Sae Ams2769b (2014)

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AMS2769 REV. B
AEROSPACE MATERIAL
SPECIFICATION Issued 1996-02
Revised 2009-12
Reaffirmed 2014-04
Superseding AMS2769A
Heat Treatment of Parts in a Vacuum
RATIONALE
AMS2769B has been reaffirmed to comply with the SAE five-year review policy.
1. SCOPE
1.1 Purpose
This specification establishes the requirements and procedures for heat treating parts (See 8.4) in a vacuum/partial
pressure.
1.2 Application
This process has been used typically for the heat treatment of carbon and alloy steels, tool steels, corrosion-resistant
steels, precipitation-hardening steels, super alloys, titanium, and other nonferrous alloys, but usage is not limited to such
applications.
1.2.1 Heat treatment as used in this specification includes solution treatment, homogenizing, austenitizing, annealing,
normalizing, hardening, tempering, aging, and stress relieving. This specification does not cover processes such
as melting, brazing, diffusion bonding, coating, carburizing, or nitriding.
1.2.2 The objective of this process is to produce heat treated parts which are free from surface contamination and alloy
depletion. Such parts may not necessarily have a bright surface.
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.
__________________________________________________________________________________________________________________________________________
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SAE INTERNATIONAL AMS2769B Page 2 of 19
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 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, Tel: 877-606-7323 (inside
USA and Canada) or 724-776-4970 (outside USA), www.sae.org.
AMS2750 Pyrometry
ARP1962 Training and Approval of Heat-Treating Personnel
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 MNL 12 Manual on the Use of Thermocouples in Temperature Measurement
2.3 National Fire Protection Association (NFPA)
Available from the National Fire Protection Agency, 1 Batterymarch Park, Quincy, MA 02169-7471, Tel: 617-770-3000,
www.nfpa.org.
NFPA 86D Standard for Industrial Furnaces Using Vacuum as an Atmosphere
2.4 CGA Publications
Available from Compressed Gas Association, Inc., 4221 Walney Road, 5th Floor, Chantilly, VA 20151-2923, Tel: 703-788-
2700, www.cganet.com.
CGA G-5.3 Commodity Specification for Hydrogen

CGA G-9.1 Commodity Specification for Helium
CGA G-10.1 Commodity Specification for Nitrogen
CGA G-11.1 Commodity Specification for Argon
3. TECHNICAL REQUIREMENTS
3.1 Furnace Equipment
The equipment shall conform to the requirements of applicable heat treat specifications. The furnace components shall
result in no detrimental metallurgical effects on the material processed during a normal production run as a result of
vaporization or chemical reaction between the furnace components and the gases used to maintain partial pressure in the
furnace.
3.1.1 Vacuum System
The vacuum pumping system shall have sufficient pumping capacity to evacuate the furnace to a pressure within the
recommended range indicated in Table 1 for the materials being processed, and to maintain the desired level of vacuum
during the entire heat treating process, including periods when a partial pressure is maintained using a controlled flow of
inert gas.

