1、. MIL-C-81751B 17 January 1972 Superseding 17 February 1971 MIL-C-81751A(AS) MILITARY SPECIFICATION COATING, METALLIC-CERAMIC This specification is mandatory for use by all Depart- ments and Agencies of the Department of Defense. 1. SCOPE 1.1 Scope - This specification covers the requirements of met
2、allic-ceramic coatings to provide corrosion and oxidation protection of metallic substrates. 1.2 Classification - Metallic-ceramic coatings shall be furn- ished in the following Types and Classes, as specified (see 6.2): Type I - Class 1 - Coating cured at 650.5 25F Class 2 - Coating cured at 650 +
3、25F and post treated at elevated temperature Class 3 - Initial coat(s) cured at 650 + 25“F, and burn- ished prior to applying top czat that is cured at 650 - + 25F Class 4 - Coating cured at 650 + 25F and post treated by burnishing - Type II - Class I - Coating fused at 1485 - + 35F L Class 2 - Coat
4、ing fused at 1485 + 35F and post treated by burnishing - Type III - Class 1 - Coating deposited by thermal spraying Class 2 - Coating deposited by thermal spraying and post treated by burnishing FSC MFFP 1 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-
5、,-,-MIL-C-81751B 2. APPLICABLE .DOCUMENTS * 2.1 The following documents of the issue in effect on date of invi!ation for bids or request for proposal, form a part of the speci- fication herein. SPECIFICATIONS Federal O-E-760 O-T-236 O-T-634 QQ-S-691 QQ-S-766 TT-C-490 TT- I- 7 35 Military MIL-S-5002
6、MIL-R-56 32 NIL-L-7808 MIL-E-22200/1 MIL-T-81533 Ethyl Alcohol (Ethanol) Denatured Alcohol, and Proprietary Solvent Tetrachloroethylene (Perchloroethylene), Tech- nical Grade Trichloroethylene, Technical Steel, Plate, Carbon, Marine Boiler Steel Plate, Sheet, and Strip - Corrosion Re- sisting Cleani
7、ng Methods and Pretreatment of Ferrous Surfaces for Organic Coatings Isopropyl Alcohol Surface Treatments and Metallic Coatings for Metal Surfaces of Weapons Systems Rods and Wire, Steel, Welding (For Aircraft Applications) Lubricating Oil, Aircraft Turbine Engine, Syrithetic Base Electrodes, Weldin
8、g, Mineral Covered, Iron Powder, Low Hydrogen Medium and High Tensile Steel, As Welded or Stress-relieved Weld Application Trichloroethane, 1, 1, 1, (Methyl Chloroform) Inhibited, Vapor Degreasing 2 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-fiI
9、L-C-BL75LB VF m 7777706 OLI20777 5 m - “ MIL-C-81751B STANDARDS Federal Fed. Test Method Paint, Varnish, Lacquer and Related Materials, Std. No. 141 Methods of Inspection, Sampling and Testing Fed, Test Method Metals, Test 1-kthods Std. No. 151 Military MIL-STD-205 Sampling Procedures and Tables for
10、 Inspection by Attributes (Copies of specifications, standards, drawings, and publications re- quired by suppliers in connection with specific procurement functions should be obtained fron the procuring activity or as directed by the con- tracting officer.) 2.2 Other publications - The following doc
11、uments form a parti of this specification to the extent specified herein. Unless otherwise indicated, the issue in effect on date of invitation for bids or request for proposa?. shall apply. American Society for Testing and Materials (ASTM) Standards B 117 Method of Salt Spray (Fog) Testing B 487 Me
12、thod for Measuring Metal and Oxide Coating Thickness by Microscopic Examination of a Cross Section B 499 Hethod for Measurement of Coating Thickness by the Magnetic Method: Nonmagnetic Coatings on Magnetic Basis Metal B 529 t Method for the Measurement of Coating Thickness by the Eddy Current Test M
13、ethod: Nonconductive Coatings on Nonmagnetic Basis Metals C 313 Method of Test for Adherence of Porcelain Enamel and Ceramic Coatings to Sheet Metal (Applications for copies of ASTM standards should be addressed to the American Society for Testing and Materials, 1916 Race Street, Phila- delphia, Pen
14、nsylvania 19103.) 3 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-C-81751B 3. REQUIREMENT S 3.1 First article samples - First article samples of the metallic-ceramic coatings shall be processed using the materials, methods and processes propose
15、d for production, The samples are for the purpose of determining that the processors .materials and processes will produce coatings on basis metals that will meet the requirements of this specifi- cation. These samples shall be inspected as specified in Section 4 and shall be submitted as directed b
16、y the procuring activity for examination and written approval. 3.2 Materials - The materials shall be such as to produce metallic-ceramic coatings which met the requirements of this specifica- tion, All ingredients used in the formulation shall be inorganic with the binder solids being either inorga
17、nic compounds, ceramic oxides or glass frits. 3.2.1 Ingredients - The ingredients for Type I coating shall be compounded to form an acidic aqueous slurry containing aluminumpowder and a homogeneous solution of binder solids. The ingredients for Type II coating shall be compounded to form an aqueous
