1、raising standards worldwideNO COPYING WITHOUT BSI PERMISSION EXCEPT AS PERMITTED BY COPYRIGHT LAWBSI Standards PublicationBS ISO 13826:2013Metallic and other inorganiccoatings Determination ofthermal diffusivity of thermallysprayed ceramic coatings bylaser flash methodBS ISO 13826:2013 BRITISH STAND
2、ARDNational forewordThis British Standard is the UK implementation of ISO 13826:2013. The UK participation in its preparation was entrusted to TechnicalCommittee STI/40, Thermal spraying and thermally sprayed coatings. A list of organizations represented on this committee can be obtained on request
3、to its secretary.This publication does not purport to include all the necessary provisions of a contract. Users are responsible for its correct application. The British Standards Institution 2013. Published by BSI Standards Limited 2013ISBN 978 0 580 68915 4 ICS 25.220.20 Compliance with a British S
4、tandard cannot confer immunity from legal obligations.This British Standard was published under the authority of the Standards Policy and Strategy Committee on 31 January 2013.Amendments issued since publicationDate T e x t a f f e c t e dBS ISO 13826:2013 ISO 2013Metallic and other inorganic coatin
5、gs Determination of thermal diffusivity of thermally sprayed ceramic coatings by laser flash methodRevtements mtalliques et autres revtements inorganiques Dtermination de la diffusivit thermique des revtements cramiques obtenus par projection thermique par la mthode flash laserINTERNATIONAL STANDARD
6、ISO13826First edition2013-01-15Reference numberISO 13826:2013(E)BS ISO 13826:2013ISO 13826:2013(E)ii ISO 2013 All rights reservedCOPYRIGHT PROTECTED DOCUMENT ISO 2013All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form or by any means
7、, electronic or mechanical, including photocopying and microfilm, without permission in writing from either ISO at the address below or ISOs member body in the country of the requester.ISO copyright officeCase postale 56 CH-1211 Geneva 20Tel. + 41 22 749 01 11Fax + 41 22 749 09 47E-mail copyrightiso
8、.orgWeb www.iso.orgPublished in SwitzerlandBS ISO 13826:2013ISO 13826:2013(E) ISO 2013 All rights reserved iiiContents PageForeword ivIntroduction v1 Scope . 12 Terms and definitions . 13 Principle of test method . 14 Test method . 24.1 General . 24.2 Apparatus 25 Test specimen (disc) . 36 Procedure
9、s 37 Calculation of thermal diffusivity . 48 Test report . 4Annex A (informative) Calculations of thermal diffusivity after appropriate corrections 6Bibliography .11BS ISO 13826:2013ISO 13826:2013(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of nationa
10、l standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. Internation
11、al organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.International Standards are drafted in accordance with the rules
12、given in the ISO/IEC Directives, Part 2.The main task of technical committees is to prepare International Standards. Draft International Standards adopted by the technical committees are circulated to the member bodies for voting. Publication as an International Standard requires approval by at leas
13、t 75 % of the member bodies casting a vote.Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights.ISO 13826 was prepared by Technical Committee ISO/TC 107, M
14、etallic and other inorganic coatings.iv ISO 2013 All rights reservedBS ISO 13826:2013ISO 13826:2013(E)IntroductionThermally sprayed ceramic coatings provide protection against high-temperature corrosion, erosion and wear; they can also change the appearance, electrical or tribological properties of
15、the surface, replace worn material, etc. Thermal barrier coatings (TBCs) are typical examples of such ceramic coatings.Thermal diffusivity data of thermally sprayed ceramic coatings are measured by the laser flash method. The data are used to calculate thermal conductivity when provided with density
16、 and specific heat capacity data.Thermal diffusivity and thermal conductivity are significant properties of such thermally sprayed coatings when designing for thermal insulation, thermal isolation, efficient heat transfer and cooling systems. It is used by designers to calculate appropriate thicknes
17、s needed to protect the metallic components and thus to determine the maximum temperature to which super-alloys with the thermally sprayed ceramic coatings could be exposed.This International Standard gives guidelines for the determination of thermal diffusivity of thermally sprayed ceramic coatings
18、 by the laser flash method. ISO 2013 All rights reserved vBS ISO 13826:2013BS ISO 13826:2013Metallic and other inorganic coatings Determination of thermal diffusivity of thermally sprayed ceramic coatings by laser flash method1 ScopeThis International Standard specifies a test method of thermal diff
