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 theref
2、rom, 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 2007 SAE International All rights reserved. No part of this publication ma
3、y 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: 724-776-4970 (outside USA)
4、Fax: 724-776-0790 Email: CustomerServicesae.org SAE WEB ADDRESS: http:/www.sae.org AMS 2759/12A AEROSPACE MATERIAL SPECIFICATION Issued 2007-07 Revised 2007-11 Superseding AMS 2759/12 Gaseous Nitrocarburizing, Automatically Controlled by Potentials RATIONALE AMS 2759/12A is the result of a correctio
5、n to Table 1 and 3.6.5. 1. SCOPE 1.1 Purpose This specification covers the requirements for producing a continuous compound layer with controlled phase composition by means of a gaseous process, automatically controlled to maintain set values of the nitriding and carburizing potentials that determin
6、e properties of the nitrocarburized surface. Automatic control is intended to ensure repeatability of nitrogen and carbon content of the compound layer which establishes properties such as wear and corrosion resistance, ductility and fatigue strength. 1.2 Application 1.2.1 The nitrocarburizing proce
7、ss has been used typically for enhancement of wear resistance and fatigue strength, as well as corrosion resistance in ferrous alloys but usage is not limited to such applications. Nitrocarburizing can be selectively applied to only those areas that require nitrocarburizing. 1.2.2 Specifically, this
8、 process is recommended for those applications where control of phase composition is required. 1.3 Classification The nitrocarburizing process described herein is classified as follows: 1.3.1 Class 1 - Porosity not exceeding 15% of the thickness of the compound (white) layer 1.3.2 Class 2 - Porosity
9、 above 10% but not exceeding 50% of the thickness of the white layer 1.3.3 If no class is specified, no limitations shall be placed on the degree of porosity 1.4 Safety - Hazardous Materials While the materials, methods, applications, and processes described or referenced in this specification may i
10、nvolve the use of hazardous materials, this specification does not address the hazards which may be involved in such use. It is the 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 heal
11、th and safety of all personnel involved. SAE AMS 2759/12A - 2 - 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
12、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,
13、 Tel: 877-606-7323 (inside USA and Canada) or 724-776-4970 (outside USA), www.sae.org. AMS 2418 Plating, Copper AMS 2429 Masking, Bronze Plate, Nitriding Stop-Off, 90Cu-10Sn AMS 2750 Pyrometry AMS 2759 Heat Treatment of Steel Parts, General Requirements ARP1820 Chord Method of Evaluating Surface Mic
14、rostructural Characteristics SAE J423 Methods of Measuring Case Depth SAE J864 Surface Hardness Testing With Files 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, www.astm.org. ASTM D 1193 Reagent Wat
15、er ASTM E 384 Microhardness of Materials 2.3 ASM Publications Available from ASM International, 9639 Kinsman Road, Materials Park, OH 44073-0002, Tel: 800-336-5152 (inside U.S. and Canada), 440-338-5151 (outside USA), www.asm-intl.org. ASM Handbook, 9thEdition, Metallography and Microstructures 3. T
16、ECHNICAL REQUIREMENTS 3.1 Processing Equipment Parts to be nitrocarburized shall be processed in a sealed retort type furnace with forced atmosphere circulation or a furnace with a sealed chamber and may be equipped with an integral quench facility conforming to AMS 2759. The furnaces shall be equip
17、ped with gas analyzing equipment capable of measuring the concentration of reactive gases in the retort, necessary for determination of the nitriding and carburizing potentials, based on reactions referenced in 8.5. The furnace temperature uniformity requirements shall be 15 F ( 8 C). 3.1.1 Atmosphe
18、re The nitrocarburizing atmosphere shall consist of a mixture of gases supplying nitrogen, and supplying carbon. Any mixture of gases is acceptable, as long as it enables effective control of the nitriding and carburizing potentials. 3.1.2 Thermocouples Load thermocouples, if used, shall be sheath-p
19、rotected to prevent deterioration due to furnace atmospheres. Pyrometry shall conform to AMS 2750. SAE AMS 2759/12A - 3 - 3.1.3 Shutdowns and Alarms The system shall be capable of automatically and safely shutting down the process in the event of any malfunction of the equipment such as power failur
