1、Designation: B 650 95 (Reapproved 2008)Standard Specification forElectrodeposited Engineering Chromium Coatings onFerrous Substrates1This standard is issued under the fixed designation B 650; the number immediately following the designation indicates the year oforiginal adoption or, in the case of r
2、evision, the year 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.This standard has been approved for use by agencies of the Department of Defense.1. Scope1.1 This specificati
3、on covers the requirements for electrode-posited chromium coatings applied to ferrous alloys for engi-neering applications.1.2 Electrodeposited engineering chromium, which is some-times called “functional” or “hard” chromium, is usuallyapplied directly to the basis metal and is much thicker thandeco
4、rative chromium. Engineering chromium is used for thefollowing:1.2.1 To increase wear and abrasion resistance,1.2.2 To increase fretting resistance,1.2.3 To reduce static and kinetic friction,1.2.4 To reduce galling or seizing, or both, for various metalcombinations,1.2.5 To increase corrosion resis
5、tance, and1.2.6 To build up undersize or worn parts.1.3 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of
6、 regulatory limitations prior to use.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusB 177 Guide for Engineering Chromium ElectroplatingB 183 Practice for Preparation of Low-Carbon Steel forElectroplatingB 242 Guide for Preparation of High-Carbon Stee
7、l forElectroplatingB 320 Practice for Preparation of Iron Castings for Electro-platingB 374 Terminology Relating to ElectroplatingB 487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination of CrossSectionB 499 Test Method for Measurement of Coating Thick-nesse
8、s by the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis MetalsB 504 Test Method for Measurement of Thickness of Me-tallic Coatings by the Coulometric MethodB 507 Practice for Design ofArticles to Be Electroplated onRacksB 568 Test Method for Measurement of Coating Thicknessby X-Ray Spectrome
9、tryB 571 Practice for Qualitative Adhesion Testing of MetallicCoatingsB 602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB 697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic CoatingsB 762 Test Method of Variables Sampling of Meta
10、llic andInorganic CoatingsB 849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen EmbrittlementB 850 Guide for Post-Coating Treatments of Steel for Re-ducing the Risk of Hydrogen EmbrittlementD 3951 Practice for Commercial PackagingE8 Test Methods for Tension Testing of
11、Metallic MaterialsF 1459 Test Method for Determination of the Susceptibilityof Metallic Materials to Hydrogen Gas Embrittlement(HGE)2.2 Other Standard:MIL-S-13165 Shot Peening of Metal Parts33. Terminology3.1 Definitions:3.1.1 significant surfacesall surfaces upon which a de-posit of controlled thic
12、kness is required.1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.08.01 on Engineering Coatings.Current edition approved Aug. 1, 2008. Published September 2008. Originallyapproved in 1978. Last
13、previous edition approved in 2002 as B 650 95 (2002).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 website.3Availab
14、le from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.3.1.1.1 DiscussionWhen a controlled deposit is requiredin hole
15、s, corners, recesses, and similar areas, special racking,auxiliary anodes or shielding, or both, will be necessary. Withthe best practices there will be areas where a controlled depositis impossible.3.2 Definitions used in this specification are in accordancewith Terminology B 374.4. Classification4
16、.1 Electrodeposited chromium coatings in accordance withthis specification are classified by the thickness of the coatingas follows:Class No. Chromium Thickness, m Typical Application1 2.5 to 25 reduce friction; anti-galling, lightwear resistance2 25 as specified buildup to dimension specified forsa
17、lvage or as required for severewear resistance4.2 Unless otherwise specified by suitably marked drawingsor samples, only those surfaces that can be touched with a20-mm diameter ball shall be considered significant. In holes,corners, recesses, and other areas where a controlled depositcannot be obtai
18、ned under normal electroplating conditions, thethickness of the deposit may be that which results from controlon the significant surfaces.5. Ordering Information5.1 The purchaser shall exercise the desired options of thisstandard. Ordering documents shall specify the followinginformation:5.1.1 Title
19、, ASTM designation, and issue date of this speci-fication,5.1.2 Alloy and metallurgical condition of the product to bechromium plated,5.1.3 Ultimate tensile strength of the material to be plated,5.1.4 Heat treatment required for stress relief and whether ithas been performed or is required,5.1.5 The
