BS ISO 20343:2017 pdf download – Fine ceramics (advanced ceramics, advanced technical ceramics) — Test method for determining elastic modulus of thick ceramic coatings at elevated temperature
4 Principle The elevated temperature elastic modulus of ceramic coatings on metal or ceramic substrates is deduced by comparing the elastic moduli of coated and uncoated samples, under the precondition that the interface between the coating and the substrate is continuous and without a debonding zone. The elastic modulus of ceramic coatings can be calculated from three parameters, i.e. the elastic modulus of the uncoated sample or substrate (E s ), equivalent elastic modulus of the coated sample (E q ), and the ratio of the coating thickness to the substrate thickness (R = h/H). The value of E q and E s are determined by the impulse excitation technique.
5 Apparatus
5.1 Elastic modulus testing machine A suitable impulse excitation testing system capable of applying impulses at elevated temperatures shall be used, which shall be in accordance with ISO 17561. Since the test piece is required by ISO 17561 to be homogeneous and isotropic, the measured modulus using the coated test piece is then described as an equivalent elastic modulus.
5.2 Heating system
5.2.1 General The heating system, usually a furnace, shall be capable of heating the test fixture and test piece and maintaining a uniform and constant temperature during the impulse excitation test. The furnace shall have the capability for containing air, inert gas, or a vacuum environment as required for the test.
5.2.2 Temperature stability The furnace shall be controlled by a device capable of maintaining a constant temperature within ±2 °C or better within its working space during the time when the elastic modulus of test pieces is being measured.
5.2.3 Test temperature uniformity The furnace shall be capable of maintaining a uniform test piece temperature. It shall previously be determined that the temperature of the test piece does not vary by more than 0,5 % of the test temperature after a 15 min hold time at the required test temperature measured in °C.
5.2.4 Furnace heating rate The furnace control device shall be capable of maintaining a heating rate of the furnace of 5 °C/min to 10 °C/min and preventing temperature overshoots.
5.2.5 Furnace stability The time for the system to reach thermal equilibrium at the test temperature shall be determined for the test temperature to be used.
5.3 Temperature measuring and indicating instruments
5.3.1 General The thermocouple temperature measuring equipment shall have a resolution of at least 1 °C and an accuracy of 5 °C or better. Optical pyrometers, if used, shall have a resolution of better than 5 °C and an accuracy of 5 °C or better.
5.3.2 Thermocouples Thermocouples in accordance with IEC 60584-1 shall be used. The thermocouple shall exhibit low thermal inertia (the diameter of the wires shall not be greater than 0,5 mm). The measuring thermocouple tip shall be less than 2 mm from the test piece, but never contact the test piece.
5.3.3Thermocouples shall be calibrated periodically against national standards since calibration may drift with usage or contamination. 5.4 Dimension-measuring device A Vernier caliper with a precision of 0,02 mm according to ISO 3611 should be used to measure the dimensions of the test piece. The thickness of the coating shall be measured by using a traceably calibrated optical or scanning electron microscope (SEM) with magnification of 1 000 times or better.
5.5 Test fixture
5.5.1 General The fixture shall be suitable for the installation of the test piece as recommended in ISO 17561 with platinum hanging wires and for impulse excitation and signal acquisition in the furnace. The fixture shall maintain the position of the test piece during the test.
5.5.2The fixture shall be oxidation-resistant if the testing is conducted in air. The fixture shall have negligible chemical reaction with and shall not contaminate the test piece.BS ISO 20343 pdf download.