19、usivity of thermally sprayed ceramic coatings using laser technology.This test method is applicable to self-standing thermally sprayed ceramic coatings of thickness between 0,8 mm to 2 mm, deposited by various thermal spray processes and removed from the substrate. Thermal diffusivity values ranging
20、 from 107m2/s to 104m2/s are measurable by this test method for temperature range from 300 K to 1500 K.2 Terms and definitionsFor the purposes of this document, the following terms and definitions apply.2.1thermal diffusivityratio of thermal conductivity to specific heat capacity per unit mass, whic
21、h describes the rate at which heat flows through a material, expressed in m2/s2.2half-rise timet1/2time needed for the rear surface temperature to reach one-half of its maximum value or half-rise time, expressed in s3 Principle of test methodThe laser flash method is based on the measurement of the
22、temperature profile of the rear surface of the sample when a pulsed laser illuminates the front surface, thus avoiding interference between the sensor, recording the temperature rise on the rear surface, and heat source.Thermal diffusivity shall be measured by applying a high-intensity short-duratio
23、n heat pulse to one face of a parallel-sided homogeneous test part, monitoring the temperature rise at the opposite face as a function of time, and determining the transient half-rise time (t1/2).1Thermal diffusivity is calculated as=Lt212/(1)where is the thermal diffusivity correction factor;L is t
24、he thickness of the specimen, m;INTERNATIONAL STANDARD ISO 13826:2013(E) ISO 2013 All rights reserved 1BS ISO 13826:2013ISO 13826:2013(E)4 Test method4.1 GeneralThe laser flash method determines the thermal diffusivity for coatings on known substrates using small disc-shaped specimens. Covering an a
25、pplication range from 300 K to 1500 K, it fulfils the needs of thermal classification for almost any material and system problem, including ceramic thermal barrier coatings. The laser flash method is currently the most widely accepted method for precise measurement of the thermal diffusivity.24.2 Ap
26、paratusThe essential features of a laser flash diffusivity unit are shown in Figure 1.Key1 Laser2 Vacuum or inert atmosphere3 Sample4 Heater5 Detector6 AD-converter and amplifier7 Digital Data Acquisition System8 Printer9 PC10 Visual DisplayFigure 1 Schematic diagram of laser flash diffusivity unitT
27、he window is of any transparent material and the specimen holder is ceramic or any other material with lower thermal conductivity than the sample.4.2.1 Flash sourceIt is essential for the laser source to be uniform over the entire surface of the specimen. For this reason, Neodymium (Nd) glass laser
28、as a flash source is preferred. The pulse width, FWHM (full width at half maximum), should be shorter than 1,0 ms.2 ISO 2013 All rights reservedBS ISO 13826:2013ISO 13826:2013(E)4.2.2 HeaterThe heater shall be of adequate dimension to heat and fix within the temperature range. It shall be capable of
29、 having a suitable temperature control facility prior to and during a test to be less than 4 % of the maximum temperature rise.4.2.3 Environmental control cabinetThe cabinet, capable of measuring below and above room temperature, may be a vacuum chamber or contain inert gas for operation in a protec
30、tive atmosphere and is fitted with a window, which is transparent to the flash source. A second window for detection of the rear surface temperature rise shall be transparent. The optical detector shall be shielded from direct exposure to the energy beam with appropriate filters.4.2.4 Detector and s
31、ignal conditioningFor the measurement of thermal diffusivity, a non-contact infrared type sensor is preferable. However, detectors may consist of thermocouples, optical pyrometers, infrared types, etc. that will provide a linear electrical output proportional to a small temperature rise, capable of
32、sensing a 0,05 C change in temperature. The detector and its associated amplifier shall have a response time substantially smaller than 2 % of the half-rise time value.The signal processor includes the electronic circuit to bias out the ambient temperature reading, spike filters, amplifiers, and ana
33、log-to-digital converters.4.2.5 Data acquisition systemThe response frequency of the data acquisition system should preferably be faster than about 1 MHz per channel and should have a resolution of A/D converter more than 12 bit.5 Test specimen (disc)The optimum thickness of specimens depends on the
34、 magnitude of the thermal diffusivity of the coating. For low thermal diffusivity, the thickness of the specimen is approximately 1 mm; however, for high thermal diffusivity of the coating, a thick sample is used.The typical specimens for the determination of thermal diffusivity are thin circular di
