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 revised, reaffirmed, stabilized, or cancelled. SAE invites your written comments and suggestions. Copyright 2014 SAE International All rights reserved. No part of this p
3、ublication may 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: +1 724-776-497
4、0 (outside USA) 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/AMS2759/10A AEROSPACE MATERIAL SPECIFICATION AMS2759/10 REV. A Issued 1999-05 Rev
5、ised 2006-06 Reaffirmed 2014-04 Superseding AMS2759/10 Automated Gaseous Nitriding Controlled by Nitriding Potential RATIONALE AMS2759/10A has been reaffirmed to comply with the SAE five-year review policy. 1. SCOPE 1.1 Purpose This specification establishes requirements and procedures for generatin
6、g nitrided surfaces on steel parts using a process controlled by the nitriding potential. See definition of compound layer in 8.5.1. 1.2 Application The nitriding process described herein is used typically to produce a nitride case on carbon and alloy steels, tool steels, nitriding steels, corrosion
7、 resistant steels and other ferrous alloys. Applicable, allowance should be made for growth (See 8.4). 1.2.1 Specifically, the nitriding process described herein is recommended for those nitriding applications where engineering drawings do not permit a white layer or only a limited white layer thick
8、ness. 1.3 Classification The nitriding processes described herein, are classified as follows: 1.3.1 Class 0 No white layer permitted. (Not recommended for stainless steels.) 1.3.2 Class 1 0.0005 inch (0.013 mm) maximum white layer thickness permitted. 1.3.3 Class 2 0.001 inch (0.025 mm) maximum whit
9、e layer thickness permitted. 1.3.4 If no class is specified, Class 2 applies. Class 2 is not recommended for corrosion resistant steels. SAE INTERNATIONAL AMS2759/10A Page 2 of 9 2. APPLICABLE DOCUMENTS The issue of the following documents in effect on the date of the purchase order forms a part of
10、this specification to the extent specified herein. The supplier may work to a subsequent revision of a document unless 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 sha
11、ll apply. 2.1 SAE Publications Available from SAE International, 400 Commonwealth Drive, Warrendale, PA 15096-0001, Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), or www.sae.org. AMS 2418 Plating Copper AMS 2750 Pyrometry AMS 2759 Heat Treatment of Steel Parts, General Requ
12、irements AMS 2429 Bronze Plate Masking ARP1820 Chord Method of Evaluating Surface Characteristics 2.2 ASTM Publications Available from ASTM International, 100 Barr Harbor Drive, P.O. Box C700, West Conshohocken, PA 19428-2959 Tel: 610-832-9585, or www.astm.org. ASTM A 370 Standard Test Methods and D
13、efinitions for Mechanical Testing of Steel Products ASTM E 92 Vickers Hardness of Metallic Materials ASTM E 140 Hardness Conversion Tables for Metals ASTM E 384 Microhardness of Materials 3. TECHNICAL REQUIREMENTS 3.1 Equipment 3.1.1 Heating Equipment Shall conform to the requirements of AMS 2759. 3
14、.1.2 Gases Gases used for the nitriding process (anhydrous ammonia and nitrogen) shall be of the high purity grade (99.98%) with dew point -54 F (-48 C) or lower. 3.1.3 Controls 3.1.3.1 Pressure Controls The control equipment shall maintain pressure above atmospheric in the furnace retort throughout
15、 the process. 3.1.3.2 Nitriding Atmosphere The composition of the ingoing gas mixture and the nitriding potential for each stage of the process shall be automatically controlled, maintained and recorded (See 8.5.3). 3.1.3.3 Atmosphere Flow Rate Controls Devices for accurate control of flow rates of
16、the individual gases shall operate automatically in response to signals from the atmosphere analyzer. SAE INTERNATIONAL AMS2759/10A Page 3 of 9 3.1.3.4 Shut-Downs and Alarms The system shall be capable of automatically and safely shutting down the process in the event of any malfunction of the equip
17、ment such as power failure, interruption of gas flow, or any parameters exceeding their tolerance limits before damage occurs to the parts being processed. 3.2 Heat Treatment Prior to Nitriding 3.2.1 Heat Treatment Condition Steels hardenable by heat treatment shall be in the quenched and tempered,
18、or solution treated and aged condition. Unless otherwise specified, heat treatment procedure shall conform to AMS 2759. For materials not covered by AMS 2759, heat treatment parameters shall be as specified by the cognizant engineering organization and process controls shall be in accordance with AM
19、S 2759. The highest nitriding temperature shall be at least 50 F (30 C) below the lowest tempering or aging temperature. 3.2.2 Surface Condition Surfaces to be nitrided shall be free from decarburization, as determined in accordance with ARP1820 or equivalent microhardness techniques. Decarburized z
20、one is defined as the material having a hardness 20HK points or more softer than that of the core. 3.3 Pyrometry In accordance with AMS 2750. 3.3.1 Load Thermocouples If used, shall be sheathed and sealed. 3.4 Preparation for Nitriding 3.4.1 Unless otherwise specified, parts which have been ground,
21、straightened or otherwise mechanically worked after heat treatment shall be stress relieved prior to nitriding. The stress-relief temperature shall be in accordance with AMS 2759. 3.4.2 Part surfaces to be nitrided shall be free from grease, oil, oxidation, and other contaminants. 3.4.3 Part surface
22、s which are not to be nitrided shall be masked by a suitable maskant, e.g., copper (AMS 2418), bronze (AMS 2429), or by alternative methods like nickel, or other copper or bronze plating, pastes or paints, acceptable to the cognizant engineering organization. Copper plate shall be fine-grained and n
23、on-porous, not less than 0.001 inch (0.025 mm) in thickness. If bronze plating is used, it shall be not less than 0.0005 inch (12.7 m) thick. 3.4.3.1 Alternative to Masking When specified as an alternative to masking, the nitrided case may be removed by grinding from surfaces specified to be free fr
24、om nitriding. 3.5 Procedure 3.5.1 Loading Parts shall be placed on racks or suspended, so as to minimize distortion, and to allow all surfaces to be nitrided. If used, test specimens representing parts fabricated from the same alloy, and in same heat treatment condition, shall be placed in the worki
25、ng zone in a location adjacent to parts they represent as close as possible to the lowest and highest temperatures based on latest temperature uniformity tests. SAE INTERNATIONAL AMS2759/10A Page 4 of 9 3.5.2 If parts are masked, the specimen(s) shall be similarly masked on a portion of the surface.
26、 3.5.3 Nitriding of Parts Nitriding shall be accomplished in a process comprising one or more stages. The definition of a process stage is given in 8.5.2. 3.5.3.1 Nitriding Potential KN (See 8.5.3.) Shall be set, based on alloy and given application. Recommended ranges for typical alloys are given i
27、n 8.5.4. 3.5.3.2 Nitriding Potential Control For any nitriding potential setpoint value, the average KN value shall be maintained within limits shown in Figure 1 (for low potential range) and Figure 2 (for high potential range), after stabilization of the atmosphere. Stabilization for each stage of
28、the cycle shall be reached such that at least 60% of the stage time shall be conducted under stable conditions for short-duration processes (up to 6 hours) and at least 85% of the stage time shall be conducted under stable conditions for longer processes. Sample reading shall be taken from the outgo
29、ing atmosphere. The frequency of readings shall be not less than once every 30 seconds. FIGURE 1 - TOLERANCE LIMITS OF ACTUAL KN VALUE VS. SETPOINT VALUE FOR LOW NITRIDING POTENTIAL RANGE (SEE 3.5.3.2) SAE INTERNATIONAL AMS2759/10A Page 5 of 9 FIGURE 2 - TOLERANCE LIMITS OF ACTUAL KN VALUE VS. SETPO
30、INT VALUE FOR HIGH NITRIDING POTENTIAL RANGE (SEE 3.5.3.2) 3.5.3.3 Temperature Shall not exceed 1200 F (649 C). The recommended range is 915 to 1095 F (490 to 590 C). 3.5.3.4 Cooling The load shall be cooled from the nitriding temperature in a suitable protective atmosphere to a temperature not exce
31、eding 300 F (149 C). 3.6 Post-Nitriding Operations 3.6.1 Maskant Stripping Maskant materials shall be removed by non-embrittling and non-pitting methods. 3.7 Properties Parts shall conform to the following property requirements unless otherwise specified by the cognizant engineering organization. 3.
32、7.1 Hardness Testing shall be performed in accordance with ASTM A 370, ASTM E 92 or ASTM E 384. For conversion between scales and correlation with strength (See Notes 8.1 and 8.2). 3.7.1.1 Core Hardness In accordance with the requirements of the engineering drawing. SAE INTERNATIONAL AMS2759/10A Pag
33、e 6 of 9 3.7.1.2 Surface Hardness Shall meet the requirements shown in Table 1. Minimum surface hardness for alloys not shown in Table 1 shall be in accordance with engineering drawing requirements. TABLE 1 - MINIMUM SURFACE HARDNESS Alloy Minimum Hardness (HR15N) or Equivalent (See 8.2) Nitralloy 1
34、35 M 92.5 Nitralloy EZ 92.5 Nitralloy N 92.5 4140, 4340 85.5 D6, D6AC 85.5 H11 92.1 Other alloys Per drawing requirements 3.7.2 Microstructure Metallographic examination shall be made at a magnification not lower than 400X. The case shall exhibit a uniform distribution of nitrides, diminishing gradu
35、ally, from surface to core. There shall be no evidence of continuous nitride network in grain boundaries. Unless otherwise specified, when white layer is permitted, its maximum thickness shall be 0.0005 inch (12.7 m) for Class 1 and 0.001 inch (25.4 m) for Class 2, for steels specified in Table 1. F
36、or stainless steels, the maximum thickness of white layer shall be 0.0005 inch (12.7 m), regardless of class. 3.7.3 Case Depth In accordance with drawing requirements. It shall be the depth of the dark etching subsurface zone, determined metallographically. On those alloys which do not respond by da
37、rker etching, case depth shall be the depth below the surface at which microhardness is 10% higher than that of the core, as determined by a Knoop or a Vickers hardness traverse, in accordance with ASTM E 384. 3.7.3.1 Effective Case Depth Where specified, it shall be in accordance with drawing requi
38、rements. It shall be the depth at which the hardness values specified in Table 2, converted from microhardness, are obtained in accordance with ASTM E 384. Effective case depth for alloys not shown in Table 2 shall be in accordance with drawing requirements. Where no ranges or tolerance limits are s
39、pecified, the acceptance limits shall be 0.001 inch (25.4 m) or 10%, whichever is greater, of the case depth on the engineering drawing. TABLE 2 HARDNESS AT EFFECTIVE CASE DEPTH Specification Alloy Minimum Hardness (HRC Converted)(See 8.2) AMS 6470, AMS 6471. AMS 6472 Nitralloy 135 M 50 Nitralloy EZ
40、 50 AMS 6475 Nitralloy N 50 AMS 6382; AMS 6414; AMS 6415 4140; 4340 50 AMS 6431; AMS 6439 D6; D6AC 50 AMS 6485, AMS 6487, AMS 6488 H11 60 Other grades Per drawing requirements 4. QUALITY ASSURANCE PROVISIONS The responsibility for inspection, classification of tests, sampling, approval, entries, rec
41、ords, and reports shall be in accordance with AMS 2759 and as specified in 4.1. SAE INTERNATIONAL AMS2759/10A Page 7 of 9 4.1 Classification of Tests The classification of acceptance, periodic, and preproduction tests, as well as sampling, shall be in accordance with AMS 2759. 4.1.1 Acceptance Tests
42、 In addition to tests specified in AMS 2759, tests to determine conformance to requirements of 3.7.1, 3.7.2 and 3.7.3 shall be performed on parts from each nitrided lot, or on process control specimens, supplied by the purchaser. The specimens shall be processed with the parts they represent. 4.2 Sa
43、mpling and Testing Shall be in accordance with AMS 2759. 5. PREPARATION FOR DELIVERY Shall be in accordance with AMS 2759. 6. ACKNOWLEDGMENT The process vendor shall mention this specification number and its revision letter in all quotations, when acknowledging purchase orders and on certifications.
44、 7. REJECTIONS Parts not processed in accordance with this specification or modifications authorized by the cognizant engineering organization, and parts not meeting specified requirements, shall be subject to rejection and shall be submitted for disposition in accordance with purchasers procedures
45、of nonconformance. 8. NOTES Also see AMS 2759. 8.1 Tensile strength to hardness conversions are presented in ASTM A 370. 8.2 Hardness conversion tables for metals are presented in ASTM E 140. 8.3 On austenitic and precipitation-hardening stainless steels, the diffusion layer may form a sharp border
46、with the underlying matrix, exhibiting no transition zone from case to core. On such steels, the case depth is defined as the visual, dark etching zone. 8.4 Limitations on Grinding The grinding operation, if applicable, should not reduce the effective case depth to below specification requirements.
47、As guidance, the expected growth from side to side, e.g., across a diameter, is equal to approximately 70% of the thickness of the white layer. 8.5 Terms used in AMS are clarified in ARP1917 and as follows: 8.5.1 Compound Layer External, non-etching portion of nitrided layer, composed of compact eps
48、ilon or gamma prime nitrides or a combination thereof, commonly referred to as “white layer”. SAE INTERNATIONAL AMS2759/10A Page 8 of 9 8.5.2 Process Stage A stage is a part of a process cycle, defined by temperature, time, atmosphere composition and nitriding potential. It shall differ from other s
49、tages by at least one of the above parameters, other than time, to be recognized as a stage. 8.5.3 Nitriding Potential The nitriding potential is a measure of the nitriding capability of the nitriding atmosphere, controlling surface nitrogen concentration in steel at a given temperature, and is described by Equation 1: ()2/3HNHN23PPK =(Eq. 1) Where: PNH3= the partial pressure of ammonia in the outgoing atmosphere, and PH2=
