1、Designation: C664 10 (Reapproved 2015)Standard Test Methods forThickness of Diffusion Coating1This standard is issued under the fixed designation C664; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year of last revision. A nu
2、mber in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.INTRODUCTIONDiffusion coating is a thermally activated means of protecting certain iron, nickel, and cobalt basedalloys against severe operating cond
3、itions. It creates a chemically bonded, tenacious coating that actsas a diffusion barrier against oxygen and other elements into the substrate to provide superioroxidation, corrosion and erosion resistance up to 2100F (1150C). It is commonly used for gasturbine components, power generation component
4、s, and diesel engines. This test procedure providesa mean of determining the thickness of a diffusion coating.1. Scope1.1 These test methods cover two procedures for measuringthe thickness of diffusion coatings.1.2 Test Method A is the determination of the dimensional-change thickness, defined as th
5、e difference in the thickness ofthe part before and after coating. (The terms micrometerthickness and part growth are considered synonymous withdimensional change thickness.)1.3 Test Method B is the determination of total coatingthickness, defined as the distance between the observablyunaffected sub
6、strate and the exterior surface of the coating.This includes the total of all included phases, zones and layers.(The term case depth is considered to be synonymous with totalcoating thickness.) The total coating thickness is determined bycross-sectioning the coating, preparing a metallurgical mounta
7、nd microscopically measuring the coating thickness.1.4 The total coating thickness as determined microscopi-cally from a cross-section will usually be greater than, or equalto, the dimensional change thickness determined by partgrowth. When the coating is produced primarily by reactionwith the subst
8、rate, the substrate-coating interface recedes as thesubstrate is consumed in the reaction. In such cases thedifference between the total coating thickness and the dimen-sional change thickness is the thickness of the substrateconsumed.1.5 Diffusion coatings are usually formed at elevated tem-peratur
9、es for service at elevated temperatures. This means thatdiffusion coatings are dynamic systems which are continuallyundergoing changes while in an elevated-temperature environ-ment. It is necessary to know that certain phases are growing atthe expense of others and to know the previous history of ac
10、oating to understand the significance of coating thicknessdata.1.6 Values in SI units are to be regarded as the standard.Inch-pound units are provided for information only.1.7 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibilit
11、y of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2D374 Test Methods for Thickness of Solid Electrical Insu-lation (Withdrawn 2013)3E3 Guide for Prepar
12、ation of Metallographic Specimens3. Significance and Use3.1 A diffusion coating is one produced by causing anelement or elements to react with or diffuse into, or both, thesurface of a metallic substrate, thus chemically altering thesubstrate adjacent to the surface. To appreciate the significanceof
13、 coating thickness measurements one must understand thecontributions to a particular coating of solid-solution zones inthe substrate and reaction products such as intermetalliccompounds.1These test methods are under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and are the
14、 direct responsibility of SubcommitteeB08.12 on Materials for Porcelain Enamel and Ceramic-Metal Systems.Current edition approved May 1, 2015. Published June 2015. Originallyapproved in 1970. Last previous edition approved in 2010 as C664 87(2010). DOI:10.1520/C0664-10R15.2For referenced ASTM standa
15、rds, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.3The last approved version of this historical standard is referenced onwww.astm.org.Copy
16、right ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States14. Test Method A4.1 ApparatusThe instrument shall be a machinists typemicrometer without a locking device. If calibrated in inches, itshall be constructed with a vernier reading to 0.0001 in
17、. (0.1mil). If calibrated in metric units, it shall be capable of readingto 0.01 mm. It shall have a ratchet or similar mechanism, suchas a friction thimble, for controlling measuring pressure andshall have anvil and spindle surfaces 6.00 6 0.03 mm (0.250 60.001 in.) in diameter. It shall meet all o
18、ther requirements andcalibration procedure for Method A of Test Method D374.4.2 Procedure:4.2.1 Clean the area selected for coating-thickness measure-ment of dust or other powdery materials prior to coating.Record the precise area to be measured, so that the same areacan be remeasured after coating.