3.1.1.1 Vacuum Sensing Equipment
The vacuum furnace shall be equipped with at least one gauge capable of sensing and recording the pressure in the
vacuum heating chamber of the furnace at any point within the equipment operating temperature range required for the
material and processing being performed. Vacuum sensing equipment shall be calibrated or adjusted in accordance with
manufacturer’s specification. Recommended gauges are shown in Table 2.
3.1.1.2 Vacuum Gauge Calibration
The method of vacuum gauge calibration shall be in accordance with manufacturer’s specification and be acceptable to
purchaser. For furnaces used for processing materials at pressures of 1 × 10-3 torr (0.13 Pa) or lower, vacuum gauges
shall be calibrated every three months; otherwise vacuum gauges shall be calibrated at least annually, unless conditions
necessitate more frequent calibrations.
3.1.1.3 Leak Rate
Leak testing shall be performed weekly at ambient or elevated temperature. The leak rate shall not exceed the maximum
permissible rate specified in Table 3 at a chamber pressure of 50 microns (50 µm) or lower. Initial leak rate shall be
determined after closing the vessel and evacuation to at least 50 microns (50 µm). After reaching the initial evacuation
level setpoint for the process being performed, all valves to the vessel chamber shall be closed, the initial pressure
recorded, and a second reading of pressure made not less than 15 minutes after the first reading. Leak rate is determined
by dividing the rise in pressure (difference between final reading and initial reading) by the test time in hours. Leak rate is
expressed as microns (µm) per hour.
3.1.1.4 As an alternative to the test of 3.1.1.3 vacuum furnaces which have an integral oil tank shall pass a surface
contamination test in accordance with the following requirements:
3.1.1.4.1 Furnaces for heating steel parts above 1250 ºF (677 ºC), when less than 0.020 inch (0.51 mm) of metal is to
be removed from any surface, shall be controlled to prevent carburization or nitriding or to prevent total
decarburization.
3.1.1.4.2 Carbon and low-alloy steels heat treated to minimum tensile strength levels below 220 ksi (1517 MPa) shall
meet the surface contamination requirements of AMS2759/1. Steels heat treated to minimum tensile strength
levels of 220 ksi (1517 MPa) and higher shall meet the applicable surface contamination requirements of
AMS2759/2.
3.1.1.4.3 Furnaces equipped with integral oil quench tanks shall not be permitted for processing titanium and titanium
alloys above 1000 ºF (538 ºC), or for processing corrosion-resistant steels above 1100 ºF (593 ºC), unless
appropriate tests such as a surface contamination tests as in paragraph 3.1.1.4. are conducted to ensure no
detrimental surface effects are caused by such treatments.
3.1.1.4.4 Heat treated titanium and titanium alloy parts shall meet the applicable surface contamination requirements of
AMS2801. For heat treat loads containing small parts (e.g. fastener components) such parts may be
substituted for the coupons specified in paragraph 3.1.2.2.5.
3.1.1.4.5 Heat treated precipitation hardening corrosion resistant and maraging steels shall meet the applicable surface
contamination requirements of AMS2759/3. Austenitic corrosion resistant steels shall meet the applicable
surface contamination requirements of AMS2759/4. Martensitic corrosion-resistant steels shall meet the
applicable surface contamination requirements of AMS2759/5.
3.1.1.4.6 Surface contamination tests shall be carried out weekly unless the referenced standard requires more
frequent testing.
3.1.1.5 In addition to the tests specified in paragraphs 3.1.1.3 and 3.1.1.4, test for surface contamination on damage
tolerant or fracture critical parts shall be performed on each lot to the requirements stated in 3.1.1.4.1, 3.1.1.4.2,
3.1.1.4.3, 3.1.1.4.5 and 3.1.1.4.6. It is the responsibility of the purchaser to inform the heat treater on the
drawing, contract, or purchase order that parts are damage tolerant or fracture critical.

3.1.2 Pyrometry
Shall conform to AMS2750.
3.1.2.1 Working Thermocouples
Thermocouples shall be suitably protected and be of a type compatible with the range of temperatures and vacuum
conditions used. They shall be of a suitable size and located such that they receive direct radiation from the heating
elements and furnace walls.
3.1.2.1.1 The thermocouple types shown in Table 4 shall not be used unprotected (base wire, i.e., other than protective
sheathed) above the temperatures shown in Table 4.
3.1.2.1.2 Use of other thermocouple types shall be approved by the cognizant engineering organization.
TABLE 1 – RECOMMENDED VACUUM RANGE AS A FUNCTION OF PROCESSING