18、slurry of metal or metal powders and ceramic binder solids. The ingredients for Type III coating shall be a dry blend of sprayable metal and ceramic powder. 3.2.2 Composition - The composition sf the materials shall be as formulated in Table 1 to form a metallic-ceramic coating when applied to the b
19、asis metal or to a metallic substrate, * TABLE I COMPOSITION - PERCENT BY WEIGHT Nonvolatile Contents Metal or Pigment Contents Binder Contents * 3.2.3 Pigment (Type I) - The pigment for Type I coating shall consist of commercially pure (99% minimum a1uminutn)spherical aluminum powder or atomized po
20、wder and shall contain no other filler or adulterant. The particle size distribution shall be as follows: Less than 15 microns - 90 percent by weight, minimum Less than 10 microns - 50 percent by weight, minimum 4 Provided by IHSNot for ResaleNo reproduction or networking permitted without license f
21、rom IHS-,-,-3.3 Equipment and processes - The equipment and processes employed to accomplish metallic-ceramic coatings shall be approved by the procuring activity. 3.3.1 Material and property control - Prior to production, controls shall be established to assure that the coatings conform to the requ
22、irements of this specification. talen processing practices-have been so established, the procedures shall not be changed without approval of the procuring activity. 3.3.2 Application processing - 3.3.2.1 Preparation - Surfaces to be coated shall be free from all contamination (see 3.4.3) prior to ro
23、ughening by dry grit blasting or wet vapor blasting with 100 to 250 mesh silica, silicon carbide, or alumina grit in accordance with Method I of TT-C-490 for Type I coatings. For Types II and III coatings, a dry 40 to 80 mesh grit shall be used for roughening heavy sections and others where applicab
24、le (see 6.6). The grit used for blasting shall be new. Residual grit shall be removed from parts by blasting with clean oil-free dry air. The surfaces after blast- ing shall conform to the surface roughness requirements specified in the contract, order or applicable drawing. 3.3.2.2 Application - 3.
25、3.2.2.1 Type I coating - The coating material shall be applied to the parts by spraying without any thinning of the material. After each spray application, parts shall be dried at 175 + 25F (80 + 14OC) for a minimum of 15 minutes. Unless otherwise specified or requyred by the metallurgical nature of
26、 the basis material, parts shall then be cured at 650 25F (343 5 14C) for a minimum of 15 minutes after the parts have reached the specified temperatures. When otherwise specified or required, parts shall be given a curing heat treatment at 375 + 25F (191 5 14C) for a minimum of 24 hours as a substi
27、tution for the curing at the more elevated temperature. Parts shall be at room temperature prior to apply- ing subsequent coats. 3.3.2.2.2 Type II coating - The coating material shall be applied parts shall be dried at 230 + 20F (110 + 11C) for a minimum of 15 min- utes to produce a dry or bisque co
28、ating. Parts shall then be fired in an air atmosphere furnace, either of the muffle or electric type, at 1485 + 35F (807 + 21C) for the length of time established by the supplier for the particlar coating formulation. .i r to the parts by spraying, dipping, slushing or draining. After application, -
29、 3.3.2.2.3 Type III coating - The coating material shall be applied to the parts by thermal spraying either by flame spraying techniques using oxygen together with acetylene or stabilized methylacetylene propadiene or plasma-arc flame spraying either by the vortex stabilized jet or gas 5 Provided by
30、 IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-C-81751B sheath stabilized jet torch. Application shall be in accordance with the process established by the supplie!: for the particular coating formu- lation. 3.3.3 Coating characteristics - 3.3.3.1 Type I,
31、class 1 - Type I, class 1 coatings shall be non- conductive and shall require no further treatment after final curing at 650 - + 25F. 3.3.3.2 Type I, class 2 - Type I, class 2 coatings shall be con- ductive. They shall be developed by heating the parts at elevated tem- perature after final curing at
32、 650 + 25F. After reaching the required temperature, the coated parts shou17 be held at this temperature for a sufficient time to develop specified properties. Temperature and times for post heat treatment are given in Table II, TABLE II TIMJ3 FOR POST HEAT TREATMENT FOR CLASS 2 COATINGS . Temperatu
33、re Range - F Heating Time - Minutes 1090 to 1110 10 990 to 1010 90 940 to 968 240 3.3.3.3 Type I, class 3 - Type I, class 3 coatings shall be non- conductive. These coatings shall be developed by burnishing the first coating prior to application and curing of the top coat. The coating shall-remain n
34、onconductive unless heated in service to elevated tempera- tures or burnished, thus changing the electrical properties. Parts shall be burnished by rolling, peening, light blasting, wire brushing, etc, Materials for burnishing should be chemically inert. They shall not leave a smudge deposit on the
35、coating, shall not cause damage to delicate parts, shall not abrade the coating or shall not introduce impurities into the coating. 3.3.3.4 Type I, class 4 - Type I, class 4 coatings shall be con- ductive. They shall be developed by burnishing the parts after final curing at 650 4- 25F. The parts sh
36、all be burnished as detailed in 3.3.3.3. The aesthetic qualities of the coating will also be increased without af- fecting the corrosion properties. The matte gray surface finish when burnished, will achieve either a satin luster or produce a bright polished mirror-like surface. 6 Provided by IHSNot
37、 for ResaleNo reproduction or networking permitted without license from IHS-,-,-3.3.3.5 Type II, class 1 - Type II, class 1 coatings shall be conductive and shall require no further treatment after fusing. The coating shall be applicable to basis metals capable of withstanding the 1485 + 35OF firing
38、 schedule without loss of the required physical and mechaKical properties as detailed in the applicable basis metal material specification. 3.3.3.6 Type II, class 2 - Type II, class 2 shall be developed by buffing, polishing or burnishing the Type II, class 1 coating by pro- cedures detailed in 3.3.
39、3.3. This operation is not required to attain the specified oxidation and corrosion resistance properties as only the aesthetic qualities of the coating are achieved to produce a metallic - lus ter. 3.3.3.7 Type III, class 1 - Type III, class 1 coatings shall be conductive and shall require no furth
40、er treatment after thermal spraying. The coating, as sprayed shall be essentially pore-free and ductile. The coating is applicable for basis metals where temperature of other types of coating applications can effect changes in required physical and me- chanical properties as detailed in the applicab
41、le basis metal specifica- tions as well as the effects of shot peening and other residual compres- sive stress inducing treatments. Generally, the temperature of the basis metal will not exceed 350F (177C) during application. 3.3.3.8 Type III, class 2 - Type III, class 2 coatings are de- veloped by
42、buffing, polishing, or burnishing, as detailed in 3.3.3.3, the Type III, class 1 coatings. This operation is not required to attain the specified oxidation and corrosion resistance properties as only the aesthetic qualities of the coating will be increased. 3.4 General requirements - 3.4.1 Basis met
43、al - The basis metal shall be free from visible defects which will be detrimental to the appearance or protective value of the coating. Unless otherwise specified, the coating shall be applied after all basis metal heat treatments and mechanical operations such as machining, brazing, welding, formin
44、g and perforating of the article have been completed. The basis metal shall be subjected to such cleaning and coating procedures as necessary to yield coatings as herein specified. * 3.4.2 Stress relief treatment - All steel parts shall be given a stress relief heat treatment at a minimum of 375 +.2
45、5F (191 -k 14C) for 3 hours or more prior to cleaning and coating i? they contaTn or are suspected of having residual tensile stresses caused by machining, grind- ing or cold forming operations. Parts which are cold straightened and cold formed are considered to contain damaging tensile stresses (se
46、e 6.4). The temperature and time at temperature shall be such that maximum stress relief is obtained without reduction in hardness to less than the specified mnimum. 7 Provided by IHSNot for ResaleNo reproduction or networking permitted without license from IHS-,-,-MIL-C-81751B 3.4.3 Cleaning - All
47、steel parts having a hardness Rockwell C33 and higher shall be cleaned using materials which will have no damag- ing effects on the metal, including freedom from pits, intergranular attack, etching and hydrogen embrittlement. Steel parts having a hardness of less than Rockwell C33 which have been ex
48、posed to hydrogen contamination processes such as cathodic cleaning, pickling, and etching shall be heat treated at a minimum of 375 f 25OF (191f 14C) for 3 hours or more prior to surface preparation and blasting. Other basis metals shall be cleaned in accordance with MIL-S-5002, Prior to coating, c
49、leaned steel parts shall be degreased in accordance with Method II of TT-C-490 with a suitable solvent such as trichloroethylene, O-T-634; perchloroethylene, O-T-236; or 1, 1, 1 trichloroethane, MIL-T-81533. Titanium alloys shall be cleaned in accord- ance with MIL-S-5002. To prevent stress corrosion cracking of titanium alloys, they shall not be degreased in chlorinated hydrocarbon solvents
