Heat fatigue test

Heat Fatigue Testing Service – Comprehensive Thermal Cycling and Thermal Shock Evaluation for Materials and Components

As an ISO/IEC 17025 accredited independent testing laboratory, we offer specialised heat fatigue testing services to manufacturers, engineering contractors, and quality assurance teams across the aerospace, automotive, power generation, electronics, and industrial equipment sectors. Heat fatigue – the progressive and localised structural damage that occurs when materials are subjected to repeated thermal cycling and cyclic thermal stresses – is a critical failure mechanism that can lead to cracking, distortion, loss of mechanical properties, and premature component failure. Our heat fatigue test protocols simulate the effects of thermal cycling (heating and cooling), thermal shock (rapid temperature transitions), and dwell‑time‑dependent stress relaxation on metallic and non‑metallic materials, coatings, and assemblies. All methods are aligned with ASTM E606 (Standard Practice for Strain‑Controlled Fatigue Testing), ASTM E466 (Standard Practice for Conducting Force Controlled Constant Amplitude Axial Fatigue Tests of Metallic Materials), ISO 12111 (Metallic materials – Fatigue testing – Strain‑controlled thermomechanical fatigue testing method), IEC 60068‑2‑14 (Environmental testing – Test N: Change of temperature), and GB/T 2423.22 (Environmental testing – Change of temperature test). Our inspection and test reports are recognised by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Industry and Information Technology (MIIT), and international certification bodies for product registration, type approval, and quality assurance.

Test Articles and Component Types We Assess

Our heat fatigue test facilities accommodate a wide range of materials, components, and assemblies. Typical test articles include:

• Metallic materials and alloys – steels, aluminium alloys, titanium alloys, superalloys, and nickel‑based alloys for high‑temperature applications
• Polymer and composite materials – high‑temperature engineering plastics, carbon fibre reinforced polymers (CFRP), and ceramic matrix composites
• Coatings and surface treatments – thermal barrier coatings (TBCs), ceramic coatings, metallic coatings, and protective paint systems
• Aerospace components – turbine blades, combustor liners, exhaust nozzles, and engine casings
• Automotive components – exhaust manifolds, turbocharger housings, brake discs, and engine blocks
• Electronics and electrical components – power modules, printed circuit boards (PCBs), soldered joints, and electrical insulators
• Power generation equipment – boiler tubes, heat exchanger components, gas turbine blades, and steam turbine parts
• Industrial furnace and high‑temperature equipment – furnace linings, heating elements, and thermocouple sheaths

Test Methods – Thermal Cycling, Thermal Shock and Thermomechanical Fatigue

• Thermal cycling test (thermal fatigue) – ASTM E606 / ISO 12111 – for simulating cyclic temperature variations – We expose the test specimen to a defined sequence of heating and cooling cycles between two temperature extremes (e.g., ambient to 800 °C, or 200 °C to 600 °C) at a controlled heating and cooling rate (typically 2‑20 °C/min). The cycle frequency (typically 0.01‑0.1 Hz) and the number of cycles (typically 1 000‑10 000) are selected to simulate the expected service life. The specimen is monitored for crack initiation, crack propagation, and surface degradation. The test can be performed on free‑standing specimens (without mechanical loading) or under a constant or cyclic mechanical load (thermomechanical fatigue).
• Thermal shock test – IEC 60068‑2‑14 / GB/T 2423.22 – for assessing resistance to rapid temperature changes – We subject the specimen to a very rapid temperature transition (typically < 5 seconds) between a hot chamber (e.g., +150 °C) and a cold chamber (e.g., -40 °C) using a two‑chamber transfer system. The dwell time at each temperature (typically 15‑60 minutes) and the number of cycles (typically 5‑500) are determined by the application. The test is used to simulate the thermal stresses experienced during processes such as metal casting, welding, or sudden temperature changes in service.
• Thermomechanical fatigue (TMF) – ASTM E606 / ISO 12111 – for combined thermal and mechanical loading – We simultaneously apply a cyclic mechanical load (tension‑compression, bending, or torsion) and a cyclic temperature profile (in‑phase or out‑of‑phase). The test simulates the combined effect of thermal and mechanical stresses that components experience in service (e.g., turbine blades, exhaust manifolds). The strain or stress amplitude, the temperature range, and the cycle frequency are selected to match the service conditions. The test is performed until failure or until a predetermined cycle count is reached.
• Thermal cycling with dwell – for simulating stress relaxation and creep – We add a dwell period (holding the specimen at the peak temperature for a specified time, e.g., 5‑30 minutes) between the heating and cooling phases. The dwell time accelerates the effects of creep and stress relaxation, which are significant failure modes in high‑temperature components.
• Thermal fatigue under protective atmosphere – for oxidation‑sensitive materials – For materials that are sensitive to oxidation at elevated temperatures, we perform the thermal fatigue test in a controlled atmosphere (argon, nitrogen, or vacuum) to isolate the thermal fatigue effect from the oxidation effect. The test helps to differentiate between thermal damage and oxidation‑driven damage.