TEMPERATURE RANGE FOR VARIOUS PURE METALS AND ALLOYS
Processing Range Processing Range Operating Range
Material °F °C (Microns)(6)(7)(8)(9)
(10)
Carbon and Alloy Steels 1000 to 1800 538 to 982 1 to 200(1)
(10)
Corrosion-Resistant Steels
Ferritic (12 to 17% Cr) 1200 to 1650 649 to 899 1 to 200(1)
Martensitic 1200 to 2050 649 to 1121 1 to 200(1)(3)
Austenitic 1750 to 2050 954 to 1121 1 to 200(1)
Precipitation Hardening 850 to 2150 454 to 1177 1 to 200(1)(3)
(10)
Super Alloys
Nickel Alloys 1150 to 2275 621 to 1246 0.1 to 100(2)(3)
Cobalt Alloys 1350 to 2250 732 to 1232 0.1 to 100(2)(3)
Iron Alloys 1600 to 2150 871 to 1177 0.1 to 200(2)(3)
(10)
Tool Steels
Air Hardening 1470 to 1850 799 to 1010 0.1 to 200(1)
Cold Work 1470 to 1950 799 to 1066 0.1 to 200(1)
Hot Work 1470 to 1900 799 to 1038 0.1 to 200(1)
High Speed (M Series) 1470 to 2250 799 to 1232 0.1 to 200(1)
High Speed (T Series) 1550 to 2375 843 to 1302 0.1 to 200(1)
Refractory Metals Above 1600 Above 871
Molybdenum, Tungsten 0.01 to 0.1
Columbium (Niobium) 0.01 to 0.1(4)
Tantalum 0.01 to 0.1(4)
Titanium and Titanium Alloys 1300 and below 704 and below 0.1 to 100(2)(4)
Above 1300 Above 704 0.01 to 1(3)(4)
(5)
Copper Alloys Below 1000 Below 538 10 to 400
1000 to 2100 538 to 1149 100 to 400
Notes:
(1) For pressures higher than 100 microns, partial pressures of approved gases are required (See 3.2.1).
(2) For pressures higher than 20 microns, partial pressures of approved gases are required (See 3.2.1).
(3) Nitrogen not permitted as a partial pressure gas above 1400 °F (760 °C).
(4) Hydrogen not permitted as a partial pressure or quench gas.
(5) Alloys containing zinc - not recommended.
(6) For clarity, the single vacuum term “micron” is used. See 8.2.17 for relation to other values commonly used.
(7) If pressures outside the recommended ranges are used, tests shall be performed to demonstrate that no detrimental alloy
depletion/enrichment has occurred.
(8) The pressures specified apply to vacuum furnaces not equipped for atmosphere circulation.
(9) For furnaces equipped with atmosphere circulation, partial pressures higher than those indicated may be used at
temperatures below 1000 °F (538 °C).
(10) At temperatures 2100 °F (1149 °C) and below, minimum pressure may be 1/10 of the value shown.

TABLE 2 - VACUUM LEVEL VERSUS RECOMMENDED GAUGE

Vacuum Level Gauge
10-6 micron to 1 micron Hot filament ionization
10-4 micron to 10 microns Cold cathode ionization
1 micron to 103 microns (1 torr) Thermocouple or Pirani
TABLE 3 – MAXIMUM PERMISSIBLE LEAK RATE FOR PROCESSING OF VARIOUS METALS

Leak Rate
Material Microns/Hour
Carbon and Alloy Steels 50
Corrosion-Resistant Steels
Ferritic (12 to 17% Cr) 50
Martensitic 50
Austenitic 50
Precipitation Hardening 50
Superalloys
Nickel Alloys 20
Cobalt Alloys 20
Iron Alloys 20
Tool Steels
Air Hardening 50
Cold Work 50
Hot Work 50
High Speed (M Series) 50
High Speed (T Series) 50
Refractory Metals
Molybdenum, Tungsten 20
Columbium (Niobium) 5
Tantalum 5
Titanium and Titanium Alloys 10
Copper Alloys 50
TABLE 4 - BARE THERMOCOUPLE TYPES VERSUS MAXIMUM OPERATING TEMPERATURE

Maximum Maximum
Temperature Temperature
Type °F °C
K (Chromel-Alumel) (1)(2) 2200 1204
N (Nicrosil-Nisil)(1) 2200 1204
Nickel-Nickel/Molybdenum 2300 1260
S,R (Platinum-Platinum/Rhodium) 2600 1427
B (Platinum/Rhodium-Platinum/Rhodium) 3100 1704
Tungsten-Tungsten/Rhenium 4000 2204
Notes:
(1) Bare thermocouples shall be discarded or recalibrated after being exposed to five heat treat
cycles or accumulation of five hours service at or above 2100 °F (1149 °C), or ten heat treat
cycles or accumulation of 10 hours service at 2000 to 2100 °F (1093 to 1149 °C).
(2) Type K bare thermocouples exposed to vacuum are not recommended for use as control
thermocouples for continuous service at temperatures above 1800 °F (982 °C).
3.1.2.1.3 The recommendations of ASTM MNL 12 shall be considered with respect to usage of thermocouples.
3.1.2.1.4 When used in metal or other sheaths, care shall be taken to ensure that no chemical reaction between the
sheath and the thermocouple wire can occur.

3.1.3 Quenching
Furnaces used for quenching shall be equipped with cooling means sufficient for the material and process being
performed.
3.1.3.1 Vacuum Cooling
Where there is a requirement for slow cooling after annealing or normalizing, cooling performed under vacuum or partial
pressure using inert gas is permissible. Controlled cooling using a programmed heat input is permitted provided load
thermocouples are used to measure the actual load temperature during the cooling period.
3.1.3.2 Gas Quenching
When gas quenching is specified, it shall be accomplished by backfilling the furnace with a gas which has no detrimental
metallurgical effect on the material being processed or on the furnace equipment. The system and the pressure of the
backfill gas selected shall be capable of cooling the parts at a rate sufficient to meet the material property requirements
specified by the cognizant engineering organization. The use of hydrogen as a quenching gas must be approved by the
cognizant engineering organization (See 3.2.3).
3.1.3.3 Oil Quenching
Oil quenching shall be performed by transferring the parts from the heating chamber to a separate chamber which has
been backfilled with an inert gas, and immersing the parts in a circulating oil. The quenching chamber shall have a means
to minimize the amount of oil vapors generated during quenching from entering the heating chamber to an amount which
shall have no detrimental effect (carbon pickup) on the processed material. Quench oil shall be compatible with the
vacuum level used during initial evacuation and shall be capable of quenching the parts at a rate sufficient to meet
specified property requirements.
3.1.3.3.1 Furnaces equipped with integral oil quench tanks shall not be permitted for processing titanium and titanium
alloys above 1000 °F (538 °C), or for processing corrosion-resistant steels above 1100 °F (593 °C), unless
appropriate tests are conducted to ensure that no detrimental surface effects are caused by such treatments.
3.1.3.4 Bake-Out Cycle
If a furnace has been used for brazing with a brazing alloy which could detrimentally affect the parts to be heat treated,
the furnace shall be subjected to a bake-out (clean-up) cycle before being used for heat treatment. If freedom from
detrimental effects is not known from prior experience or data, the bake-out cycle shall not be omitted without
concurrence of the cognizant engineering organization. The bake-out cycle shall be carried out at not less than 50 °F (28
C) degrees above the maximum intended heat treatment temperature and the minimum achievable pressure of the
furnace for not less than 1 hour. A bake-out cycle is not required if the heat treatment cycle is an integral part of a brazing
operation.
3.2 Partial Pressure Atmospheres
3.2.1 To minimize metal loss by vaporization, pure metals and alloys which have high vapor pressures should be
processed at pressures shown in Table 1. The composition and dewpoint of the process gas upon delivery from
the supply source shall be in accordance with the applicable requirements of CGA G-10.1 (Grade L) for nitrogen,
CGA G-11.1 (Grade C) for argon, CGA G-9.1 (Grade L) for helium, and CGA G-5.3 (Grade B) for hydrogen as
follows:
Nitrogen: 99.998 % pure, oxygen 10 ppm max, dewpoint -89º F (-67°C) or lower.
Argon: 99.997% pure, oxygen 5 ppm max, dewpoint -76º F (-60°C) or lower.
Helium: 99.995% pure, oxygen 5 ppm max, dewpoint -72º F (-58°C) or lower.
Hydrogen: 99.95% pure, oxygen 10 ppm max, dewpoint -60º F (-51°C) or lower.

3.2.1.1 Analysis of the dewpoint at the location of replenishment is not required, however, the dew point of the gas
shall be - 60 ºF or lower as the gas enters the furnace and shall be verified at least quarterly and also when the
piping transmitting the gas is disturbed. In lieu of sampling the dew point at each furnace, the gas may be
sampled at the end of each leg of supply piping, at the furthest point from the supply. Each addition of gas to
the system shall have been analyzed for purity and accompanied by a certificate of composition which shall be
reviewed and approved for use by the organization. Records of the analysis and review shall be maintained as
quality records per the organization. The specified gases may be used to maintain a pressure above the vapor
pressure of the material being treated, provided the gas selected does not react with the materials being
processed, the furnace construction materials, or the work support fixtures.
3.2.2 Hydrogen, when used to maintain a partial pressure reducing atmosphere, shall only be used with the prior
approval of the cognizant engineering organization.
3.2.3 The use of hydrogen in a vacuum furnace may be hazardous. Refer to NFPA 86D for safe practices for use of
hydrogen in a vacuum furnace.
3.2.4 Diffusion pumps shall be isolated from the main vacuum chamber to prevent backstreaming at chamber
pressures above those recommended by the manufacturer of the furnace, pump, and/or pump oil [typically
100 microns (100 µm)].
3.3 Outgassing
If the pressure rises during the heat-up cycle to a level such that either the partial pressure control level is exceeded and
the inert gas used to maintain such pressure is no longer flowing, or the vacuum level needed to maintain diffusion pump
operation is exceeded, the furnace shall be held at a constant temperature until the pressure drops to the acceptable level
or other corrective action is taken. If the condition does not clear itself after 15 minutes or the third attempt to increase
temperature, the run shall be aborted and the furnace and load inspected after cooling, unless the cause is known.
3.4 Cleaning
Parts, fixtures, and materials charged into the heating chamber shall be free of contaminants which might evaporate and
react with the material being heat treated or the furnace components. Handling of cleaned parts and fixtures shall be such
as to prevent contamination prior to charging into the furnace.
3.5 Heat Treatment
Shall be performed in accordance with the applicable specification and as follows:
3.5.1 Vacuum Level
Should be as specified in Table 1 or as specified by the cognizant engineering organization.
3.5.2 Protective Coatings
May be used to prevent direct exposure of the part surfaces to the vacuum atmosphere provided they do not cause
detrimental effects to parts and/or furnace components. If coatings or plating are used, compensation for changes in part
emissivity shall be made in the heating time. Additional heating time shall be determined by preproduction testing. When
copper plating is used, pressure shall not be lower than 150 microns (150 µm) at temperatures above 1600 °F (871 °C).
3.5.3 Part Loading
Parts shall be loaded to promote uniform heating and, when quenching is required, to permit uniform circulation of the
quench medium.

3.5.4 Load Thermocouples
One or more load thermocouples shall be used with each load with the exception noted in 3.5.4.3. The load
thermocouple(s) shall be compatible with the material being processed or adequately sheathed to prevent reaction with
the parts. The thermocouple(s) shall be located in the portions of the load which are predicted to be the last to attain the
desired temperature. The thermocouple(s) may be attached to the outer surface of the parts. If a thermocouple is placed
in a hole to measure the core or interior of the part being processed, the thermocouple must make intimate contact with
the surface at the bottom of the hole. To avoid errors due to conduction along the length of the thermocouple, the
minimum depth of insertion of the thermocouple shall be at least ten times the diameter of the thermocouple.
3.5.4.1 In the event a thermocouple fails, the run need not be aborted as long as another thermocouple continues to
record the correct temperature.
3.5.4.2 Once a load has been qualified with load thermocouple(s), subsequent loads can be run without load
thermocouple(s) provided adequate records detailing the number of parts and distribution of parts in the first
qualified load are kept on file, and provided that subsequent loads have an equal or fewer number of identical
parts in the load, and the distribution of the parts is the same as the distribution in the first load.
3.5.4.3 When use of load thermocouple(s) is impracticable, such as with two or three chamber oil or gas quench
furnaces, tests shall be conducted to establish the correct heat-up time for the load.
3.5.4.3.1 The test shall incorporate load thermocouple(s) in the actual or simulated load to establish the correct heat up
time for a given batch of parts, as a forerunner to the production heat treatment cycle without load
thermocouple(s). This procedure does not require quenching of the test load from the heat treatment
temperature.
3.5.4.3.2 Once such loads have been qualified as in 3.5.4.3.1, subsequent loads may be processed without load
thermocouple(s) provided records detailing the number of parts and the load configuration are kept on file,
provided that subsequent loads have an equal or fewer number of identical parts in the load, and the
distribution of the parts is the same as that used in the qualification load.
3.5.4.4 Load thermocouples shall not be tack welded to parts without the approval of the cognizant engineering
organization.
3.5.5 Fixturing
Shall provide adequate handling and positioning of parts and materials to promote uniform heating and uniform circulation
of the quenching media.
3.5.5.1 Fixture Materials
Shall be of adequate strength to support the parts being treated, and shall not react with the material being treated. In
particular, fixture/material combinations which readily form eutectics, as indicated in Table 5, should be used with caution
to avoid possible melting.

TABLE 5 - EUTECTIC TEMPERATURES FOR BINARY COMBINATIONS

Binary Metal °F °C
Molybdenum/Nickel 2410 1321
Molybdenum/Platinum 3780 2082
Molybdenum/Carbon 4010 2210
Nickel/Carbon 2400 1316
Nickel/Tantalum 2410 1321
Nickel/Titanium 1730 943
Nickel/Iron 2620 1438
Notes:
(1) Carbon (Graphite) reacts with nickel alloys and corrosion-resistant steels to form
eutectics melting as low as 2060 °F (1127 °C).
(2) Solid solutions and compounds may be formed by molybdenum in direct contact with
alloys of nickel, chromium, and iron at temperatures as low as 2200 °F (1204 °C).
(3) Molybdenum forms continuous solid solutions with titanium and vanadium which
reduce the melting point of molybdenum in relation to the percentage of the added
element.
(4) Molybdenum forms solutions with platinum, rhodium, rhenium, and tungsten at
temperatures over 2000 °F (1649 °C). Care should be taken where these materials
may come in contact.
3.6 Surface Discoloration
Unless otherwise specified by the cognizant engineering organization, surface discoloration shall not be cause for
rejection.
4. QUALITY ASSURANCE PROVISIONS
4.1 Responsibility for Inspection
Unless otherwise specified by the cognizant quality assurance organization, the heat treatment processor shall be
responsible for performance of all tests and inspections specified herein. The processor may use his own facilities or any
commercial laboratory acceptable to the cognizant quality assurance organization.
4.1.1 The purchaser reserves the right to perform any surveillance, tests, or inspection of parts and to review heat
treatment records and results of processor’s tests and inspections to verify that the heat treatment conformed to
requirements of this specification.
4.2 Classification of Tests
4.2.1 Acceptance Tests
Not applicable.
4.2.2 Periodic Tests:
Vacuum gauge calibration (3.1.1.2), leak rate (3.1.1.3), pyrometry tests (3.1.2), and dew point (3.2.1) are periodic tests
and shall be performed at the frequency specified herein.
4.2.3 Preproduction Tests
Vacuum gauge calibration (3.1.1.2), leak rate (3.1.1.3), and pyrometry tests (3.1.2) are preproduction tests and shall be
performed prior to any production heat treating on each piece of equipment (furnace) to be used.

4.3 Approval of Heat Treat Processors
Shall be accomplished by the cognizant quality assurance organization and will normally be based on the following:
4.3.1 Approval of the heat treat processor’s process procedures and process control documents which shall be used to
meet the requirements of this specification.
4.3.2 Competence of heat treat processor’s personnel. Personnel performing or directing the performance of heat
treatment in accordance with this specification shall be approved in accordance with ARP1962 or other
established procedures.
4.4 Logs
A record (written or electronic storage media), traceable to temperature recording information (chart(s) or electronic
storage media) and to shop travelers or other documentation, shall be kept for each furnace and load. The information on
the combination of documents shall include: equipment identification, approved personnel’s identification, date; part
number or product identification, number of parts, alloy, lot identification, AMS2769 or other applicable specification,
actual thermal processing times and temperatures used. When applicable, atmosphere control parameters, quench delay,
quenchant type, polymer concentration and quenchant temperature shall also be recorded. The maximum thickness,
when process parameters are based on thickness, shall be recorded and shall be taken as the minimum dimension of the
heaviest section of the part. The log data shall be recorded in accordance with the heat treater’s documented procedures.
4.5 Records
Shall be available to purchaser for not less than 5 years after heat treatment. The records shall contain all data necessary
to verify conformance to the requirements of this specification.
4.6 Reports/Certification
The heat treating processor shall furnish, with each shipment of parts, a certified quality assurance report, traceable to the
heat treat control number(s), stating that the parts were processed in accordance with the requirements of AMS2769B (or
other applicable specification). The report shall include: purchase order number, part number or product identification,
alloy, temper/strength designation, quantity of parts in the shipment, identification of furnace(s) used, actual thermal
processing times and temperatures used. When applicable, the report shall also include: atmosphere type, quenchant
(including polymer concentration range), hot straightening temperature and method of straightening (e.g., press, fixtures),
actual test results, (e.g., hardness, conductivity, tensile, shear etc.) and a statement of their
conformance/nonconformance to requirements. This data shall be reported in accordance with the heat treater’s
documented procedures.
5. PREPARATION FOR DELIVERY:
5.1 Identification
Not applicable.
5.2 Packaging
5.2.1 Parts shall be packaged to ensure protection from damage during shipment and storage.
5.2.2 Packages of 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.
6. ACKNOWLEDGMENT:
The heat treatment processor shall mention this specification number and its revision letter in all quotations and when
acknowledging purchase orders.

