1、NOTE: MIL-STD-341 (AT) has been redesignated as a handbook, and is to be used for guidancepurposesonly.Thisdocument isno longertobe citedasarequirement.For administrativeexpediency,theonly physical change from -STD-341 (AT) iS tS coverPage. However tsdocument isno longertobe citedasarequirement.Ifci
2、tedasarequirement,contractorsmaydisregardtherequirementsofthisdocument and interpretitscontentsonlyasguidance.INCH-POUNDJMIL+IDBK-341(AT)27 Febrwuy 1998DEPARTMENT OF DEFENSEHANDBOOKCOATING, ALUMINUM AND SILICONDIFFUSION, PROCESS FORAMSC N/A FSC 8030DISTRIBUTION STATEMENT A. Approved forpublicrelease
3、;distributionisunlimited. Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-341 (AT)DEPARTKENT OF DEFENSEWashngton, DC 20301Coating, Aluminum and Silicon Diffusion, Process for1. This Military Standard is approved for use by U.S. ArmyTank-Autom
4、otive Colmmand, Department of the Army, and is available for use byall Departments and Agencies of the Department of Defense.2. Beneficial comments (recommendations, additions, deletions) and anypertinent data which may be of use in improving this document should beaddressed to: US Army Tank-Automot
5、ive Command, ATTN: AMSTA-GDS, Warren, Ml48397-5000, by using the self-addressed Standardization Document ImprovementProposal (DD Form 1426) appearing at the end of this document or by letter.iiProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-IMIL-STD-
6、341 (AT)FOREWORDThis military standard describes the diffusion process for aluminum andsilicon coating for high temperature parts used in gas turbine engines forground vehicles.IProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-HIL-STD-341(AT)CONTENTSP
7、aragraph 1.1.11.22.3.3.13.24.4.14.1.14.1.24.24.2.14.2.24.2.34.2.44.34.45*5.15.25.2.15.2.25.2.35.2.45.2.55.2.65.2.6.15.2.75.35.3.15.3.25.3.2.15.46.6.16.26.3SCOPEa71 *S*,.*.*.*a71 *.*,*.*.,.purpose .scope* a71 .*.,REFERENCED DOCUMENTS (Not applicable) DEFINITIONS .a71 *a71 a71 a71 .a71 *a71 a71 .Diffu
8、sion coating .Aluminize .GENEBAL REQUIREMENTS. Equipment .Drying oven .Diffusion furnace .Material .Vapor decreasing solvent Dryabraaive blast hart gaaea .C0ating8aterial a71ixing .Test specimens Process approvals .DETAILED REQUIREMENTS Diffusion coating material. of.Procedures and operations .Coati
9、ng material preparation Surface preparation .Diffusion coating material application Curing Inspection (prediffusion treatment) .Diffusion treatment .Racking .Post cleaning .Teat methods Visual Metallographic Coating thickness .Rework NOTES Intended useSubject term (key word) listing .Supersession da
10、ta .Page11123334444444444455555556666666667777Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-341(AT)10 SCOPE1.1 Purpose. This iB one of the coating processes used to provide acoating on certain metallic parts to protect them against oxidatio
11、n,sulfidation or erosion at high temperature operation, and resistance tothermal shock during cycling.1.2 Scope. This standard covers the procedure for applying aluminum andsilicon by the diffusion coating process.III)-1-I1IProvided by IHSNot for ResaleNo reproduction or networking permitted without
12、 license from IHS-,-,-MIL-STD-341(AT)2. REFERENCED DOCUMENTS(This section is not applicable to this standard.)2 -Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-341(AT)3. DEFINITIONS3.1 Diffusion coating. Any process whereby a basis metal or
13、alloy iseither: (1) coated with another metal or alloy and heated to a sufficienttemperature in a suitable environment or (2) exposed to gaseous or liquidmedium containing the other metal or alloy. The result is diffusion of thecoating or of the other metal or alloy into the base metal with resultan
14、tchange in the composition and properties of its surface.3.2 Alumlnide. Alumfnide is the protective surface alloy formed as aresult of aluminum diffusion into the base metal.-IProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I(IIIIII4.4.1llIL-sTD-341(
15、AT)GENERAL REQU1=NTSEquipmnlJ.4.1.1 Drying oven. The drying oven shall be a recirculating type ofoven with a71uitable controls to operate at 625 10 degrees Fahrenheit (F)3305 degrees Celsiuc (C).4.1.2 Diffusion furnace. The diffusion furnace shall be a controlledatmosphere furnace capable of a71aint
16、aining temperatures up to 1950 25F(1065 15C).4.2 Matarials.4.2.1 Vapor decreasing solvent. The vapor decreasing solvent shall bestabilized 1-1-1 trichloroethane or equivalent type solvent.4.2.2 Dry abrasive blast. The dry abrasive blast material shall be 220mesh aluminum oxide (A1203), zirconite 200
17、 or equivalent.4.2.3 Inert gasas. The diffueion shall be done in one of the followingat90epherea:a. bercially pure argon with a dew point of at least -40”F(-40”C).b. Comrcially pure hydrogen with a dew point of at least -40”F(-4(YC).4.2.4 Coating material mixin As the coating mixture solids willsett
18、le into a very compact mass on standing, it is very important that thecoating mixture in thoroughly mixed in its original container to ensure theliquid to solids ratio is maintained. To ensure thorough mixing of thecoating mixture, the original container can be placed on the rollers of aball mill an
19、d mechanically rolled until the coating mixture is in evensuspension.4.3 Tent specimens. Test specimens shall be prepared, coated anddiffusion treated with each lot of parts, and submitted to the procuringactivitys material laboratory for examination. There shell not be laes thanone tast specimen, p