Test Specimen Preparation and Instrumentation – Ensuring Representative Results

• Specimen machining and preparation – to standard dimensions and surface finish – We machine the test specimens (typically cylindrical, rectangular, or flat) to the dimensions specified by the test method (e.g., ASTM E466 for axial fatigue, ASTM E606 for strain‑controlled fatigue). The specimen surface finish is controlled to a specified Ra value (typically 0.8‑1.6 µm) to avoid surface‑initiated failures.
• Thermocouple attachment – for precise temperature measurement and control – We attach fine‑wire thermocouples (type K or type T, 0.2‑0.5 mm diameter) to the specimen surface at critical locations (including the test section and the grips) to monitor the temperature during the thermal cycling. The thermocouples are welded (for metals) or attached with high‑temperature ceramic cement (for ceramics and composites).
• Strain measurement – for thermomechanical fatigue tests – For TMF tests, we attach strain gauges (or use an extensometer) to the specimen to measure the strain during the test. The strain data is used to control the test (for strain‑controlled tests) or to monitor the stress‑strain response.
• Heating and cooling methods – induction, resistance, infrared, or furnace – We use a range of heating methods: (a) induction heating – for rapid heating (up to 100 °C/s); (b) resistance heating – for uniform heating of small specimens; (c) infrared heating – for rapid, non‑contact heating; and (d) furnace heating – for slow, uniform heating of large specimens. Cooling is achieved by forced air, water spray, or by moving the specimen to a cold chamber.

Evaluation of Heat Fatigue Damage – Cracking, Oxidation and Property Degradation

• Crack detection and measurement – using dye penetrant, magnetic particle, or eddy current – ASTM E165 / E709 / E426 – After the test, we perform non‑destructive testing (NDT) to detect and measure the length, depth, and distribution of surface cracks. For small cracks (< 1 mm), we use optical microscopy (with a digital camera) and scanning electron microscopy (SEM) for detailed characterisation.
• Oxidation and surface degradation assessment – weight gain/loss and oxide thickness measurement – We measure the weight change (weight gain due to oxidation or weight loss due to spallation) before and after the test. We also measure the oxide layer thickness using metallographic cross‑sectioning and optical microscopy.
• Microstructural examination – for identifying phase transformations, grain coarsening, and precipitate coarsening – ASTM E3 / E407 – We prepare metallographic specimens from the tested material and examine them under an optical microscope (and, where required, SEM and EDS) to detect any microstructural changes induced by thermal cycling, such as the formation of a brittle phase, grain coarsening, or the loss of the strengthening precipitate.
• Mechanical property evaluation after thermal fatigue – tensile and hardness testing – ASTM E8 / E10 / E18 – We perform tensile testing (on a set of un‑exposed specimens) and hardness testing (on the exposed specimens) to quantify the degradation in mechanical properties. The percentage retention of tensile strength, yield strength, and elongation (or hardness) is calculated and reported.
• Fracture surface analysis – for identifying the failure mechanism – ASTM E1508 / ISO 10543 – For specimens that fail during the test, we examine the fracture surface under a stereomicroscope (and, where required, under SEM) to identify the crack initiation site, the propagation direction, and the failure mechanism (e.g., transgranular fatigue, intergranular cracking, or oxidation‑assisted cracking).

Data Analysis and Interpretation – Quantifying Heat Fatigue Performance

• Thermal fatigue life (Nf) – the number of cycles to failure – The thermal fatigue life is the number of thermal cycles that the specimen can withstand before failure (cracking, fracture, or excessive deformation). The Nf is determined from the test data and is used to estimate the component's service life under thermal cycling conditions.
• Thermal fatigue limit – the maximum stress or strain amplitude that the material can withstand for an infinite number of cycles – For materials with a clear endurance limit, we determine the thermal fatigue limit (the stress or strain amplitude that the material can withstand for a specified number of cycles, typically 10⁷ or 10⁸ cycles).
• Crack initiation and propagation rates – for modelling component life – For advanced characterisation, we measure the crack length as a function of the number of cycles to determine the crack initiation time and the crack propagation rate. The data is used for fracture mechanics calculations and for predicting the remaining life of components in service.
• Oxidation kinetics – for predicting high‑temperature degradation – We model the weight gain (due to oxidation) as a function of the number of cycles, using the parabolic rate law (W² = k × t). The oxidation rate constant (k) and the activation energy (Ea) are calculated, and the results are used to predict the oxidation‑induced degradation under different service conditions.
• Statistical analysis – for evaluating batch‑to‑batch consistency – For multiple specimens, we report the mean, standard deviation, and coefficient of variation (CV) of the thermal fatigue life and the crack length. A CV of less than 20 % is typically acceptable for engineering alloys.

Regulatory Compliance and Product Certification – Supporting Industry Standards

Our heat fatigue testing services are performed in accordance with a wide range of national and international standards. The most commonly requested include:

• ASTM E606 – Standard Practice for Strain‑Controlled Fatigue Testing – for strain‑controlled thermomechanical fatigue testing
• ASTM E466 – Standard Practice for Conducting Force Controlled Constant Amplitude Axial Fatigue Tests of Metallic Materials – for force‑controlled fatigue testing
• ISO 12111 – Metallic materials – Fatigue testing – Strain‑controlled thermomechanical fatigue testing method – for thermomechanical fatigue testing
• IEC 60068‑2‑14 – Environmental testing – Test N: Change of temperature – for thermal shock and thermal cycling testing
• GB/T 2423.22 – Environmental testing – Change of temperature test – the Chinese national standard for thermal shock testing
• ISO 204 – Metallic materials – Uniaxial creep testing in tension – for creep testing under temperature and load
• ASTM E139 – Standard Test Methods for Conducting Creep, Creep‑Rupture, and Stress‑Rupture Tests of Metallic Materials – for creep‑rupture testing

Report Acceptance and Regulatory Recognition

All heat fatigue tests are conducted under our ISO/IEC 17025 accreditation, using calibrated environmental chambers, furnaces, and instrumentation, all traceable to national and international reference standards. Our final test reports include: a complete description of the test article (material, dimensions, heat treatment), the test method and conditions (temperature range, heating/cooling rate, dwell time, number of cycles, mechanical load), the measured parameters (thermal fatigue life, crack length, weight change, tensile strength retention, hardness change, oxide thickness), the crack detection and microstructural evaluation results, a statistical summary (mean, standard deviation, CV), and a clear pass/fail verdict against your specified acceptance criteria. These reports are accepted by the National Medical Products Administration (NMPA), the State Administration for Market Regulation (SAMR), the Ministry of Industry and Information Technology (MIIT), and international certification bodies for product registration, type approval, and quality assurance. Bilingual (Chinese/English) versions are available to facilitate submissions to domestic and international authorities and to support your global market access.