20、 significant surfaces if different from the 20-mmball rule (see 3.1.1),5.1.6 Thickness of the deposit or class (see 4.1),5.1.7 Control record requirements,5.1.8 Preproduction test specimens, if required,5.1.9 Sampling plan, if different from that specified in TestMethod B 602 (see Section 8),5.1.10
21、The number of test specimens for destructive testing(see 7.1),5.1.11 Thickness, adhesion, porosity, and hydrogen em-brittlement tests required (see Section 6),5.1.12 Whether separate test specimens will be used (see 7.1and 7.5),5.1.13 Where required, any special requirements for partsthat are subseq
22、uently ground to size,5.1.14 Where required, the base metal finish in terms ofcenter line average (CLA) or arithmetic average (AA), and5.1.15 Where required, dimensional tolerances allowed forthe specified coating thickness or class.5.2 The manufacturer of the parts to be electroplated shallprovide
23、the electroplating facility with test specimens (seeSection 7) to be electroplated for conformance tests as re-quested for preparation, control, inspection, and lot acceptanceunless other arrangements have been made between the pur-chaser and the electroplating facility.6. Coating Requirements6.1 Th
24、e appearance of the chromium coating on the signifi-cant surfaces of the product shall be smooth and free of visualdefects such as blisters, pits, roughness, cracks, burned depos-its, uncoated areas, or macrocracking of the deposit that isvisible without magnification. The boundaries of electroplati
25、ngthat cover only a portion of the surface shall, after finishing asindicated on the drawing, be free of beads, nodules, jaggededges, or other irregularities that will interfere with thefunctioning of the plated part. Imperfections and variations thatarise from surface conditions of the basis metal
26、(scratches,pores, roll marks, inclusions, etc.) and that persist in the finishdespite the observance of good metal finishing practices shallnot be cause for rejection.NOTE 1Applied finishes generally perform better in service when thesubstrate over which they are applied is smooth and free of torn m
27、etal,inclusions, pores, and other defects. It is recommended that the specifi-cations covering the unfinished product provide limits for these defects. Ametal finisher can often remove defects through special treatments such asgrinding, polishing, abrasive blasting, chemical treatments, and elec-tro
28、polishing, which are not normal in the treatment steps preceding theapplication of the finish and will add to the cost. When they are desired,they are the subject of a special agreement between the purchaser and theseller.6.2 In cases where design for maximum fatigue life is aconsideration the parts
29、 should be shot peened (see MIL-S-13165C) or given an alternate mechanical treatment to com-pressively stress the surface.6.3 Stress Relief Treatment (See headnote at the beginningof this specification.):6.3.1 All steel parts having an ultimate tensile strength of1000 MPa (150 000 psiapproximately 3
30、2 HRC) or greater,that may contain residual stress caused by various fabricationoperations such as machining, grinding, straightening, or coldforming, will require one of the stress relief heat treatmentsprescribed in Specification B 849 prior to electroplating. In allcases, the duration of heat tre
31、atment shall commence from thetime at which the whole of each part attains the specifiedtemperature.6.3.1.1 The treatment selected, of necessity, must be basedupon experience with the part or empirical test data. Therefore,Class SR-0 treatment is provided for parts that the purchaserwishes to exempt
32、 from treatment. However, many, if not most,steels with a tensile strength in excess of 1000 MPa willbecome embrittled when plated with chromium. The stressrelief and hydrogen embrittlement relief treatments are essen-tial for the safe performance of chromium plated itemsfabricated from those steels
33、. Selection of Class SR-0 or ER-0requires thorough knowledge of the embrittlement susceptibil-ity of the specific steel employed. When the purchaser specifiesClass SR-0 or ER-0, the purchaser assumes sole responsibilityfor any embrittlement failure of the part. The relative suscep-tibility of a stee
34、l can be determined by subjecting it to the DiskB 650 95 (2008)2Rupture Test of Test Method F 1459. When no stress relieftreatment is specified by the purchaser then Class SR-1 shall beapplied.6.3.2 Parts having surface hardened areas that would sufferan unacceptable reduction in hardness by treatme
