1、_ 6$(7HFKQLFDO6WDQGDUGV%RDUG5XOHVSURYLGHWKDW7KLVUHSRUWLVSX EOLVKHGE6$(WRDGYDQFHWKHVWDWHRIWHFKQLFDODQGHQJL neering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising therefrom, LVWKHVROHUHVSRQ
2、VLELOLWRIWKHXVHU SAE reviews each technical report at least every five years at which time it may be revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2016 SAE International All rights reserved. No part of this publication may be reproduced,
3、stored in a retrieval system or transmitted, in any form or by any means, electronic, mechanical, photocopying, recording, or otherwise, without the prior written permission of SAE. TO PLACE A DOCUMENT ORDER: Tel: 877-606-7323 (inside USA and Canada) Tel: +1 724-776-4970 (outside USA) Fax: 724-776-0
4、790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org SAE values your input. To provide feedback on this Technical Report, please visit http:/www.sae.org/technical/standards/AMS2448B AEROSPACE MATERIAL SPECIFICATION AMS2448 REV. B Issued 2004-10 Revised 2016-02 Superseding AMS2448A Ap
5、plication of Tungsten Carbide Coatings on Ultra High Strength Steels High Velocity Oxygen / Fuel Process RATIONALE AMS2448B was updated to clarify Resampling and Retesting requirements, correct nomenclature used for chemical strippers and to update microstructure inspection methods. 1. SCOPE 1.1 Pur
6、pose This specification covers engineering requirements for applying tungsten carbide thermal spray coatings to ultra high strength steels (220 ksi and above) utilizing high velocity oxygen fuel (HVOF) combustion driven processes and the properties for such coatings. The processes and procedures her
7、ein apply only to the properties of the as-deposited coating. 1.2 Application This process has been used typically to provide coatings that possess lower porosity and higher adhesive and/or cohesive strength than generally attainable with plasma spray and for applications requiring wear, heat, and c
8、orrosion resistance or dimensional restoration that were traditionally chrome plated. However, usage is not limited to such applications. 1.3 Safety - Hazardous Materials While the materials, methods, applications, and processes described or referenced in this specification may involve the use of ha
9、zardous materials, this specification does not address the hazards which may be involved in such use. It is the sole responsibility of the user to ensure familiarity with the safe and proper use of any hazardous materials and to take necessary precautionary measures to ensure the health and safety o
10、f all personnel involved. 2. APPLICABLE DOCUMENTS The issue of the following documents in effect on the date of the purchase order forms a part of this specification to the extent specified herein. The supplier may work to a subsequent revision of a document unless a specific document issue is speci
11、fied. When the referenced document has been cancelled and no superseding document has been specified, the last published issue of that document shall apply. SAE INTERNATIONAL $06% Page 2 of 12 2.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, T
12、el: 877-606-7323 (inside USA and Canada) or +1 724-776-4970 (outside USA), www.sae.org. AMS6345 Steel, Sheet, Strip, and Plate 0.95Cr - 0.20Mo (0.28 - 0.33C) (SAE 4130) Normalized or Otherwise Heat Treated AMS6356 Steel, Sheet, Strip, and Plate, 0.95Cr - 0.20Mo - (0.30 - 0.35C) (4132) AMS6454 Sheet
13、Steel, Strip, and Plate, 1.8Ni - 0.80Cr - 0.25Mo (0.38 - 0.43C) (SAE 4340), Consumable Electrode Melted AMS7881 Tungsten Carbide-Cobalt Powder, Agglomerated and Sintered AMS7882 Tungsten Carbide-Cobalt Chrome Powder, Agglomerated and Sintered SAE J442 Test Strip, Holder, and Gage for Shot Peening 2.
14、2 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959, Tel: 610-832-9585, www.astm.org. ASTM C633 Adhesion or Cohesive Strength of Flame Sprayed Coatings ASTM E384 Knoop and Vickers Hardness of Materials ASTM E1245 Determining t
15、he Inclusion or Second-Phase Constituent Content of Metals by Automatic Image Analysis ASTM E1920 Metallographic Preparation of Thermal Sprayed Coatings 2.3 U.S. Government Publications Copies of these documents are available online at http:/quicksearch.dla.mil. MIL-STD-871 Electro-Chemical Strippin
16、g of Inorganic Finishes 3. TECHNICAL REQUIREMENTS 3.1 Equipment 3.1.1 Torch A specially constructed gun that utilizes combustion products to generate a high velocity gas stream for heating of the coating material to a molten or plasticized state, and transfer of the coating material to the work piec
17、e shall be used. The torch shall be microprocessor-controlled and fitted with an automated device for regulating the gas(es) and fuel(s). The torch shall be mounted on an automated manipulating device during the deposition process to maintain a constant working distance and traverse rate or maintain
18、ed in a fixed position with the component mounted on a manipulating device that will maintain a constant working distance. 3.1.2 Gauges 3.1.2.1 Pressure gauges shall have a minimum accuracy of 1.5% of full scale. 3.1.2.2 Flow meters shall have a minimum accuracy of 2% of full scale. SAE INTERNATIONA
19、L $06% Page 3 of 12 3.1.3 Powder Feeder The powder feed system shall supply a metered flow of material. 3.2 Materials 3.2.1 Gases and fuels specifications used by the processor for procurement shall be acceptable to the cognizant engineering organization. 3.2.2 Coating material shall conform to AMS7
20、881 or AMS7882 unless otherwise specified by the cognizant engineering organization. All powders shall be dry, free flowing and uniformly blended. 3.3 Preparation 3.3.1 Cleaning Surfaces to be coated shall be thoroughly cleaned to remove oil, grease, dirt, paint and other foreign material. Final cle
21、aning shall take place no more than four hours prior to coating. Cleaning procedures shall not embrittle, pit, or damage surfaces to be coated. 3.3.2 Masking Parts shall be masked by any appropriate means to protect all surfaces that are not being coated. 3.3.3 Surface Conditioning After cleaning, s
22、urfaces to be coated shall be grit-blasted with aluminum oxide blast media at 60 to 80 psi (414 to 552 KPa) and 6 to 8 inches (152 to 203 mm) standoff distance to clean and prepare the surface for HVOF deposition. Grit shall be free from moisture, oil, dirt and other contaminants. Grit size shall be
23、 of the finest possible size necessary to achieve a 120 to 150 Ra surface roughness, but shall never be coarser than 54 grit. A surface profilometer shall be used to verify the proper surface conditioning for each procedure used. 3.4 Application 3.4.1 Process The parameters for gas flows and pressur
24、es, powder feed rates, and spray distance, as well as deposition rates and traverse speeds shall be determined by a statistical method designed to achieve the desired coating properties specified by this document and/or the cognizant engineering organization. 3.4.2 Preheating Surfaces to be coated s
25、hall be heated to remove moisture, Surface temperature shall not exceed 300 F (149 C). Preheating may be accomplished with the torch or by other suitable means and shall be monitored as specified in 3.4.3.4. 3.4.3 Coating The coating material shall be deposited on the designated surface in sufficien
26、t thickness to permit finishing to specified dimensions. 3.4.3.1 Areas on which coating is optional must be prepared and handled in the same manner as the area on which coating is required and adhesion requirements still apply. 3.4.3.2 A spray angle of 90 degrees 5 degrees should be maintained. For
27、cylindrical components, angle is measured relative to the centerline axis of the cylinder. For any application that requires a spray angle at less than 85 degrees, all test specimens shall be sprayed at the same angle as the component and all minimum mechanical property requirements will apply. SAE
28、INTERNATIONAL $06% Page 4 of 12 3.4.3.3 Spray deposition shall be continuous except for interruptions to measure coating thickness and/or for cooling cycles to maintain part below maximum allowable temperature. 3.4.3.4 Substrate Temperature Unless otherwise specified, maximum temperature of the subs
29、trate during preheating and coating application shall be controlled to not exceed 300 F (149 C). Temperature measurements shall be made utilizing a laser-sighted infrared (IR) thermometer with adjustable emissivity (0.1 to 0.99) and response time of less than 1 second. Measurement location shall be
30、taken on the parent metal adjacent to the edge of the coating as it traverses the area to be coated. If geometric or part size constraints do not allow this procedure to be followed, then the temperature shall be measured immediately adjacent to the coated area along the same path of travel as the g
31、un plume. Emissivity shall be set to a value for the coating being applied or the substrate being measured. Resolution of the IR thermometer shall be 1 C or 1 F, depending on the scale used and spot diameter should be less than 2.5 inch (64 mm) or equivalent to the actual diameter of the IR beam. 3.
32、4.4 Test Specimens Specimens required under 3.7 shall be coated, as far as practicable, using the process procedures identified on the Coating Process Control Sheet (see Figure 1) with the parts that they represent. Specimens representing components rotated under the spray shall be sprayed at the sa
33、me rotational speed and incremental step rate as the component. If there are multiple application angles on the same component, each of the deposition angles shall be evaluated with specimens for compliance with minimum mechanical property limits. Specimens shall be evaluated prior to coating applic
34、ation on production components. 3.4.5 Specimen Material Bond strength and metallographic specimens shall be fabricated from the same alloy and heat treat of the alloy being coated. Bend test specimens shall be fabricated from AMS6454, AMS6356 or AMS6345 and heat treated to produce a hardness of 40 H
35、RC minimum. 3.5 Surface Finishing 3URFHGXUHVIRUILQLVKLQJVKDOOEHLQDFFRUGDQFHZLWKWKHFRJQLDQWHQJLQHHULQJRUJDQLDWLRQ VVSHFLILFations. 3.6 Properties 3.6.1 Adhesion 3.6.1.1 Bend Test Specimens prepared and tested in accordance with 3.7.1 shall not show separation of the coating from the substrate, when e
36、xamined visually without magnification. Cracking of the coating and minimal separation at the specimen edges shall be considered acceptable. 3.6.1.2 Bond Strength Specimens, prepared and tested in accordance with 3.7.2, shall be 10 ksi (69 MPa) minimum. 3.6.2 Coating Hardness The coating hardness, t
37、ested in accordance with 3.7.3, shall be HV300g 950 minimum. SAE INTERNATIONAL $06% Page 5 of 12 3.6.3 Microstructure Metallographic preparation shall be performed in accordance with ASTM E1920. Examination of a suitably prepared cross-sectioned specimen shall show the coatings to be free from crack
38、s and delaminations. Repolishing can only be performed on specimens that show flaws induced by the polishing method. Oxide content cannot be induced and is not grounds for repolishing. Microstructural properties shall be evaluated in accordance with the following: 3.6.3.1 Voids and oxides shall be u
39、niformly distributed and not greater than 1% in any field of view when examined at 380 420X magnification on the cross sectioned specimen performed in accordance with ASTM E1245. Any single void greater than 0.002 inch (0.05 mm) shall be cause for rejection. Alternatively, if image analysis using a
40、threshold method is not available, then voids and oxides shall be uniformly distributed and not greater than 1% of any 0.020 inch length in any field of view when viewed at between 380 420X magnification on the cross sectioned specimen. Any single void greater than 0.002 inch (0.05 mm) shall be caus
41、e for rejection. 3.6.3.2 Unmelted Particles None in any field view at 180 - 220X magnification on the cross sectioned specimen performed in accordance with ASTM E1245. Alternatively, if image analysis using a threshold method is not available, then no unmelted particles are allowed in any 0.04 inch
42、length in any field of view when viewed at 180 220X magnification on the cross sectioned specimen. 3.6.3.3 Interface Contamination of the coating at the substrate interface with surface preparation media shall not exceed 10% in any field of view at 180 - 220X magnification performed in accordance wi
43、th ASTM E1245. Alternatively, if image analysis using a threshold method is not available, then contamination of the coating at the substrate interface with surface preparation media shall not exceed 10% of any 0.04 inch length in any field of view when viewed at 180 220X magnification on the cross-
44、sectioned specimen. Any coating separation at the interface will not be acceptable. Separation is defined as gap between the coating and substrate greater than 0.002 inch (0.05 mm) in length following directly along the bond line. Any length less than this will be considered acceptable voids or poro
45、sity. 3.6.3.4 Carbide Distribution In any 400X field of view, all carbides shall be uniformly distributed with no banding or clustering. 3.6.4 Residual Stress dimensions and properties in SI units and the Celsius temperatures are shown as the approximate equivalents of the primary units and are pres
46、ented only for information. 8.7 Purchase documents should specify not less than the following: AMS2448B Coating material if different from 3.2.2 Coating thickness required if not 0.003 inch minimum (see 3.6.6) Maximum temperature of substrate if not 350 F (177 C) (see 3.4.2) Masking boundary toleran
47、ces if different from 3.9 Frequency of test if not selected by processor (see 4.2.2 and 4.3.2) Coating acceptance criteria if not specified herein Quantity of parts to be coated. PREPARED BY AMS COMMITTEE % SAE INTERNATIONAL $06% Page 12 of 12 Figure 1 - Coating process control sheet PREPARED BY AMS COMM,77(%