19、4.2.2 Take a minimum of two readings, using the machin-ists micrometer, in each area selected. Use the same procedurefor using the micrometer as that stipulated in Test MethodsD374.4.2.3 After the part has been coated and the surface has beencleaned of superficial powder or dirt, repeat the measurem
20、entprocedure. It is necessary to ensure that the same location isremeasured.4.2.4 The thickness of the part after coating minus thethickness of the part prior to coating divided by two, is thedimensional change thickness per coated surface.5. Test Method B5.1 Apparatus:5.1.1 Standard metallurgical s
21、pecimen-preparation equip-ment.5.1.2 Metallographic or optical microscope.5.1.3 The equipment used shall be consistent as to type andquality as specified in Practice E3.5.2 Procedure:5.2.1 Section with a fine grained cut-off wheel the area ofthe coated part in which the total coating thickness is to
22、 bemeasured. Control the clamping of the part, lubricant coolingfluid, and control the cutting rate to produce a square cut edgewithout chipping the coating. Exercise care to ensure that thecut is perpendicular to the surface of the coating.5.2.2 After cleaning with an organic solvent, plate thesect
23、ion (electrolytically or electroless) with nickel, chromium,or other metallic plating which approximates the hardness ofthe coated substrate. As an alternative to plating, wrap thespecimen in a metallic foil. The foil applied must givesufficient support to prevent chipping, and be in sufficientproxi
24、mity to the specimen to prevent gaps and rounding of theedges during polishing.5.2.3 Use the standard techniques detailed in Practice E3 formounting and polishing of the metallurgical specimen.5.2.4 The etching procedure, if required, shall be in generalaccordance with Practice E3. The specific etch
25、ant and etchtime, if employed, will be by mutual agreement between thecustomer and vendor. The etching procedure will clearlydemark the boundaries of the coating as well as properlydifferentiate included zones, if it is desirable to measure theirthickness as well.5.2.5 Measure the total coating thic
26、kness microscopicallywith the aid of a calibrated-filar eyepiece, or by directmeasurement of a projected image on ground glass. Magnifythe coating a minimum of 250 diameters, although 500 ispreferable. When measuring from ground glass, measure theimage of the coating to the closest 1.27 mm (0.05 in.
27、). Theexterior bounds of the coating is the average of the peaks andvalleys. Visually average over a minimum length of 10 mils(0.254 mm (0.010 in.). Determine the interior bounds of thecoating as the depth to which the substrate has been visuallyaltered by the coating. (One must appreciate that this
28、 depth ishighly dependent upon the etchant employed, and mutualagreement of concerned parties should be sought.) As was thecase of the exterior bounds, visually average over a 10 mil(0.254 mm (0.010 in.) length. Measure the specific zones orphases by a mutual agreement between the purchaser and thev
29、endor. Measure the total coating thickness at a minimum of 10locations around the entire metallographic specimen with themeasurement points separated by at least 20 mils (0.508 mm(0.020 in.). Average the individual total coating-thicknessmeasurements.6. Report6.1 The report shall include the followi
30、ng:6.1.1 Thickness as mils per surface. Maximum, minimum,and average of the individual measurements made on a specificpart or specimen.6.1.2 Type of coating thickness determined and the methodemployed,6.1.3 Specific area where the thickness was measured,6.1.4 Type and condition of the coating such a
31、s “as depos-ited” or “after a specified term of service,”6.1.5 If Test Method B is employed, the etching procedure.Aphotomicrograph showing the bounds of a typical area of thecoating is suggested, and6.1.6 If Test Method B is employed, the thickness of anyphases or layers as agreed upon between the
32、purchaser and theseller in mils per surface.7. Precision and Bias7.1 Test Method A (dimensional change thickness) 60.2mil (0.005 mm (0.0002 in.). This test method assumes thatboth sides of surfaces of the coated piece have an equal coatingthickness, if both surfaces are coated. The validity of thisa
33、ssumption will vary with different coatings and processes ofapplication.7.2 Test Method B (total coating thickness)0.1 mil(0.0001 in., 0.0025 mm).C664 10 (2015)2ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this sta
34、ndard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the riskof infringement of such rights, are entirely their own responsibility.This standard is subject to revision at any time by the responsible technical committee and must be revi
35、ewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of this standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsib
36、le technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake your views known to the ASTM Committee on Standards, at the address shown below.This standard is copyrighted by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Co
37、nshohocken, PA 19428-2959,United States. Individual reprints (single or multiple copies) of this standard may be obtained by contacting ASTM at the aboveaddress or at 610-832-9585 (phone), 610-832-9555 (fax), or serviceastm.org (e-mail); or through the ASTM website(www.astm.org). Permission rights to photocopy the standard may also be secured from the Copyright Clearance Center, 222Rosewood Drive, Danvers, MA 01923, Tel: (978) 646-2600; http:/ 10 (2015)3
