1、_ SAE Technical Standards Board Rules provide that: “This report is published by SAE to advance the state of technical and engineering sciences. The use of this report is entirely voluntary, and its applicability and suitability for any particular use, including any patent infringement arising there
2、from, is the sole responsibility of the user.” SAE reviews each technical report at least every five years at which time it may be reaffirmed, revised, or cancelled. SAE invites your written comments and suggestions. Copyright 2011 SAE International All rights reserved. No part of this publication m
3、ay be reproduced, 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 U
4、SA) Fax: 724-776-0790 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/AMS2452 AEROSPACE MATERIAL SPECIFICATION AMS2452 Issued 2011-06 Superfinishing of HVOF Applie
5、d Tungsten Carbide Coatings RATIONALE Superfinishing is a process that follows in the process sequence after grinding of tungsten carbide HVOF coatings that have been ground in accordance with AMS2449. The superfinishing process requires different equipment and procedures from grinding and therefore
6、 merits separate documentation. NOTICE ORDERING INFORMATION: The following information shall be provided to the superfinishing processor by the purchaser. 1) Purchase order shall specify not less than the following: AMS2452 Basis metal under tungsten carbide Type of HVOF tungsten carbide coating to
7、be superfinished. See AMS2447 or AMS2448. Coating thickness required after superfinishing Coating acceptance criteria if not as specified herein Minimum and maximum surface finish requirements. Examples: Ra (average roughness), Rz (average peak to valley height), Rp (mean line to highest peak height
8、), Tp/Mr/Rtp/Rmr (bearing ratio), or other relevant parameters may be specified as necessary to adequately characterize the required surface finish depending on the application. See 3.6 and 8.2.7. Finish diameter and/or dimensional requirements after processing. See 8.5. Quantity of parts to be supe
9、rfinished SAE AMS2452 Page 2 of 13 1. 1. SCOPE 1.1 Purpose This specification covers requirements for the superfinishing of High Velocity Oxygen/Fuel (HVOF) applied tungsten carbide thermal spray coatings. 1.1.1 Superfinishing is a process used to produce high quality surface finishes characterized
10、by low Ra (roughness average), such as 8 inch Ra or less, in comparison to conventional ground coatings as in AMS2449. See 8.2.6. 1.2 Application This process has been used typically to superfinish tungsten carbide HVOF coatings applied in accordance with AMS2447 or AMS2448 to high strength steels f
11、or applications requiring wear, heat, and corrosion resistance or dimensional restoration, such as aircraft landing gear and hydraulic actuator components. However, usage is not limited to such applications. Tungsten carbide HVOF coated surfaces for seal applications such as hydraulic actuators typi
12、cally require a surface roughness of 0 to 4 inch (0 to 0.1 m) Ra. Tungsten carbide HVOF-coated surfaces mating with a bushing or sleeve typically require a surface finish of 4 to 8 inch (0.1 to 0.2 m) Ra. This process follows grinding of HVOF coatings processed in accordance with AMS2449. The intent
13、 of this specification, in addition to improving surface finish, is to change the morphology or surface characteristics in order to prolong the service life of the component. 1.3 Safety - Hazardous Materials While the materials, methods, applications, and processes described or referenced in this sp
14、ecification may involve the use of hazardous 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 meas
15、ures to ensure the health and safety of 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 unl
16、ess a specific document issue is specified. When the referenced document has been cancelled and no superseding document has been specified, the last published issue of that document shall apply. 2.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001,
17、 Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. AMS2447 Coating, Thermal Spray, High Velocity Oxygen/Fuel Process AMS2448 Application of Tungsten Carbide Coatings on Ultra High Strength Steels, High Velocity Oxygen/Fuel Process AMS2449 Grinding of HVOF Sprayed
18、Tungsten Carbide Coatings Applied to High Strength Steels ARP5935 Use of HVOF Thermal Spray Coatings for Hard Chrome Replacement in Landing Gear Applications 2.2 ASME Publications Available from American Society of Mechanical Engineers, 22 Law Drive, P.O. Box 2900, Fairfield, NJ 07007-2900, Tel: 973
19、-882-1170, www.asme.org. ASME B46.1 Surface Texture (Surface Roughness, Waviness, and Lay) SAE AMS2452 Page 3 of 13 3. TECHNICAL REQUIREMENTS 3.1 Parts to be superfinished shall have been coated with tungsten carbide coating in accordance with AMS2447 or AMS2448 and ground to a surface roughness of
20、12 to 20 inch (0.3 to 0.5 m) Ra in accordance with AMS2449. 3.2 Surface Finish Unless otherwise specified by the cognizant engineering organization, the surface roughness after superfinishing shall be 4 inch (0.1 m) Ra or better. Surface finish shall meet the minimum and maximum values specified for
21、 Ra, Rp, Rz, and Tp/Mr/Rtp/Rmr or other parameters specified by the purchaser, including finish diameter and/or dimensional requirements after all processing has been completed. See 8.2.7 and 8.5. Type 1 surfaces in accordance with ARP5935 are surfaces that require sealing a hydraulic fluid with a s
22、liding interface, such as landing gear struts and hydraulic actuator piston rods. To maximize seal life for these applications, superfinishing to 4 inch (0.1 m) Ra or better is required. ARP5935 recommended surface finish parameters for Type 1 surfaces include Rz of 40 inch maximum (1.0 m), Rp of 8
23、inch maximum (0.2 m), Rmr 70 to 90% at Co=5% and C1=0.25Rz. See 3.6 and 8.2.7. 3.3 Cleaning Protective coatings and other foreign materials shall be removed from parts prior to superfinishing to preclude contamination of cutting fluid (coolant) and abrasives. 3.4 Superfinishing Process Requirements
24、Parts shall be processed in accordance with 3.4.1 or 3.4.2. The superfinishing process shall be performed in accordance with Tables 1, 2, or 3, as applicable, and Figures 1 or 2, a stone or tape Superfinishing Process Control Sheet (or equivalent acceptable to the cognizant engineering organization)
25、, as applicable, to result in acceptable parts. 3.4.1 Stone Method The superfinishing equipment shall be mounted as an attachment on a suitable support machine (such as a lathe) capable of providing rotation to the workpiece and traverse of the attachment. A self-dressing, superfinishing stone shall
26、 be inserted into the stone guide. The stone shall oscillate perpendicular to the direction of rotational velocity of the component being superfinished. Stone guides shall be attached to pneumatic pistons and shall provide constant contact force, rather than being set to a specified infeed or discre
27、te stock removal depth per pass. 3.4.1.1 Superfinishing Stones A diamond abrasive stone shall be used. See 8.6. 3.4.1.1.1 Each of the following parameters shall be met when selecting an abrasive stone. 3.4.1.1.1.1 Abrasive shall be metal-bonded diamond. 3.4.1.1.1.2 Grit or grain size shall be 9 to 3
28、0 m. 3.4.1.2 Cutting Fluids (Coolants) Used for Stone Superfinishing Honing oil or mineral oil shall be used as a flushing medium to rinse away the particles between the stone and workpiece. Honing oil or mineral oil shall be applied to the part and stone during operation. 3.4.1.3 Workpiece Surface
29、Speed Used for Stone Superfinishing Unless otherwise specified, the surface speed of the workpiece shall be 25 to 75 surface feet per minute (SFPM) (7.5 to 22 m/minute). Direction of rotation shall be “forward” or counter-clockwise so that applied fluid is carried directly underneath the stone. SAE
30、AMS2452 Page 4 of 13 3.4.1.4 Contact Pressure for Stone Superfinishing On typical applications with typical superfinishing units the contact pressure shall be 30 to 45 psi (2 to 3 bars). 3.4.1.5 Traverse Rates Unless otherwise specified, traverse rates shall be 0.062 to 0.125 inches per revolution (
31、IPR) (1.6 to 3.2 mm per revolution). If spiral or other undesired optical patterns are being generated due to the traverse rate, traverse rate shall be consequently decreased. 3.4.1.6 Oscillation Rates Unless otherwise specified, the oscillation rate shall be 900 to 2400 strokes per minute (15 to 40
32、 Hz). 3.4.1.7 Processing with Diamond Polishing Paste After processing with the diamond stone is complete and the workpiece surface roughness has been brought down to the specified surface roughness, a diamond paste shall be used as required to remove spiral or other undesirable optical patterns usi
33、ng a hardwood/felt pad block. The part shall be cleaned to remove honing oil using a suitable method such as with acetone or alcohol in preparation for the diamond paste. The felt pad shall be saturated with mineral oil (or equivalent acceptable to the cognizant engineering organization) and a thin
34、strip of diamond paste applied to the pad. The diamond paste shall be evenly spread over the surface of the felt pad. 3.4.1.7.1 Polishing Paste Abrasive Requirements 3.4.1.7.1.1 Abrasive shall be diamond. 3.4.1.7.1.2 Grit or grain size shall be 3 m or 6 m. 3.4.1.8 Surface Speed When Using Diamond Po
35、lishing Paste The surface speed of the workpiece shall be 75 to 150 surface feet per minute (SFPM) (23 to 46 m per minute). Direction of rotation shall be “forward” or counter-clockwise so that applied fluid is carried directly underneath the stone. 3.4.1.9 Contact Pressure Contact pressure for poli
36、shing using diamond paste shall be 45 to 60 psi (3 to 4 bars). 3.4.1.10 Stone Superfinishing Method Surface finish requirements versus grit size selection for stone superfinishing shall be as specified in Table 1. Incoming surface quality will affect the results. Alternative grit sizes may be used w
37、hen approved by the cognizant engineering organization. SAE AMS2452 Page 5 of 13 TABLE 1 - SURFACE FINISH VS. GRIT SIZE 3.4.2 Abrasive Film/Tape Method The equipment shall be mounted as an attachment on a suitable support machine to provide rotation to the workpiece and traverse of the attachment. S
38、ee 8.9. 3.4.2.1 Superfinishing (Microfinishing and Lapping) Film Diamond abrasive film shall be used. Abrasive film shall be labeled with the complete film specification including abrasive type and grit size. See 8.7. 3.4.2.1.1 Each of the following parameters shall be met when selecting an abrasive
39、 film: 3.4.2.1.1.1 Abrasive shall be diamond. 3.4.2.1.1.2 Type shall be microfinishing film or lapping film. See 8.7 3.4.2.1.1.3 Grit or grain size shall be 3 to 125 m. 3.4.2.2 Cutting Fluids (Coolants) Used for Film Superfinishing A suitable cutting fluid shall be used which does not have an advers
40、e effect on the part being superfinished. Recirculating cutting fluids shall be continuously filtered to minimize recycling residue and swarf. The cutting fluid when using superfinishing film shall either be oil or water-soluble coolant. 3.4.2.3 Surface Speed When Using Superfinishing Film The surfa
41、ce speed of the workpiece shall be 100 to 400 surface feet per minute (SFPM) (30 to 122 m per minute). Slower surface speed will require longer finishing times to achieve desired finishes. Direction shall be counter to film index direction. 3.4.2.4 Film Index Rates When Using Superfinishing Film The
42、 film index rate shall be 0.75 to 1.5 inches per minute (IPM) (19 to 38 mm per minute). Faster film index rates will provide coarser finishes than slower film index rates. 3.4.2.5 Contact Pressure for Film Superfinishing The contact pressure shall be 15 to 60 psi (1 to 4 bars) unless otherwise state
43、d in equipment manufacturers operator manual or specification. Surface Roughn ess, Ra inch (m) Bearing Ratio, (%) Rz, (average peak to valley height), inch (m) Stone / Paste Grit Size, m12 - 20 (0.3 - 0.5) 50 - 65 60 - 160 (1.5 - 4) After Grinding5 - 10 (0.13 - 0.25) 65 - 85 25 - 80 (0.64 - 2) 30 m
44、(stone)2 - 4 (0.05 - 0.1) 70 - 90 10 - 32 (0.25 - 0.8) 15 m (stone)1.5 - 3 (0.04 - 0.08) 70 - 90 8 - 24 ( 0.2 - 0.6) 9 m (stone)1 - 2 (0.03 - 0.05) 70 - 95 5 - 16 (0.13 - 0.4) 6 m (paste)0.5 - 1.5 (0.01 - 0.04) 70 - 98 3 - 12 (0.08 - 0.3) 3 m (paste)SAE AMS2452 Page 6 of 13 3.4.2.6 Traverse Rates Tr
45、averse rates shall be 0.01 to 0.1 inch per revolution (IPR) (0.3 to 2.5 mm per revolution) for 2 inch (50 mm) wide film and 0.02 to 0.2 inch per revolution (IPR) (0.5 to 5 mm per revolution) for 4 inch (102 mm) wide film. Faster traverse rates will require more finishing passes per grade to achieve
46、desired finish although total finishing time should remain similar. If spiral or other undesired optical patterns are being generated due to the traverse rate, traverse rate shall be consequently decreased. 3.4.2.7 Oscillation Frequency The oscillation frequency for tungsten carbide coatings shall b
47、e 500 to 800 oscillations/minute (8.3 to 13 Hz). To achieve a wide cross-hatch pattern, oscillation frequency may be reduced to 100 oscillations/minute. Alternative frequencies may be used when approved by the cognizant engineering organization. 3.4.2.8 Lapping Film Superfinishing Method Surface fin
48、ish requirements versus grit size for tape superfinishing method using diamond lapping film shall be as specified in Table 2. Alternative grit sizes may be used when approved by the cognizant engineering organization. Incoming surface quality will affect these results. See 8.8. TABLE 2 - SURFACE FIN
49、ISH VS. LAPPING FILM GRIT SIZE 3.4.2.9 Microfinishing Film Superfinishing Method Surface finish requirements versus grit size for tape superfinishing method using microfinishing film shall be as specified in Table 3. Alternative grit sizes may be used when approved by the cognizant engineering organization. Incoming surface quality will affect the results. See 8.8. TABLE 3 - SURFACE FINISH VS.