20、rocessed through the coating and thermal processing, formicroscopic examination. Test specimens shall be made of the same alloy asthe parts being processad.4.4 Process approvals. As a condition of procurement and manufacturing,specific work inatructiona (process procedures) and changes or reviaona o
21、fsuch work instructions shall be submftted to the procuring activityaa71ater%al laboratory for approval.4Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-STD-341(AT)5. DETAILED REQUIREMENTS5.1 Diffusion coating material. The diffusion coating mate
22、rial shall beSermaloy “J” of Sermetel, a subsidiary of Teleflex Incorporated,International Headquarters, Limerick Road, Limerick, Pennsylvania 19468, orequivalent.5.2 Procedures and operations.5.2.1 Coating material preparation. The diffusion coating materialshall be thoroughly mixed prior to use as
23、 follows:a. Agitate or shake the coating material in its original containerfor at least 15 minutes.b. Strain coating material successively through 50, 100 and 150mesh screens to remove all agglomerated material.5.2.2 Surface preparation. The surface preparation of the parts orassemblies to be coated
24、 shall include the following:a. Parts or assemblies shall be vapor degreased.b. Areas of partB or assemblies not requiring coating shall besuitably masked.c. Arezs of ?arts cr assemblies t be ccwted shall be thoroughlydry abrasive blasted (see 4.2.2) using an air pressure of 60pounds per square inch
25、 (psi). When damaged coatings are befngreworked by this coating process the edges of the damagedcoated shall be suitable feathered.CAUTION : After abrasive blasting, parts or assemblies shall only behandled in a manner which will preclude recontamination.In as much as possible, touching the area to
26、be coatedshall be avoided.5.2.3 Diffusion coating material application. The diffusion coatingmaterial (see 5,2.1) shall be sprayed dipped, or brushed on the areas to becoated. The coating shall be applied by alternately applying a coating of 2or 3 roils 0.051 to 0.076 millimeter (mm) and then curing
27、 until a total coat.material thickness is reached which will provide the proper finished coatingthickness after the diffusion treatment.5.2.4 Curing. Curing shall be as follows:a. Bake coated parts at a temperature of 175 10”F (80 SC) for15 minutes.b. Remove masking.5Provided by IHSNot for ResaleNo
28、reproduction or networking permitted without license from IHS-,-,-IIic. Cure coated partsfor not less thanMIL-STD-341(AT)at a temperature of 625 25F (330 15”C)1 hour.CAUTION : Coating is very friable and shall not be handled.5.2.5 Inspection (prediffueion treatment). Visually inspect coating forcraz
29、ing, cracktng, and any other visible surface defects. Defective coatingsshall be stripped and recoated in accordance with 5.2.1 through 5.2.3.5.2.6 Diffusion treatment. Unless otherwise specified on theengineering drawing, cliffusion treatment shall be done in an argon orhydrogen atmosphere. The par
30、t temperature shall be raised to the temperatureapproved by the procurtng activitys material laboratory and held at heat forat least one hour. The parts shall be cooled to at least 400F (205”C) in acontrolled atmosphere then the part may be removed and cooled in air.5.2.6.1 Rackin4. Coated parts sha
31、ll be racked in such a manner topreclude the coating area from touching either the racks or retort.5.2.7 Post cleani he powder residue on the parts after diffusionheat treatment may be removeddiffusion coatings thicknessby any method which will not affect theor properties.5.3 Test methods.and assemb
32、lies and test specimens shall be5.3.1 Visual. All partsvisually inspected to verify the diffueion coating is adherent to the basematerial and ha8 a uniform continuous surface free from spalling, chipping,flaking, cracking and other objectionable imperfections.5.3.2 Metallographic. When examined at l
33、OOX magnification, aImicroscopic examination of the test specimen cut normal to the coated surfaceshall not reveal any cracka, porosity, pitting or other imperfections whichwould expose the base metal.5.3.2.1 Coating thickness. The coating thickness of the diffusedcoating shall be meaaured to verify
34、 a coating thickness of 2.0 to 3.0 roils1I (0.051 to 0.076 ) or to the thickmess specified on the engineeringdrawing.5.4 Rework. Damaged or imperfect coatings wy be reworked once withoutfurther approvals provided the coating is completely removed by mechanicalmthods .6 -Provided by IHSNot for Resale
35、No reproduction or networking permitted without license from IHS-,-,-MIL-STD-341(AT)6. NOTES-6.1 Intended use. The process covered by this standard is intendedprimarily for use as a diffusion coating which provides an oxidation,sulfidation, erosion and thermal shock resistant surface.6.2 Subject ter
36、m (key word) listinAluminum coating proceseDiffusion coating processProcess for diffusion coatingSilicon coating process6.3 Supersession data. This military standard supersedes AVCO Lycomingspecification number P6413, revision C, dated 26 April 1982.Custodian:Army - ATPreparing activity:Army - AT(Project 8030-A120)I-I17IIIProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-I1iIIIIIIIIIIIIIIIIII DO,%s.1426 PREVtOm EDITION IS OLETEProvided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-
