1、Designation: C664 10Standard 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 number in parenthese
2、s 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 conditions. It creates
3、 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 components, and diesel engi
4、nes. 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 the difference in th
5、e 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 substrate and the ext
6、erior 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 mountand microscopically
7、 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 substrate, the substrat
8、e-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-peratures for service at
9、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 acoating to understa
10、nd 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 theresponsibility of the user of t
11、his 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-lationE3 Guide for Preparation of Metallographic Specimens3.
12、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 coating thickness measurements one
13、must understand thecontributions to a particular coating of solid-solution zones inthe substrate and reaction products such as intermetalliccompounds.4. Test Method A4.1 ApparatusThe instrument shall be a machinists typemicrometer without a locking device. If calibrated in inches, it1These test meth
14、ods are under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and are the direct responsibility of SubcommitteeB08.12 on Materials for Porcelain Enamel and Ceramic-Metal Systems.Current edition approved April 1, 2010. Published May 2010. Originallyapproved in 1970. Last prev
15、ious edition approved in 2005 as C664 87(2005). DOI:10.1520/C0664-10.2For referenced ASTM standards, 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
16、website.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.shall be constructed with a vernier reading to 0.0001 in. (0.1mil). If calibrated in metric units, it shall be capable of readingto 0.01 mm. It shall have a ratchet or similar m
17、echanism, 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 other requirements andcalibration procedure for Method A of Test Method D374.4.2 Procedure:4.2.1 Clean the area selected f
18、or 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.4.2.2 Take a minimum of two readings, using the machin-ists micrometer, in each area selected. Use the same procedurefor
19、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 measurementprocedure. It is necessary to ensure that the same location isremeasured.4.2.4 The thickness of the part after coating
20、 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 specimen-preparation equip-ment.5.1.2 Metallographic or optical microscope.5.1.3 The equipment used shall be consistent as
21、 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 bemeasured. Control the clamping of the part, lubricant coolingfluid, and control the cutting rate to produce a square c
22、ut 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 thesection (electrolytically or electroless) with nickel, chromium,or other metallic plating which approximates the hardness oft
23、he 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 sufficientproximity to the specimen to prevent gaps and rounding of theedges during polishing.5.2.3 Use the standard techniques detailed
24、 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 etchant and etchtime, if employed, will be by mutual agreement between thecustomer and vendor. The etching procedure will cle
25、arlydemark 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 thickness microscopicallywith the aid of a calibrated-filar eyepiece, or by directmeasurement of a projected image on ground
26、glass. Magnifythe coating a minimum of 2503 diameters, although 5003 ispreferable. When measuring from ground glass, measure theimage of the coating to the closest 1.27 mm (0.05 in.). Theexterior bounds of the coating is the average of the peaks andvalleys. Visually average over a minimum length of
27、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 depth ishighly dependent upon the etchant employed, and mutualagreement of concerned parties should be sought.) As was
28、 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 thevendor. Measure the total coating thickness at a minimum of 10locations around the entire metallographic specimen with t
29、hemeasurement 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 following:6.1.1 Thickness as mils per surface. Maximum, minimum,and average of the individual measurements made on a specificp
30、art 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 as “as depos-ited” or “after a specified term of service,”6.1.5 If Test Method B is employed, the etching procedure.A ph
31、otomicrograph 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 purchaser and theseller in mils per surface.7. Precision and Bias7.1 Test Method A (dimensional change thickness)60.2m
32、il (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 thisassumption will vary with different coatings and processes ofapplication.7.2 Test Method B (total coating thickness)60.1
33、 mil(0.0001 in., 0.0025 mm).C664 102ASTM International takes no position respecting the validity of any patent rights asserted in connection with any item mentionedin this standard. Users of this standard are expressly advised that determination of the validity of any such patent rights, and the ris
34、kof 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 reviewed every five years andif not revised, either reapproved or withdrawn. Your comments are invited either for revision of thi
35、s standard or for additional standardsand should be addressed to ASTM International Headquarters. Your comments will receive careful consideration at a meeting of theresponsible technical committee, which you may attend. If you feel that your comments have not received a fair hearing you shouldmake
36、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 Conshohocken, 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 ASTM website (www.astm.org/COPYRIGHT/).C664 103
