1、Designation: F1854 09F1854 15Standard Test Method forStereological Evaluation of Porous Coatings on MedicalImplants1This standard is issued under the fixed designation F1854; the number immediately following the designation indicates the year oforiginal adoption or, in the case of revision, the year
2、 of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method covers stereological test methods for characterizing the coating thickness, void content, and mea
3、n interceptlength of various porous coatings adhering to nonporous substrates.1.2 A method to measure void content and intercept length at distinct levels (“tissue interface gradients”)(“Tissue InterfaceGradients”) through the porous coating thickness is outlined in 9.4.1.3 The alternate sample orie
4、ntation method in 8.2 is not suitable for the tissue interface gradients method in 9.4.1.3 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.1.4 This standard does not purport to address all of the safety concerns, if any, assoc
5、iated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatorylimitations prior to use.2. Referenced Documents2.1 ASTM Standards:2E3 Guide for Preparation of Metallographic SpecimensE883 Guid
6、e for ReflectedLight Photomicrography3. Terminology3.1 Definitions:Definitions of Terms Specific to This Standard:3.1.1 fieldthe portion of image of a partportion of the working surface upon which measurements are performed.3.1.2 interceptthe point on a measurement grid line projected on a field whe
7、re the line crosses from solid to void or vice versa.3.1.3 measurement grid linesaan evenly spaced grid of parallel lines all of the same length.3.1.4 porous coatingcoating on an implant deliberately applied to contain void regions with the intent of enhancing thefixation of the implant.3.1.5 substr
8、atethe solid material to which the porous coating is attached.3.1.6 substrate interfacethe region where the porous coating is attached to the substrate.3.1.7 working surfacethe ground and polished face of the metallographic mount where the measurements are made.3.1.7 tissue interfacethe surface of t
9、he coating that shall have first contact with biological tissue (that is, (i.e., the top of thecoating).3.1.8 working surfacethe ground and polished face of the metallographic mount where the images of the fields are captured.4. Summary of Test Method4.1 Mean Coating ThicknessEvenly spaced parallel
10、grid lines are oriented perpendicular to the coating-substrate interface.interface on a field. For each gridline, the distance from the coating-substrate interface to the last contact with the porous coating1 This test method is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Ma
11、terials and Devices and is the direct responsibility of SubcommitteeF04.15 on Material Test Methods.Current edition approved June 15, 2009March 15, 2015. Published August 2009May 2015. Originally approved in 1998. Last previous edition approved in 20012009 asF1854 01.F1854 09. DOI: 10.1520/F1854-09.
12、10.1520/F1854-15.2 For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.This document is not an ASTM standard and
13、 is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Becauseit may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only t
14、he current versionof the standard as published by ASTM is to be considered the official document.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States1material is measured as the coating thickness. The average of all of the coating thicknes
15、s measurements obtained on a workingsurface from all the measured fields is the mean coating thickness for that working surface. coating.4.2 Volume Percent VoidA regular grid of points is superimposed on a field from the working surface. The percentage of pointsthat are in contact with void areas in
16、 the coating correlates with is the volume percent of void present.present in that field.4.3 Mean Void Intercept LengthMeasurement grid lines are oriented parallel to the substrate interface. interface in a field. Theaverage length of the line segments overlaying the void space is the mean void inte
17、rcept length. length for that field. This is arepresentative measure of the scale, or size, of the pores in a porous structure.4.4 Tissue Interface GradientsThe volume percent voidVolume Percent Void and the mean void intercept lengthMean VoidIntercept Length are characterized in three 200-m-thick z
18、ones below the tissue interface.Tissue Interface in each field.5. Significance and Use5.1 All of these test methods are recommended for elementary quantification of the morphological properties of porous coatingsbonded to solid substrates.5.2 These test methods may be useful for comparative evaluati
19、ons of different coatings or different lots of the same coating.5.3 With the exception of using the alternate mounting method, all the All the methods should be performed on the sameworking surfaces. The alternate mounting method can only be used for set of images of fields.9.2 and 9.3.5.4 A statist
20、ical estimate can be made of the distributions of the mean coating thickness and the volume percent void. Noestimate can be made of the distribution of intercept lengths.5.5 There are limits to the accurate characterization of porosity, depending on spacing between the lines in the line grid (orpoin
21、ts in the point grid) and the individual and cumulative fields used for the measurements. Increasing the size of the fields,increasing the number of fields, or decreasing the grid spacing will increase the accuracy of the measurements obtained.5.6 This method is notmay be suitable for ceramic coatin
22、gs for whichif an accurate coating cross sections cannot be producedusing section can be produced. Producing an accurate ceramic coating cross section may require other techniques than standardmetallographic techniques.5.7 This test method does not address characterization of For coatings having a m
23、ean thickness of less than 300 m.microns,it is not recommended to attempt to determine the volume percent void or the mean intercept length.6. Apparatus6.1 The procedures outlined in this test method can be performed manually or using digital image analysis techniques.6.2 Microscope, or other suitab
24、le device with a viewing screen, photomicrographic capability, or digital image capturecapability should be used to image the sample fields of interest for these test methods.6.3 For manual measurement, a transparent sheet, with measurement grid lines or points is superimposed on the viewing screeno
25、r photomicrograph for the measurements. The line grid (or point grid) and should consist of at least five uniformly spaced, parallellines (or rows).7. Metallography7.1 The procedures outlined in this test method for characterizing porous coatings require the preparation of metallographicsections. Go
26、od metallographic preparation techniques, in accordance with PracticeGuides E3 and Guide E883, shall be used toprevent deformation of the surface of the section or creation of any other artifacts that will alter the morphology of themetallographic section. An example of an unacceptable artifact woul
27、d be the absence of a portion of the porous coating, causedby its removal, thereby creating an artificial void area.7.2 Care mustshall be taken to ensure that the working surface is perpendicular to the substrate interface. When using thealternative mounting method shown in 8.1.2, extreme care must
28、be taken to keep the substrate interface parallel to the final workingsurface.8. Sample Working Surfaces and Fields8.1 Sample Orientation:8.1.1 Normal Section Orientation:8.1.1.1 For accurate coating thickness measurements, the orientation of sample working surfaces should be approximatelyperpendicu
29、lar to the plane of the substrate.8.1.1.2 If the angle between the tangent to the coating-substrate interface at one edge of a field and the tangent to the substrateinterface at the opposite edge of the field is greater than 2, the substrate curvature is too large.8.1.1.3 There is a practical limit
30、to the magnification that can be used for measurement of the void content and mean interceptlength. As magnification is increased, the number of fields should be increased to obtain a representative sample. If there are toofew intercepts in the individual fields, the accuracy of the measurement coul
31、d decrease.F1854 1528.1.2 Alternative Orientation Method:8.1.2.1 An alternate orientation may be used for the volume percent void and mean intercept length measurements. The sectionshould be prepared such that the working surface is parallel to the substrate interface and the measurements should be
32、taken at afixed distance from the substrate interface. It is recommended that the measurements be made at about 50 % of the mean coatingthickness.8.1.2.2 At least one additional section immediately adjacent to the fields used on the working surface shall also be preparedperpendicular to the working
33、surface. This shall confirm that the substrate interface is parallel to the working surface and allowmeasurement of the distance from the working surface to the substrate interface.8.1.2.3 This test method is not suitable for substrate interfaces with a radius of curvature less than 25 mm.8.1.2.4 Si
34、nce this test method also requires more aggressive porous surface removal to reach 50 % of the mean coatingthickness, it may be more susceptible to creation of metallographic artifacts. Care should be exercised to ensure that themetallographic sections that are used are free of artifacts.8.2 Field P
35、arameters:8.2.1 Resolution:8.2.1.1 The magnification used for the field should be high enough to resolve all the features that need to be measured.8.2.1.2 For most porous coatings, the magnification should be high enough that features as small as 5 m can be easilydistinguished. If digital imaging is
36、 used, the pixel size should be less than or equal to 5 m.8.2.1.3 For digital images the pixel size in m and the image field size in pixels shall be included with the images.8.2.2 Field Dimensions:8.2.2.1 The field height must include the full thickness of of the images shall be large enough to incl
37、ude all the features of anyportion of the porous coating for mean coating thickness (Mean Coating Thickness determination (section 9.1).8.2.2.2 A good rule of thumb for an accurate measurement of mean void intercept lengthMean Void Intercept Length is that theminimum field width should be greater th
38、an or equal to 5 5 times the resulting mean void intercept length.Mean Void InterceptLength. For example, a mean void intercept lengthMean Void Intercept Length value of 200 m should have a measurement fieldwidth of at least 1000 m.8.2.2.3 It is possible to measure the mean void intercept lengthMean
39、 Void Intercept Length in a field using a series of shorternon-overlapping grid lines. This does not change the requirement for the number of fieldscoating field length required for thecalculation. Care should be exercised using multiple short lines in a single field, because it may be is possible t
40、o make the gridlines so short that the accuracy of the result is affected.8.2.2.4 If the magnification used produces an image with a height or width smaller than that which is required, multiple imagesmay be carefully stitched together to produce a field of sufficient height and width.8.2.2.5 All fo
41、ur types of measurements shall be performed over a minimum coating area of 15 mm2 with no area being measuredmore than once. For thinner coatings that require higher magnifications to allow reasonable measurements the minimum totalmeasured field length shall be 20 mm with no part of that length bein
42、g measured more than once.9. Procedure9.1 Mean Coating Thickness:9.1.1 An array of equally spaced parallel gridlines should be superimposed on the field perpendicular to the substrate interface,as shown in Fig. 1. The gridlines should be spaced no more than 100 m apart. Appendix X2 includes two typi
43、cal sets of gridlineseach with ten equally spaced parallel lines.9.1.2 At each gridline, the distance from the substrate interface to the last contact with a solid coating feature is measured. Ameasurement is only valid if the gridline is oriented 9090 6 2 to the substrate interface.NOTE 1The solid
44、line is the measured distance.FIG. 1 Illustration of Coating Thickness MeasurementF1854 1539.1.2.1 The surface of the substrate is usually rough due to the processing involved in applying the coating. If the surface is toorough, a line indicating a subjective average substrate interface shall be mad
45、e on the each field. Thickness measurements shall thenbe made from this line.9.1.2.2 If a subjective average interface line is used, the same line should be used for the positioning of the other measurementsin this standard.9.1.3 Coating thickness measurements should be obtained over a continuous li
46、near distance of at least 1020 mm of poroussurface with no overlap between measurement sites.9.1.4 The average of all the measurements individual coating thickness measurements from all the fields that were measuredis the mean coating thickness for that working surface. thickness. The standard devia
47、tion estimator and the 95 % 95 % confidenceinterval should be calculated for each working surface.all the fields. The equations for calculating these values are as follows:T 5 1M 3n (i51nti (1)where:ti = the individual magnified thickness line length,n = the number of thickness measurements,M = the
48、magnification, andT = the mean coating thickness.S 5 1n 213(i51n F tiM 2TG (2)S 5 1n 213(i51n F tiM 2TG 2 (2)where: = the standard deviation estimator, andCI = the confidence interval.CI523 S=n (3)9.1.5 Define the Tissue Interface of the porous coating.9.1.5.1 The first method to define the location
49、 of the Tissue Interface is a physical one. Securely attach a flat metallic surfaceon the porous interface of the metallographic sample prior to embedding the sample. The attached flat metal surface must showthat it has not moved away from the Tissue Interface during the metallographic mounting process and shall have an angle awayfrom the substrate of less than 1.NOTE 1Spring-loaded binder clips have been used to secure the attached flat metal plate to the tissues interface.9.1.5.2 The second method is to use the average of the longest 5%
