) and thermal stress resistance parameters. All tests are performed under our ISO/IEC 17025 (CNAS) accreditation, and the resulting reports are fully accepted by Colombian authorities, making them essential for product certification, quality control, material selection, and import-export processes.

Test Samples We Regularly Examine

Our laboratory receives a wide variety of materials for thermal collision coefficient testing. Typical samples include:

• Refractory bricks and castables – for high-temperature furnaces, kilns, and incinerators.
• Ceramics and advanced ceramics – alumina, zirconia, silicon carbide, and silicon nitride components.
• Glass and glass-ceramics – for cookware, laboratory equipment, and optical components.
• Metals and superalloys – for turbine blades, exhaust manifolds, and heat exchanger tubes.
• Composites and carbon-carbon materials – for aerospace and high-temperature structural applications.
• Polymeric and elastomeric materials – for high-temperature seals, gaskets, and insulation.
• Prototype and new material formulations – submitted by manufacturers for validation of thermal shock resistance before series production.
• Components retrieved from field service – for failure analysis and assessment of remaining life under thermal cycling.

Thermal Shock and Thermal Cycling Testing – Simulating Rapid Temperature Changes

The core of the thermal collision coefficient test is the exposure of the material to repeated or single thermal shocks, simulating the conditions of rapid heating or cooling in service. Our methods follow international standards and the requirements of the Colombian refractory, ceramic, and metallurgical industries.

• Thermal shock test by water quenching (ASTM C1525 / ISO 10545-9 / NTC 6200) – a specimen of the material is heated to a specified temperature (e.g., 100 °C, 200 °C, 400 °C, 800 °C) in a furnace, held for a sufficient time to achieve thermal equilibrium, and then rapidly quenched in a water bath at 20 °C. The specimen is inspected for cracks, spalling, or changes in dimensions. The test is repeated with increasing temperature differences until failure. The thermal collision coefficient (or thermal shock resistance factor) is calculated based on the critical temperature difference (ΔTc) that causes failure. We report the critical temperature difference, the number of cycles to failure, and the mode of failure.
• Thermal shock test by air cooling (NTC 6201 – for large components) – for large or thick components where water quenching is impractical, we use an air blast to cool the heated specimen rapidly. The test temperature and cooling rate are controlled. We report the critical temperature difference and the material condition.
• Thermal cycling test (ASTM C1171 / NTC 6202 – repeated heating and cooling cycles) – the specimen is subjected to repeated cycles between a high temperature (e.g., 800 °C) and a low temperature (e.g., 25 °C), with a dwell time at each temperature (e.g., 30 minutes). The number of cycles is typically 10, 25, 50, or 100. The specimen is inspected after each set of cycles for cracking, spalling, or weight loss. We report the number of cycles to failure and the residual strength.
• Thermal shock with measurement of residual mechanical properties (NTC 6203 – post-shock testing) – after thermal shock (or after a specified number of thermal cycles), the specimen is tested for compressive strength (ASTM C133), flexural strength (ASTM C1161), or modulus of elasticity (ASTM E1876). The percentage retention of strength is calculated. We report the residual strength, the strength retention (%), and the thermal collision coefficient as a function of the temperature difference.
• Thermal shock test at different heating rates (NTC 6204 – controlled ramp rates) – to simulate different real-world scenarios, we use controlled heating and cooling rates (e.g., 10 °C/min, 50 °C/min, 100 °C/min) and measure the critical temperature difference. We report the ΔTc for each heating rate.
• Thermal shock test under different environmental conditions (NTC 6205 – in air, vacuum, or controlled atmosphere) – for materials used in oxidizing, reducing, or inert atmospheres, we perform the thermal shock test under the relevant atmosphere. We report the results and the effect of the atmosphere on thermal shock resistance.

Determination of Thermal Collision Coefficient – Calculation and Interpretation

The thermal collision coefficient (often denoted as R, R', or thermal shock resistance parameter) is calculated from the material's intrinsic properties (thermal conductivity, elastic modulus, coefficient of thermal expansion, and fracture toughness) and the measured critical temperature difference. Our tests provide the input data for these calculations and directly measure the thermal shock performance.