35、nt in accor-dance with Specification B 849 shall be heat-treated at a lowertemperature but not less than 130C for a minimum period of8 h. This treatment is applicable for parts made of steel with anactual tensile strength below 1400 MPa. The purchaser mayrequire that the heat-treatment temperature s
36、hall not reduce thesurface hardness. Shorter times at higher temperatures may beused, if the resulting loss of surface hardness is acceptable.6.3.3 If stress relief is given after shot peening or other coldworking processes to introduce beneficial compressivestresses, the temperature shall not excee
37、d 230C.6.4 Hydrogen Embrittlement Relief:6.4.1 Heat treatment appropriate for the tensile strength ofthe electroplated part (see Specification B 850) shall be per-formed to reduce the risk of hydrogen embrittlement. In allcases, the duration of the heat treatment shall commence fromthe time at which
38、 the whole part attains the specified tempera-ture. See 6.3.1.1 for important embrittlement relief informationregarding the selection of ER-0. When no embrittlement relieftreatment is specified by the purchaser then Class ER-1 shall beapplied.6.4.2 Begin the embrittlement relief heat-treatment as so
39、onas practical following the plating process but no longer than 1.5h.6.4.3 Parts or representative specimens shall be tested forcompliance in accordance with 7.5.6.5 ThicknessThe thickness of the coating everywhere onthe significant surface(s) shall conform to the requirements ofthe specified class
40、as defined in Section 3 (see 7.2).NOTE 2The coating thickness requirements of this specification are aminimum requirement, that is, the coating thickness is required to equal orexceed the specified thickness everywhere on the significant surfaces (see4.1). Variation in the coating thickness from poi
41、nt to point on a coatedarticle is an inherent characteristic of electroplating processes. Therefore,the coating thickness must exceed the specified value at some point on thesignificant surfaces to ensure that the thickness equals or exceeds thespecified value at all points. Hence, in most cases, th
42、e average coatingthickness on an article will be greater than the specified value; how muchgreater is largely determined by the shape of the article (see PracticeB 507) and the characteristics of the electroplating process. In addition,the average coating thickness on articles will vary from article
43、 to articlewithin a production lot. Therefore, if all of the articles within a productionlot are to meet the thickness requirement, the average coating thickness forthe production lot as a whole will be greater than the average necessary toensure that a single article meets the requirement. This may
44、 not apply toparts that are ground after plating.6.6 AdhesionThe coating shall be sufficiently adherent tothe basis metal to pass the adhesion test specified (see 7.3).These tests are, with the possible exception of the heat quenchtest, all destructive and therefore, in most cases, should beperforme
45、d on test panels.NOTE 3Adhesion may be influenced by the method of pretreating thebase metal and the type of steel used as a basis metal. Helpful informationis given in Practices B 177, B 183, B 242, and B 320.6.7 The coating shall be sufficiently free of pores to pass theporosity test specified (se
46、e 7.4).6.8 WorkmanshipAdding to (spotting in) or double elec-troplating, unless evidence of a satisfactory bond is established,shall be cause for rejection. Stripping and replating is permittedbut parts having an ultimate tensile strength greater than 1000MPa or a hardness greater than 32 HRC that a
47、re acid strippedshall be rebaked (see 6.3) before plating. Baking after strippingis not necessary if the parts are stripped anodically in analkaline solution.6.9 Supplemental RequirementsIf parts are electroplatedand subsequently ground to size, the grinding shall be donewith a proper coolant, never
48、 dry, and with a sufficiently lightcut to prevent cracking.4Macrocracking, visually observedwithout magnification after grinding, shall be cause for rejec-tion.6.10 PackagingPart(s) plated for the U.S. Governmentand Military, including subcontracts, shall be packaged inaccordance with Practice D 395
49、1.7. Test Methods7.1 Separate SpecimensWhen the coated articles are ofsuch a form as not to be readily adaptable to a test specifiedherein, when destructive tests would unreasonably reduce thenumber or pieces in small lots, when the pieces are toovaluable to be destroyed, and when specified by the purchaser,tests shall be made by the use of separate specimens platedconcurrently with the articles represented. The separate speci-mens shall be of a basis metal equivalent to that of the articlesrepresented. Equivalent basis metal includes chemical compo-sition, grade, con
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