SAE AMS 2753B-1991 Liquid Salt Bath Ferritic Nitrocarburizing Non-Cyanide Bath R(1995)

SAESAESAESAE LIQUID SALT BATH FERRITIC NITROCARBURIZING Non-Cyanide Bath AMS 2753B Issued 1 JAN 1985 Revised 1 OCT 1991 Superseding AMS 2753A AEROSPACE MATERIAL SPECIFICATION SAESAESAESAE The Engineering Society For Advancing Mobility Land Sea Air and Space® 400 Commonwealth Drive, Warrendale, PA 15096-0001 I N T E R N A T I O N A L An American National Standard SAE Technical 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 therefrom, 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 1991 Society of Automotive Engineers, Inc. All rights reserved. Printed in U.S.A. 1. SCOPE: 1.1 Purpose: This specification covers the engineering requirements for producing a thin epsilon-iron nitride case on parts by means of a low- temperature, aerated, fused salt bath process and the properties of the case. 1.2 Application: This procedure has been used typically for increasing the resistance to wear and fatigue on ferrous alloys including carbon steels, low-alloy steels, oil- and air-hardening tool steels, and corrosion-resistant steels, cast irons, and ferrous powder metal products, but usage is not limited to such applications. 1.2.1 This process is not recommended for use on parts which have been plated with silver, copper, zinc, or cadmium or on parts having copper alloy inserts. 1.3 Safety - Hazardous Materials: While the materials, methods, applications, and processes described or referenced in this specification 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 measures to ensure the health and safety of all personnel involved. Copyright SAE International Provided by IHS under license with SAE Licensee=Messier Dowty/5905381001 Not for Resale, 10/12/2005 21:04:00 MDTNo reproduction or networking permitted without license from IHS --``,`,,,`,`,,,,,,``,,,,,,,,,``-`-`,,`,,`,`,,`--- SAE AMS 2753BAMS 2753B 2. APPLICABLE DOCUMENTS: The following publications form a part of this specification to the extent specified herein. The latest issue of SAE publications shall apply. The applicable issue of other publications shall be the issue in effect on the date of the purchase order. 2.1 SAE Publications: Available from SAE, 400 Commonwealth Drive, Warrendale, PA 15096-0001. 2.1.1 Aerospace Material Specifications: AMS 2759 Heat Treatment of Steel Parts, General Requirements 2.1.2 Aerospace Recommended Practices: ARP1820 Chord Method of Evaluating Surface Microstructural Characteristics 2.1.3 SAE Standards: SAE J423 Methods of Measuring Case Depth 2.2 ASTM Publications: Available from ASTM, 1916 Race Street, Philadelphia, PA 19103-1187. ASTM E 140 Hardness Conversion Tables for Metals (Relationship Between Brinell Hardness, Vickers Hardness, Rockwell Hardness, Rockwell Superficial Hardness, and Knoop Hardness) ASTM E 384 Microhardness of Materials 2.3 U.S. Government Publications: Available from Standardization Documents Order Desk, Building 4D, 700 Robbins Avenue, Philadelphia, PA 19111-5094. 2.3.1 Military Standards: MIL-STD-2073-1 DOD Materiel, Procedures for Development and Application of Packaging Requirements 2.4 ASM Publications: Available from ASM International, Materials Park, OH 44073 ASM Handbook, Metallography and Microstructure, 9th Edition. - 2 - Copyright SAE International Provided by IHS under license with SAE Licensee=Messier Dowty/5905381001 Not for Resale, 10/12/2005 21:04:00 MDTNo reproduction or networking permitted without license from IHS - - ` ` , ` , , , ` , ` , , , , , , ` ` , , , , , , , , , ` ` - ` - ` , , ` , , ` , ` , , ` - - - SAE AMS 2753BAMS 2753B 3. TECHNICAL REQUIREMENTS: 3.1 Processing Equipment: 3.1.1 Nitrocarburizing Salts: Shall consist primarily of a mixture of alkali metal cyanates and carbonates. 3.1.2 Salt Bath: The cyanate content of the bath shall be controlled within the range 34 - 38% by weight, determined as cyanate ion. 3.1.3 Parts to be nitrocarburized should be processed in a salt bath retort-type furnace conforming to AMS 2759. Furnace temperature uniformity requirements shall be ±15 °F (±8 °C). 3.1.4 Furnace Controls: Shall conform to AMS 2759. 3.1.5 Thermocouples: When load thermocouples are required, they shall be sheath protected to prevent deterioration due to immersion in nitrocarburizing salts. 3.1.6 Aeration: The bath shall be aerated with clean, dry, oil-free compressed or plant air. A desiccant air dryer, a flowmeter for measuring air flow, a gauge for air pressure, and a sparging ring are required equipment. The air flow and pressure shall be in accordance with the salt producer's recommendations. 