1、Designation: B650 95 (Reapproved 2018)Standard Specification forElectrodeposited Engineering Chromium Coatings onFerrous Substrates1This standard is issued under the fixed designation B650; the number immediately following the designation indicates the year oforiginal adoption or, in the case of rev
2、ision, 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 U.S. Department of Defense.1. Scope1.1 This specific
3、ation 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 thand
4、ecorative 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 re
5、sistance, 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, health, and environmental practices and deter-mine t
6、he applicability of regulatory limitations prior to use.1.4 This international standard was developed in accor-dance with internationally recognized principles on standard-ization established in the Decision on Principles for theDevelopment of International Standards, Guides and Recom-mendations iss
7、ued by the World Trade Organization TechnicalBarriers to Trade (TBT) Committee.2. Referenced Documents2.1 ASTM Standards:2B117 Practice for Operating Salt Spray (Fog) ApparatusB177 Guide for Engineering Chromium ElectroplatingB183 Practice for Preparation of Low-Carbon Steel forElectroplatingB242 Gu
8、ide for Preparation of High-Carbon Steel for Elec-troplatingB320 Practice for Preparation of Iron Castings for Electro-platingB374 Terminology Relating to ElectroplatingB487 Test Method for Measurement of Metal and OxideCoating Thickness by Microscopical Examination ofCross SectionB499 Test Method f
9、or Measurement of Coating Thicknessesby the Magnetic Method: Nonmagnetic Coatings onMagnetic Basis MetalsB504 Test Method for Measurement of Thickness of Metal-lic Coatings by the Coulometric MethodB507 Practice for Design of Articles to Be Electroplated onRacksB568 Test Method for Measurement of Co
10、ating Thicknessby X-Ray SpectrometryB571 Practice for Qualitative Adhesion Testing of MetallicCoatingsB602 Test Method for Attribute Sampling of Metallic andInorganic CoatingsB697 Guide for Selection of Sampling Plans for Inspectionof Electrodeposited Metallic and Inorganic CoatingsB762 Test Method
11、of Variables Sampling of Metallic andInorganic Coatings1This specification is under the jurisdiction of ASTM Committee B08 onMetallic and Inorganic Coatings and is the direct responsibility of SubcommitteeB08.03 on Engineering Coatings.Current edition approved June 1, 2018. Published December 2013.
12、Originallyapproved in 1978. Last previous edition approved in 2013 as B650 95(2013). DOI:10.1520/B0650-95R18.2For 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 sta
13、ndards Document Summary page onthe ASTM website.Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United StatesThis international standard was developed in accordance with internationally recognized principles on standardization established in the De
14、cision on Principles for theDevelopment of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.1B849 Specification for Pre-Treatments of Iron or Steel forReducing Risk of Hydrogen EmbrittlementB850 Guide for Post-Coat
15、ing Treatments of Steel for Reduc-ing the Risk of Hydrogen EmbrittlementD3951 Practice for Commercial PackagingE8 Test Methods for Tension Testing of Metallic MaterialsF1459 Test Method for Determination of the Susceptibilityof Metallic Materials to Hydrogen Gas Embrittlement(HGE)2.2 Other Standard:
16、MIL-S-13165 Shot Peening of Metal Parts33. Terminology3.1 Definitions:3.1.1 significant surfacesall surfaces upon which a de-posit of controlled thickness is required.3.1.1.1 DiscussionWhen a controlled deposit is requiredin holes, corners, recesses, and similar areas, special racking,auxiliary anod
17、es 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 B374.4. Classification4.1 Electrodeposited chromium coatings in accordance withthis specificati
18、on 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 forsalvage or as required for severewear resistance4.2 Unless otherwise speci
19、fied 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 obtained under normal electroplating conditions, thethickness of the deposit
20、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, ASTM designation, and issue date of thisspecification,5.1.2 Alloy and
21、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 significant surfaces if different from the 20-mmball rule (see 3.1.1),5.1
22、.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 B602 (see Section 8),5.1.10 The number of test specimens for destructive testing(see 7.1),5.1.11 Thickn
23、ess, 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 subsequently ground to size,5.1.14 Where required, the base metal finish in terms
24、 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 the electroplating facility with test specimens (seeSection 7) to be electr
25、oplated 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 The appearance of the chromium coating on the signifi-cant surfaces of the pr
26、oduct shall be smooth and free of visualdefects such as blisters, pits, roughness, cracks, burneddeposits, uncoated areas, or macrocracking of the deposit thatis visible without magnification. The boundaries of electroplat-ing that cover only a portion of the surface shall, after finishingas indicat
27、ed 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 (scratches,pores, roll marks, inclusions, etc.) and that persist in the fin
28、ishdespite 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 metal,inclusions, pores, and other defects. It is recommended that the speci
29、fi-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, andelectropolishing, which are not normal in the treatment steps preceding theapplicati
30、on 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 should be shot peened (see MIL-S-13165C) or given an alternate mechanical tr
31、eatment 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 32 HRC) or greater,that may contain residual stress caused by various fabricat
32、ionoperations such as machining, grinding, straightening, or coldforming, will require one of the stress relief heat treatments3Available from Standardization Documents Order Desk, Bldg. 4 Section D, 700Robbins Ave., Philadelphia, PA 19111-5094, Attn: NPODS.B650 95 (2018)2prescribed in Specification
33、 B849 prior to electroplating. In allcases, the duration of heat treatment 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-
34、0 treatment is provided for parts that the purchaserwishes to exempt 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 s
35、afe performance of chromium plated itemsfabricated from those steels. 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 embri
36、ttlement failure of the part. The relative suscep-tibility of a steel can be determined by subjecting it to the DiskRupture Test of Test Method F1459. 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 suf
37、feran unacceptable reduction in hardness by treatment in accor-dance with Specification B849 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 purchase
38、r mayrequire that the heat-treatment temperature shall 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 co
39、mpressivestresses, the temperature shall not exceed 230C.6.4 Hydrogen Embrittlement Relief:6.4.1 Heat treatment appropriate for the tensile strength ofthe electroplated part (see Specification B850) shall be per-formed to reduce the risk of hydrogen embrittlement. In allcases, the duration of the he
40、at treatment shall commence fromthe time at which 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 Be
41、gin the embrittlement relief heat-treatment as soonas 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 c
42、onform to the requirements ofthe specified class 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 (see
43、4.1). Variation in the coating thickness from point 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 thespecif
44、ied value at all points. Hence, in most cases, the average coatingthickness on an article will be greater than the specified value; how muchgreater is largely determined by the shape of the article (see PracticeB507) and the characteristics of the electroplating process. In addition, theaverage coat
45、ing thickness on articles will vary from article 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
46、a single article meets the requirement. This may 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
47、 and therefore, in most cases, should beperformed 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 B177, B183, B242, and B320.6.7 The coating shall be sufficiently free of
48、pores to pass theporosity test specified (see 7.4).6.8 WorkmanshipAdding to (spotting in) or doubleelectroplating, unless evidence of a satisfactory bond isestablished, shall be cause for rejection. Stripping and replatingis permitted but parts having an ultimate tensile strengthgreater than 1000 MP
49、a or a hardness greater than 32 HRC thatare acid stripped shall be rebaked (see 6.3) before plating.Baking after stripping is not necessary if the parts are strippedanodically in an alkaline solution.6.9 Supplemental RequirementsIf parts are electroplatedand subsequently ground to size, the grinding shall be donewith a proper coolant, never 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, includi