35、scs of 10 mm in diameter and between 0,8 mm to 2 mm in thickness. Faces of specimens shall be flat and parallel within 0,5 % of their thickness.3Non-uniformity of surfaces is to be avoided to prevent errors in the measurement of average thicknesses which gives errors in thermal diffusivity data.For
36、the separation of the coating, either the substrate is prepared with NaCl on the substrate prior to coating by immersing in water to remove the coating, or the coating is applied on a graphite substrate which is then heated to 1000 K for 1 h for removal of the coating.Mostly, specimens are coated on
37、 the front, and at the rear face if an infrared detector is used to check temperature rise, with an opaque or non-reflective film of platinum, nickel, copper, gold or colloidal graphite. These deposits, between 5 m to 10 m, shall not react with the specimen or melt or vaporize over a specified tempe
38、rature range.6 ProceduresThe following preparation procedures of the specimens shall be carried out.a) Record mass, dimensions and density of test specimen.b) Mount it in a sample holder, set up a vacuum or inert gas atmosphere. ISO 2013 All rights reserved 3BS ISO 13826:2013ISO 13826:2013(E)c) Reco
39、rd the specimen temperature and irradiate the test part with a laser beam. Monitor the base line and transient-rise and cooling data to determine maximum temperature rise, given as TmT, where mT is the maximum temperature, in K. Assess the half time, t1/2value from the initiation of the pulse for th
40、e rear-face temperature to reach the half-maximum amount.d) Calculate the heat loss calculation factor h, finite pulse time effect factor, fand thermocouple response time-effects correction factor cfrom the temperature rise data (see Annex A for calculation of correction factors).e) Change the speci
41、men temperature to next value and repeat the tests at different temperatures to obtain appropriate data.7 Calculation of thermal diffusivityFollowing Formula (1) and half-rise time, t1/2from Figure 2, calculate the thermal diffusivity taking into account heat loss correction, finite pulse time-effec
42、ts correction and thermocouple response time-effects correction given in Annex A.Key pulse timet1/2half-rise timeTmtemperature difference between line and maximum rise in temperaturetheoretical maximum riseX time/sY temperature/KFigure 2 Temperature rise as a function of timeThermal diffusivity is a
43、ble to be calculated using other analysis methods, for example, half-rise time method without correction and curve fitting method. The user should report in detail if they use another analysis method instead of Annex A.8 Test reportThe test report shall contain following information:a) a reference t
44、o this International Standard;b) name and address of the testing organization;4 ISO 2013 All rights reservedBS ISO 13826:2013ISO 13826:2013(E)c) date of the test;d) description of the material of test specimen;e) mass, dimensions of the test specimen, reference sample (sapphire) and glassy carbon;f)
45、 calculated value of bulk density;g) laser pulse source;h) environmental conditions;i) specimen temperature (C) and type of temperature rise detector;j) recorded value of the maximum temperature rise, TmTand the half-maximum temperature rise time, t1/2;k) calculated values of thermal diffusivity at
46、each measured temperature;l) statistical results of repeated measurements at each temperature;m) any additional observations concerning the test. ISO 2013 All rights reserved 5BS ISO 13826:2013ISO 13826:2013(E)Annex A (informative) Calculations of thermal diffusivity after appropriate correctionsA.1
47、 GeneralFor the measurement of thermal diffusivity from Formula (1),=Lt212/where is the thermal diffusivity correction factor;L is the thickness of the specimen, m.the following corrections are required.A.1.1 Heat loss correctionHeat loss due to vacuum in the control cabinet is primarily due to radi
48、ation heat exchange.4The relationship between the temperature rise and thermal diffusivity is described using Formula (A.1):TT YYLtLnn nn=() ()exp0221(A.1)whereTQCLp=; YxHxLHxLnnnnnn()cossin/=+()+222122 HHHHH Hnn22222()+()+(); HhLk= ; nHtgH222()= ; n = 1, 2, 3, 4 whereQ is the heat quantity, J;L is
49、the thickness of the specimen, m.6 ISO 2013 All rights reservedBS ISO 13826:2013ISO 13826:2013(E)If there is no heat loss, i.e. h = 0, Formula (A.1) can be described asTTntLnn=+()=12 122021exppi(A.2)If there is heat loss (h 0) during the measurement procedure, Formula (A.1) can be plotted as Figure A.1 with T5t1/2, the rear-face temperature rise after 5t1/2. Figure A.1 shows the relationship between T5t1/2an