3.2 Pretreatment: 3.2.1 Hardening: Parts requiring core hardening prior to nitrocarburizing, shall be heat treated in accordance with AMS 2759, or other procedure acceptable to purchaser, to the required core hardness. Tempering for the specified core hardness shall be done at a temperature not lower than 20 °F (11 °C) above the highest nitrocarburizing temperature to be used. 3.2.2 Surface Condition: Prior to nitrocarburizing, parts shall be clean and free of scale, oxide, entrapped sand, mold or core sand material, metal particles, oil, or grease. Parts must be completely dry. Surfaces to be nitrocarburized shall be mechanically or chemically cleaned subsequent to stress relieving and prior to nitrocarburizing. 3.2.3 Stress Relief: Parts in which residual stresses may have been introduced by prior mechanical working or other causes and consequently may crack or change dimensionally during nitrocarburizing shall be stress relieved prior to final part machining. Stress relief shall be performed in accordance with AMS 2759 at a temperature not lower than 20 °F (11 ºC) above the nitrocarburizing temperature. 3.3 Procedures: 3.3.1 Preheating: Parts shall be preheated in air to a temperature not higher than 750 ºF (399 ºC), to ensure drying, to maintain bath temperature, and to avoid thermal shock upon immersion in the nitrocarburizing salt. - 3 - Copyright SAE International Provided by IHS under license with SAE Licensee=Messier Dowty/5905381001 Not for Resale, 10/12/2005 21:04:00 MDTNo reproduction or networking permitted without license from IHS - - ` ` , ` , , , ` , ` , , , , , , ` ` , , , , , , , , , ` ` - ` - ` , , ` , , ` , ` , , ` - - - MS 27530 SAE AJ4S 2753B 3.3.2 Nitrocarburizing: Parts shall be immersed and held at temperature in the aerated cyanate bath as follows: Material Time Approximate min Temperature max "F 'C Carbon and Low- Alloy Steels 1 hour 2 hours 1070 577 Tool and Die Steels 5 minutes 3 hours 1000 538 Corrosion and Heat Resistant Steels (3.3.2.1) 15 minutes 2 hours 1070 577 Ductjle, Malleable, and Gray Cast Iron 1 hour 3 hours 1070 577 Ferrous Powder Metal Products 30 minutes 2 hours 1070 577 3.3.2.1 Nitrocarburizing temperature should be at least 20 'F (11 'C) below final temperlng temperature or precipitation hardening temperature to maintain base material hardness but shall not be lower than 1000 'F (538 “0. 3.3.3 Quenching: Following nitrocarburizing, parts shall be intermediate quenched in a fused salt bath in a temperature range of 650 to 750 "F (343 to 399 "0. After parts have stabilized at the bath temperature set pofnt, water quench or air cool. 3.4 Properties: Nitrocarburized parts shall conform to the following requirements, determined on parts or on test specimens as in 4.3.1: 3.4.1 Test for Compound Layer Presence: The required presence of a compound layer on non-austenitic steels and cast irons shall be confirmed by means of a chemical spot test. A drop of copper ammonium chloride (3.4.1.1) or copper sulfate solution (3.4.1.2) applied to a clean nitrocarburized surface of a part shall turn a reddish-brown color after 15 seconds. If copper plates out on the surface after this procedure, the compound layer is not present and the part is subject to rejection. 3.4.1.1 Copper ammonium chloride solution: dissolve 100 grams cupric chloride (CuC12 - 2H20) in distilled water to make one liter. Add ammonium hydroxide to form a copper ammonium chloride complex. 3.4.1.2 Copper sulfate solution: dissolve 40 grams copper sulfate (CuSO4 - 5H20) fn 1000 mL distilled water and 5 mL wetting agent, (i.e. glycerin); pH shall be 3.5 - 4.1. - 4 - Copyright SAE International Provided by IHS under license with SAE Licensee=Messier Dowty/5905381001 Not for Resale, 10/12/2005 21:04:00 MDTNo reproduction or networking permitted without license from IHS - - ` ` , ` , , , ` , ` , , , , , , ` ` , , , , , , , , , ` ` - ` - ` , , ` , , ` , ` , , ` - - - SAE AMS 2753BAMS 2753B 3.4.2 Depth of Compound Layer: Shall be as follows, determined in accordance with the taper or step grind procedures of SAEJ423 or ARP1820, microscopic method at not less than 500X magnification. Compound Layer Thickness Material Inch Millimeter min max min max Carbon Steel Corrosion & Heat 0.00015 0.0010 0.0038 0.025 Resistant Steels 0.00015 0.0010 0.0038 0.025 Low-Alloy Steel 0.00015 0.0010 0.0038 0.025 Tool and Die Steels 0.0001 0.0005 0.0025 0.012 Cast Iron 0.00015 0.0010 0.0038 0.025 Ferrous Powder Metal Products (minimum density 7.0 gm/cc) 0.00015 0.0010 0.0038 0.025 3.4.3 Quality of Compound Layer: 3.4.3.1 Not less than three fields shall be examined at 500X magnification employing acceptable quantitative metallographic procedures of line intercept or grid analysis (as described in ASM Handbook, 9th Edition, Metallography and Microstructure, pages 123 to 134). The upper half of the total compound-thickness, as in 3.4.2, shall not contain more than 50% residual porosity and oxides in any one field viewed. The compound layer at the substrate interface and the lower quarter of the total compound thickness shall not exhibit residual porosity and oxides exceeding 5% for steel and corrosion-resistant steel components and 15% for cast iron components. 3.4.3.2 For parts treated in liquid ferritic nitrocarburizing baths using sulfur bearing salts, the resultant compound layer shall be free of sulfur. Quantitative surface analysis shall be done to verify the absence of sulfur. 3.4.4 Case Hardness: Shall be as follows, determined by microhardness measurements at a depth of 0.001 inch (0.025 mm) from the treated surface in accordance with ASTM E 384 or by the chord method of ARP1820 on prepared cross sections of the nitrocarburized case using Knoop or other appropriate hardness tester acceptable to the cognizant engineering activity. Material Hardness, minimum HK1OO or equivalent Carbon Steels 300 Low-Alloy Steels 460 Tool & Die Steels 600 Cast Iron (Gray, Ductile, or Malleable) 300 Corrosion & Heat Resistant Steel 600 Ferrous Powder Metal Products (minimum density 7.0 g/cc) 300 - 5 - Copyright SAE International Provided by IHS under license with SAE Licensee=Messier Dowty/5905381001 Not for Resale, 10/12/2005 21:04:00 MDTNo reproduction or networking permitted without license from IHS --``,`,,,`,`,,,,,,``,,,,,,,,,``-`-`,,`,,`,`,,`--- SAE AMS 2753BAMS 2753B 4. QUALITY ASSURANCE PROVISIONS: 4.1 Responsibility for Inspection: The processor of treated parts shall supply all samples for processor's tests and shall be responsible for performing all required tests. Purchaser reserves the right to sample and to perform any confirmatory testing deemed necessary to ensure that the parts conform to the requirements of this specification. 4.2 Classification of Tests: 4.2.1 Acceptance Tests: Tests for core hardness (3.2.1), presence of compound layer (3.4.1), depth of compound layer (3.4.2), quality (3.4.3), and case hardness (3.4.4) are acceptance tests and shall be performed on each heat treatment lot. 4.2.2 Periodic Tests: Tests for cyanate content (3.1.2) are periodic tests and shall be performed at a frequency selected by the vendor unless frequency of testing is specified by purchaser. 4.2.3 Preproduction Tests: Tests for all technical requirements are preproduction tests and shall be performed prior to or on the first-article shipment of nitrocarburized parts to a purchaser, when a change in material and/or processing requires reapproval as in 4.4.2, and when purchaser deems confirmatory testing to be required. 4.2.3.1 For direct U.S. Military procurement, substantiating test data and when requested, preproduction test material shall be submitted to the cognizant agency as directed by the procuring activity, contracting officer, or request for procurement. 4.3 Sampling and Testing: Not less than one sample shall be processed for evaluation for each test requirement: 4.3.1 Evaluation Samples: Test pins or specimens of the same nominal composition as the parts shall be processed with the work when required by purchaser. 4.4 Approval: 4.4.1 Nitrocarburized parts shall be approved by purchaser before parts for production use are supplied, unless such approval be waived by purchaser. Results of tests on production parts shall be essentially equivalent to those on the approved sample parts. 4.4.1.1 Specimens of the same nominal composition and heat treat condition (See 4.3.1) may be used for destructive evaluation in lieu of actual parts if acceptable to the cognizant quality assurance activity. - 6 - Copyright SAE International Provided by IHS under license with SAE Licensee=Messier Dowty/5905381001 Not for Resale, 10/12/2005 21:04:00 MDTNo reproduction or networking permitted without license from IHS --``,`,,,`,`,,,,,,``,,,,,,,,,``-`-`,,`,,`,`,,`--- SAE AMS 2753BAMS 2753B 4.4.2 Vendor shall use manufacturing procedures, processes, and methods of inspection on production parts which are essentially the same as those used on the approved sample parts. If necessary to make any change in established limits of compound layer or in nitrocarburizing procedures, vendor shall submit for reapproval of the process a statement of the proposed changes in processing and, when requested, sample nitrocarburized parts, test pins, or both. Production parts treated by the revised procedure shall not be shipped prior to receipt of reapproval. 4.4.3 The processer shall have a copy of the procedure available for review by purchaser's cognizant quality assurance organization. It shall include a full description of all equipment and procedures used to process parts. 4.5 Reports: The processor of nitrocarburized parts shall furnish with each shipment a report stating that the parts have been processed and tested in accordance with the requirements of this specification and that they conform to the acceptance test requirements. This report shall include the purchase order number, lot number, AMS 2753B, part number, and quantity. 4.6 Resampling and Retesting: If any specimen used in the above tests fails to meet the specified requirements, disposition of the parts may be based on the results of testing three additional specimens for each original nonconforming specimen. Failure of any retest specimen to meet the specified requirements shall be cause for rejection of the parts represented. Results of all tests shall be reported. 5. PREPARATION FOR DELIVERY: 5.1 Packaging: 5.1.1 Parts shall be handled and packaged to ensure that the required physical characteristics of the nitrocarburized parts are preserved. 5.1.2 Packages of nitrocarburized parts shall be prepared for shipment in accordance with commercial practice and in compliance with applicable rules and regulations pertaining to the handling, packaging, and transportation of the parts to ensure carrier acceptance and safe delivery. 5.1.3 For direct U.S. Military procurement, packaging shall be in accordance with MIL-STD-2073-1, Commercial Level, unless Level A is specified in the request for procurement. 6. ACKNOWLEDGMENT: A vendor shall mention this specification number and its revision letter in all quotations and when acknowledging purchase orders. - 7 - Copyright SAE International Provided by IHS under license with SAE Licensee=Messier Dowty/5905381001 Not for Resale, 10/12/2005 21:04:00 MDTNo reproduction or networking permitted without license from IHS - - ` ` , ` , , , ` , ` , , , , , , ` ` , , , , , , , , , ` ` - ` - ` , , ` , , ` , ` , , ` - - - SAE AMS 2753BAMS 2753B 7. REJECTIONS: Parts on which the compound layer does not conform to this specification, or to modifications authorized by purchaser, will be subject to rejection. 8. NOTES: 8.1 Marginal Indicia: The (R) symbol is used to indicate technical changes from the previous issue of this specification. 8.2 Diffusion in carbon steels, determined under microscopic examination, has an acicular appearance, when nital etched, after the sample has been heated at 570 ºF ± 10 (299 ºC ± 6) for not less than 1 hour. The acicular zone represents one-third to one-half of the total nitrogen penetration. Alloy steels, when etched with nital, will reveal a dark zone which represents approximately one-quarter of the total nitrogen diffusion. Acicular structure is not apparent in alloy steels. Etchants for other materials shall be acceptable to purchaser. 8.3 Compound layer or zone thickness up to 0.0004 inch (0.010 mm) can be measured nondestructively by X-ray diffraction techniques. 8.4 Testing of the compound layer for the presence of sulfur can be accomplished with a scanning microprobe analysis or an Auger analysis. 8.5 Dimensions and properties in inch/pound units and the Fahrenheit temperatures are primary; dimensions and properties in SI units and the Celsius temperatures are shown as the approximate equivalents of the primary units and are presented only for information. 8.6 For direct U.S. Military procurement, purchase documents should specify not less than the following: Title, number, and date of this specification Part number of parts to be nitrocarburized Quantity of parts to be nitrocarburized Level A packaging, if required (See 5.1.3). 8.7 Processes meeting the requirements of this specification have been classified under Federal Supply Classification (FSC) 9999. This specification is under the jurisdiction of AMS Committee "B". - 8 - Copyright SAE International Provided by IHS under license with SAE Licensee=Messier Dowty/5905381001 Not for Resale, 10/12/2005 21:04:00 MDTNo reproduction or networking permitted without license from IHS - - ` ` , ` , , , ` , ` , , , , , , ` ` , , , , , , , , , ` ` - ` - ` , , ` , , ` , ` , , ` - - -