7. REJECTIONS
Parts not heat treated in accordance with the requirements of this specification, or with modifications authorized by
purchaser, will be subject to rejection.
8. NOTES
8.1 A change bar (|) located in the left margin is for the convenience of the user in locating areas where technical
revisions, not editorial changes, have been made to the previous issue of this document. An (R) symbol to the left
of the document title indicates a complete revision of the document, including technical revisions. Change bars and
(R) are not used in original publications, nor in documents that contain editorial changes only.
8.2 Definitions of terms used in AMS are presented in ARP1917 and as follows. The following list defines various terms
commonly used in vacuum heat treating. These definitions are only presented to assist personnel not familiar with
vacuum heat treatment. Some of the terms listed may not appear in the main body of the specification.
8.2.1 Residual Gases
Those gases remaining after a furnace is evacuated to its initial vacuum level. In a typical furnace, analysis of the residual
atmosphere at a vacuum level of about 10-3 torr indicates that less than 0.1% of the original air remains. The residual
gases usually consist mainly of water vapor with the other vapors being primarily organic from the seals, vacuum greases,
and vacuum oils. The oxygen content, referenced to atmospheric pressure, is likely to be less than 1 ppm. If all of the
residual gas in the vacuum furnace was water vapor, then referenced to standard atmospheric pressure and temperature,
the water vapor content would be approximately 1.5 ppm or equivalent to a gas with a dewpoint of about -110 °F (-79 °C).
At a vacuum level of 1 × 10-4 torr, the equivalent dewpoint of gas is estimated to be on the order of -130 °F (-90 °C) or
less.
8.2.2 Roughing Pump
A positive displacement mechanical pump which may or may not be used in combination with a rotary lobe (Roots type)
blower.
8.2.3 Holding Pump
A small mechanical pump automatically valved to the foreline of the diffusion pump at all times when the main mechanical
pump(s) are serving elsewhere (roughing or partial pressure).
8.2.4 Pump Speed
A measure of a pump’s capability of handling gases. Expressed in volumetric units such as liters/second or cubic
feet/minute.
8.2.5 Throughput
A measure of a pump’s actual pumping capability at a given pressure. Expressed in pressure-volumetric units, such as
torr liters/second or micron cubic feet/minute.
8.2.6 Virtual Leak
A source of gas in a vacuum system that acts like a leak in that the gas is trapped in a tight crevice, blind bolt hole, porous
weld, etc and “leaks” out over a long period of time.
8.2.7 Real Leak
Any path through the wall of a vacuum chamber that allows a gas to pass through, however small the rate.

8.2.8 Outgassing
The evolution of gas(es) from the surfaces of a vacuum system and its content. Unless there is a known reason for
excessive outgassing, such as binders and other volatiles in stop-off or shielding material, excessive outgassing should
be taken as a sign of a potentially serious problem such as a water leak or foreign object left in the furnace.
8.2.9 Degassing
A technique of accelerating the outgassing, usually by the application of heat.
8.2.10 Leak Rate
A general indication of vacuum integrity of a system. The system is pumped into the high vacuum range, the pumping
system is closed off, and the pressure rise over a given time of the closed system is observed. The rise will be the result
of all sources of gas including outgassing of internal surfaces, virtual leaks, and any real leaks.
8.2.11 Backstreaming
A term used to describe the “upstream” motion of some oil vapor molecules, for example, for the top portions of a hot
diffusion pump. Normal motion of gases is from high pressure (the furnace) to low pressure (the pump). In backstreaming,
pump oil vapors move in the reverse direction, into the furnace.
8.2.12 Partial Pressure
The actual pressure of any single gas component of a vacuum atmosphere. The total pressure is the sum of all of the
partial pressures of the gaseous constituents of the atmosphere.
8.2.13 Vapor Pressure
The gas pressure exerted when a substance is in equilibrium with its own vapor. Vapor pressure is a function of
temperature as shown in Figure 2 for pure metals. Vapor pressure of an alloy can be considered to be governed by
Dalton’s law of partial pressures: The total vapor pressure of an alloy under ideal conditions is equal to the sum of the
partial pressures of its constituents. The partial pressure of each element in an alloy is roughly proportional to its
concentration. Vapor pressures of most oxides and compounds are lower than those of their pure elements, as shown in
Figure 2 for unalloyed metals and pure metals.
8.2.14 Residual gas analysis by mass spectrometer may be used to identify the specific gases in the system.
8.2.15 A helium mass spectrometer leak detector may be used to determine if leaks are present in the system.
8.2.16 Vaporization Rate
The rate at which a substance vaporizes or attempts to reach its equilibrium vapor pressure. The relationship to
temperature is shown in Figure 3.
8.2.17 Units of Pressure
Pressure in a vacuum furnace is expressed in absolute units, referenced to standard atmospheric pressure at sea level,
45 degrees latitude and 0 °C (32 °F). Vacuum furnace pressure is expressed in units of torr (mm of mercury) microns of
mercury, or millibar. