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ASTM C664-10(R2020) pdf free download

ASTM C664-10(R2020) pdf free download.Standard Test Methods for Thickness of Diffusion Coating
1. Scope
1.1 These test methods cover two procedures for measuring the thickness of diffusion coatings. 1.2 Test Method A is the determination of the dimensional- change thickness, defined as the difference in the thickness of the part before and after coating. (The terms micrometer thickness and part growth are considered synonymous with dimensional change thickness.) 1.3 Test Method B is the determination of total coating thickness, defined as the distance between the observably unaffected substrate 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 total coating thickness.) The total coating thickness is determined by cross-sectioning the coating, preparing a metallurgical mount and 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 equal to, the dimensional change thickness determined by part growth. When the coating is produced primarily by reaction with the substrate, the substrate-coating interface recedes as the substrate is consumed in the reaction. In such cases the difference between the total coating thickness and the dimen- sional change thickness is the thickness of the substrate consumed. 1.5 Diffusion coatings are usually formed at elevated tem- peratures for service at elevated temperatures. This means that diffusion coatings are dynamic systems which are continually undergoing changes while in an elevated-temperature environ- ment. It is necessary to know that certain phases are growing at the expense of others and to know the previous history of a coating to understand the significance of coating thickness data.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 the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appro- priate safety, health, and environmental practices and deter- mine the applicability ofregulatory limitations prior to use. 1.8 This international standard was developed in accor- dance with internationally recognized principles on standard- ization established in the Decision on Principles for the Development of International Standards, Guides and Recom- mendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
4. Test Method A
4.1 Apparatus—The instrument shall be a machinist’s type micrometer without a locking device. If calibrated in inches, it shall be constructed with a vernier reading to 0.0001 in. (0.1 mil). If calibrated in metric units, it shall be capable of reading to 0.01 mm. It shall have a ratchet or similar mechanism, such as a friction thimble, for controlling measur- ing pressure and shall have anvil and spindle surfaces 6.00 6 0.03 mm (0.250 6 0.001 in.) in diameter. It shall meet all other requirements and calibration 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 area can be remeasured after coating. 4.2.2 Take a minimum of two readings, using the machin- ist’s micrometer, in each area selected. Use the same procedure for using the micrometer as that stipulated in Test Methods D374. 4.2.3 After the part has been coated and the surface has been cleaned of superficial powder or dirt, repeat the measurement procedure. It is necessary to ensure that the same location is remeasured. 4.2.4 The thickness of the part after coating minus the thickness of the part prior to coating divided by two, is the dimensional change thickness per coated surface.

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