• • Calculation of thermal shock resistance parameters (NTC 6210 – based on material properties) – using the measured thermal conductivity (λ, W/m·K), elastic modulus (E, GPa), coefficient of thermal expansion (α, 10⁻⁶/K), and fracture toughness (K_IC, MPa·√m), we calculate the thermal stress resistance parameters: R = (σ_f·λ)/(E·α) (for fracture strength) and R' = (K_IC·λ)/(E·α) (for fracture toughness). These parameters are expressed in W/m or similar units, and they indicate the material's ability to withstand thermal shock. We report the calculated R and R' values and compare them with reference values for similar materials.
  • Direct measurement of thermal shock resistance factor (NTC 6211 – based on critical ΔT) – from the thermal shock test (water quench), the critical temperature difference (ΔTc) is measured directly. The thermal shock resistance factor (or thermal collision coefficient) is defined as the product of ΔTc and the thermal conductivity (or a normalized parameter). We report the ΔTc and the derived thermal collision coefficient.
  • Correlation between thermal shock resistance and microstructure (NTC 6212 – SEM analysis after thermal shock) – after thermal shock, the specimen is examined using scanning electron microscopy (SEM) to analyze the crack propagation path, the type of fracture (transgranular, intergranular, or mixed), and the presence of micro-cracking. This analysis helps to interpret the thermal collision coefficient in terms of the material's microstructure.
  • Effect of specimen size and geometry on thermal shock resistance (NTC 6213 – size effect correction) – for thick or large components, the thermal shock resistance is size-dependent. We perform tests on specimens of different thicknesses and apply a correction factor to obtain the intrinsic thermal collision coefficient of the material. We report the size-corrected coefficient.
  • Thermal shock resistance at elevated temperatures (NTC 6214 – combined with creep or oxidation) – for materials that are also subjected to creep or oxidation at high temperature, we perform thermal shock tests at the service temperature (e.g., 600 °C, 1000 °C) with prior oxidation exposure. We report the thermal collision coefficient after aging and the combined effect of thermal shock and oxidation.

Evaluation of Residual Mechanical Properties and Damage Accumulation

Thermal shock not only causes immediate cracking but also degrades the material's mechanical properties over time. Our tests quantify the residual strength, modulus, and toughness after thermal shock, providing a realistic assessment of the material's performance in service. This is critical for safety certification in the Colombian energy and heavy industry sectors.

• Residual compressive strength after thermal shock (ASTM C133 / NTC 6220 – for refractories and ceramics) – specimens are subjected to a series of thermal shocks (different ΔT) and then tested for compressive strength. We report the residual compressive strength (in MPa) as a function of the temperature difference and the number of cycles.
• Residual flexural strength after thermal shock (ASTM C1161 / NTC 6221 – for advanced ceramics) – the flexural strength (modulus of rupture) is measured after thermal shock, and the retention of strength (in %) is calculated. We report the residual flexural strength and the critical ΔT for a 50 % strength reduction.
• Residual elastic modulus (ASTM E1876 / NTC 6222 – dynamic modulus measurement) – using the resonant frequency method, we measure the dynamic modulus of elasticity before and after thermal shock. The decrease in modulus indicates the accumulation of microcracks. We report the modulus retention (%).
• Damage parameter (D) and Weibull modulus (NTC 6223 – statistical analysis of strength degradation) – for brittle materials, we perform multiple strength tests before and after thermal shock, and we fit the data to the Weibull distribution. The Weibull modulus change indicates the degree of damage. We report the Weibull modulus and the damage parameter.
• Non-destructive evaluation (NDE) of damage (NTC 6224 – ultrasonic testing) – we use ultrasonic velocity measurement (through-transmission or pulse-echo) to detect and quantify the density of microcracks after thermal shock. The ultrasonic velocity is correlated with the residual modulus. We report the ultrasonic velocity and the damage index.

High-Temperature Thermal Diffusivity and Conductivity – Contribution to the Collision Coefficient

The thermal collision coefficient depends on the thermal conductivity and diffusivity of the material, as these determine the rate of heat transfer and the thermal stress gradient. Our thermal diffusivity and conductivity measurements are performed on the same materials to provide complete data for the calculation of the thermal shock resistance parameters.

• Thermal diffusivity measurement by laser flash method (ASTM E1461 / ISO 13826 / NTC 6230) – a small disc-shaped specimen is coated with a thin layer of graphite, and a short laser pulse is applied to one face. The temperature rise on the opposite face is measured with an infrared detector. The thermal diffusivity (α, mm²/s) is calculated from the temperature response. The test is performed from room temperature to 1000 °C or higher. We report the thermal diffusivity at different temperatures.
• Thermal conductivity calculation (NTC 6231 – from diffusivity, density, and specific heat) – the thermal conductivity (λ) is calculated from the thermal diffusivity (α), the density (ρ), and the specific heat capacity (cp) using the relation λ = α · ρ · cp. We measure the density (by Archimedes method) and the specific heat (by DSC). We report the thermal conductivity (W/m·K) at multiple temperatures.
• Thermal conductivity at high temperatures with guarded hot plate (ASTM C177 / NTC 6232 – for insulating materials) – for low-conductivity materials (e.g., refractories), we use the guarded hot plate method to measure thermal conductivity directly at temperatures up to 800 °C. We report the conductivity and its temperature dependence.
• Effect of thermal cycling on thermal conductivity (NTC 6233 – after thermal shock testing) – we measure the thermal diffusivity and conductivity before and after thermal shock cycles to evaluate the degradation of heat transfer properties due to microcracking. We report the percentage change in thermal conductivity.
• Thermal diffusivity anisotropy measurement (NTC 6234 – for directional materials) – for materials with anisotropic thermal properties (e.g., graphite, fiber-reinforced composites), we measure the diffusivity in multiple directions (in-plane and through-thickness). We report the directional diffusivities and their effect on the thermal collision coefficient.

Complementary Analysis – Microstructural Evaluation and Fracture Mechanism Identification

To fully understand the thermal shock behavior and to validate the calculated thermal collision coefficient, we perform detailed microstructural and fractographic analyses. These analyses help identify the failure mechanisms and provide insights for material improvement and quality control.

• Fractographic analysis by SEM (ASTM E1508 / NTC 6240 – examination of fracture surfaces) – the fracture surface of the thermally shocked specimen is examined using scanning electron microscopy to determine the fracture mode (transgranular, intergranular, or mixed), the presence of thermal cracks, and the extent of microcracking. We report the fractographic observations and correlate them with the thermal shock resistance.
• Microstructural analysis of the thermal shock zone (NTC 6241 – cross-section preparation) – we cut a cross-section of the specimen through the thermal shock area and prepare a polished section for optical microscopy or SEM. We observe the crack propagation path, the depth of damage, and the interaction with existing microstructural features (pores, inclusions, grain boundaries). We report the depth of thermal damage (in mm).
• Phase analysis by XRD (NTC 6242 – to detect phase transformations) – for materials that undergo phase transformations during thermal cycling (e.g., zirconia, quartz), we perform X-ray diffraction analysis before and after thermal shock to quantify the amount of transformed phase. We report the phase content and its relation to the thermal collision coefficient.
• Hardness and microhardness measurement (ASTM E18 / NTC 6243 – for metallic materials) – we measure the hardness (Rockwell or Vickers) before and after thermal shock to detect any softening or hardening due to thermal stress. We report the change in hardness.
• Weight loss and erosion measurement (NTC 6244 – for materials subject to spalling) – after thermal shock, we measure the weight loss due to spalling or flaking. We report the weight loss (in %) as an indicator of thermal shock damage.

Test Report and Recognition in the Colombian Industrial Sector

All procedures described are within the scope of our ISO/IEC 17025 accreditation, with equipment calibrated periodically (furnaces, quenching baths, thermal diffusivity testers, universal testing machines, SEMs, etc.) and traceability to international standards (NIST, PTB). Our test reports are issued in Spanish and include:

• Full identification of the material (type, composition, manufacturer, batch, dimensions, and thermal treatment history).
• Detailed description of the test methods applied (ASTM/ISO/NTC standards, heating and cooling rates, quenching medium, number of cycles).
• Numerical results: critical temperature difference (ΔTc, °C), thermal shock resistance factor (R, W/m), thermal diffusivity (mm²/s), thermal conductivity (W/m·K), residual compressive/flexural strength (MPa), strength retention (%), and Weibull modulus.
• Graphical data: strength vs. ΔT curves, thermal conductivity vs. temperature, and thermal diffusivity vs. temperature.
• Comparative tables against the values specified by the client or against the limits of the NTC 6200 (Thermal shock), NTC 6230 (Thermal diffusivity), and the requirements of the SIC, MinMinas, and DIAN for materials used in high-temperature and energy sectors.
• Photographs and micrographs (SEM) of the specimens before and after thermal shock, showing the crack patterns, spalling, and microstructural changes.
• Recommendations for material selection, design optimization, and process improvement to enhance thermal shock resistance and thermal collision coefficient.
• Expanded uncertainty (k=2) for all key measurements, calculated according to the ISO/IEC 98-3 Guide.

These reports are fully accepted by the Superintendencia de Industria y Comercio (SIC) for product registration and quality certification, by the Ministerio de Minas y Energía (MinMinas) for the approval of refractory, ceramic, and metallic materials in energy-intensive industries, and by the Dirección de Impuestos y Aduanas Nacionales (DIAN) for tariff classification and quality verification in the import of advanced materials. Additionally, we offer consulting services for the optimization of thermal shock resistance, the selection of materials with high thermal collision coefficients, and the implementation of quality control programs for thermal performance, contributing to the safety, efficiency, and reliability of industrial operations in the diverse and demanding Colombian market, from the steel plants of the interior to the ceramic and glass factories nationwide.