20、e, interruption of gas flow or any parameters exceeding their tolerance limits to prevent any damage to parts being processed. 3.2 Pretreatment 3.2.1 Parts requiring hardening to a specified strength level shall be heat treated in accordance with AMS 2759 or as specified by drawing or cognizant engi
21、neering organization, to the required core hardness prior to nitrocarburizing. In cases of discrepancy, the requirements specified on the engineering drawing shall take precedence over those on the purchase order. Unless otherwise approved by the cognizant engineering organization, tempering tempera
22、ture shall be at least 50 F (28 C) above the nitrocarburizing temperature. 3.2.2 Surface Condition Parts shall be clean and free from grease, oil, and other contaminants. Parts shall be dry. 3.2.3 Stress Relieving Unless otherwise specified, parts that have been ground, straightened, or otherwise me
23、chanically worked after hardening, shall be stress relieved prior to nitrocarburizing, in accordance with AMS 2759/11. The stress relieving temperature shall not be higher than 50 F (28 C) below the tempering temperature. Surfaces to be nitrocarburized shall be cleaned by any effective method subseq
24、uent to stress relieving and prior to nitrocarburizing, to meet the requirements of 3.2.2. 3.2.4 Selective Nitrocarburizing Surfaces that require protection from nitrocarburizing shall be masked by a suitable maskant, e.g., copper plating (AMS 2418), bronze plating (AMS 2429) or by alternative metho
25、ds, acceptable to the cognizant engineering organization. Copper plate shall be fine-grained and nonporous, 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 (0.0125 mm) in thickness. 3.2.4.1 Alternative to Masking If authorized by the
26、 cognizant engineering organization, parts may be nitrided all over and subsequently the case removed from areas not to be nitrocarburized. 3.3 Procedure 3.3.1 Loading Parts shall be placed on racks or suspended, so as to minimize distortion, and to allow all surfaces to be nitrocarburized. If used,
27、 test coupons representing parts fabricated from the same alloy, with the same surface finish and in the same heat treatment condition, shall be placed in the working zone of the furnace, in a location adjacent to the parts they represent, as close as possible to the lowest and highest load temperat
28、ures based on the most recent temperature uniformity survey. 3.3.2 Preheating Parts may be preheated in air to a temperature not higher than 850 F (454 C) 3.4 Nitrocarburizing of parts. Nitrocarburizing shall be carried out in an automated mode, maintaining set parameters of temperature and nitridin
29、g and carburizing potentials, selected from Table 1. For any intermediate temperatures potential values may be interpolated graphically. See 8.8. The two potentials shall be selected in pairs from within the specified limit ranges. SAE AMS 2759/12A - 4 - TABLE 1 - PROCESS PARAMETERS ENSURING THE FOR
30、MATION OF AN EPSILON-TYPE COMPOUND LAYER WITH TWO RANGES OF POROSITY LEVELS, IN ACCORDANCE WITH 1.3 Class 1 Not exceeding 15% of thickness of white layer Class 2 Above 10% but not exceeding 50% of thickness of white layer Process Temperature KNKCKNKCMaterial F C Process Time hr min max min max min m
31、ax min max Group 1* 1040 560 3 - 6 2.13 2.41 0.57 0.69 2.48 2.68 0.49 0.54 1075 579 2 - 5 1.50 1.60 1.10 1.22 1.68 1.78 0.86 0.94 Group 2* 980 527 6 - 30 4.51 5.55 0.16 0.24 6.03 7.10 0.09 0.13 Group 3* 1060 571 3 - 10 1.82 2.10 0.76 0.99 2.22 2.64 0.48 0.68 For recommended ranges of nitriding and c
32、arburizing potentials at other temperatures, see 8.8. Temperatures shown are not firm requirements, however, once a temperature selected, both potential values shall be within specified limits for the given temperatures. * Group 1 - HSLA, carbon steels * Group 2 - 4140, 4340, Nitralloy 135M * Group
33、3 - Cast iron 3.5 Cooling Following nitrocarburizing treatment, depending on the available equipment, parts shall be either furnace cooled or quenched in oil, water or soluble oil solutions, polymer quenchants, inert or nitrocarburizing atmospheres, or air. 3.6 Properties of Nitrocarburized Layers G
34、aseous nitrocarburized components shall meet the following requirements, determined on either components or test specimens made from the same material and in the same heat treatment condition and processed in the same nitrocarburizing cycle. 3.6.1 Thickness of compound layers shall conform to limits
35、 shown in Table 2, determined in accordance with the procedure of SAE J423 or ARP1820 microscopic methods, at magnification of min. 500X. TABLE 2 - COMPOUND LAYER THICKNESS Thickness (inch) Thickness (mm) min max min maxCarbon and HSLA steel 0.0002 0.0010 0.0051 0.025 Low Alloy Steel 0.0002 0.0010 0
36、.0051 0.025 Tool Steel 0.0001 0.0006 0.0025 0.015 Cast Iron 0.0002 0.0010 0.0051 0.025 3.6.2 Presence of Compound Layer The presence of compound layer on non-austenitic steels and cast irons shall be determined by a chemical spot test. The test shall be performed by applying a drop of copper sulfate
37、 solution complying with 3.6.3 or copper ammonium chloride solution complying with 3.6.4 to a clean nitrocarburized surface. If, after 15 seconds, the spot to which the drop was applied turns red, due to the deposition of copper, compound layer is not present and the part is subject to rejection. SA
38、E AMS 2759/12A - 5 - 3.6.3 Preparation of Copper Sulfate Solution Dissolve approximately 40 grams copper sulfate (CuSO45H2O) in 1 liter of reagent water (See ASTM D 1193 Type II). A wetting agent (e.g., 5 mL glycerin) may be added. The pH shall be 3.5 to 4.1. 3.6.4 Preparation of Ammonium Chloride S
39、olution Dissolve approximately 100 grams of cupric chloride (CuCl22H2O) in reagent water to make 1 liter. Add sufficient ammonium hydroxide solution (NH4OH) to form a brilliant blue copper ammonium chloride complex solution. 3.6.5 Compound Layer Structure At least three fields of view shall be exami
40、ned, using magnification of minimum 500X. Porosity shall not exceed 15% of the total thickness of the compound layer for Class 1 and shall be above 10% but not exceeding 50% of the total thickness of the compound layer for Class 2. Porosity shall be concentrated in the external (upper) half of the w
41、hite layer. Porosity in the lower quarter of the compound layer, at the interface with the substrate shall not exceed 5% for all steel grades, and 15% for cast irons. Extent of porosity shall be measured. See 8.7 for an acceptable method. 3.6.6 Compound layer hardness shall be measured in accordance
42、 with SAE J864 test for file hardness and shall be equivalent of 60 HRC or higher. Alternatively, surface hardness may be measured by a Vickers or a Knoop tester under a light test load, if specified by the cognizant engineering organization. In such cases, the surface hardness shall meet requiremen
43、ts of the engineering drawing or purchase order. 3.6.7 Diffusion zone depth. If specified by the cognizant engineering organization, diffusion case depth shall be measured and recorded. For carbon steels, diffusion case depth is determined visually with the aid of a metallurgical microscope, as the
44、distance from the surface to the depth at which needle-like nitride precipitations are still visible. On rapidly cooled carbon steels, where needle precipitations are not visible, diffusion depth can be determined by appropriate application of etchants in addition to Nital. For alloy steels, case de
45、pth is determined by a microhardness traverse, defined as effective case depth to a specified hardness or total case depth to where the hardness drops to 50 HK or 50 HV above core hardness. If the engineering drawing specifies a case depth, but does not specifically state that it is to be effective
46、at a given hardness level, total case depth shall apply. Where “etched case depth“ or “visual case depth” is specified, it shall be the distance measured from the surface in the direction of the core to the location where the zone darkened by etching ends. 3.6.8 Diffusion Zone (Case) Hardness If req
47、uired by the cognizant engineering organization, shall be determined by a microhardness measurement, performed at a depth of 0.002 inch (0.05 mm) from the nitrocarburized surface, in accordance with ASTM E 384 or by the chord method of ARP 1820, on a mounted and polished cross-section of the nitroca
48、rburized case. The Knoop or Vickers indenter may be used, as specified by the cognizant engineering organization. TABLE 3 - DIFFUSION ZONE MINIMUM HARDNESS Material Hardness HK100 Hardness HV100 Carbon Steel 300 290 Low Alloy Steel 460 440 Tool Steels 600 565 Cast Iron 300 290 SAE AMS 2759/12A - 6 -
49、 3.7 Records A record (written or archived) shall be kept for each furnace load. The information on the combination of documents shall include: equipment identification, approved personnel identification, date, part number or product identification, number of parts, alloy, purchase order, lot identification, reference to this specification and/or other applicable specifications, actual times and temperatures used, as well as nitriding and carburizing potentials. When applicable, other atmosphere control parameters, quench delay, quenchant type, polymer
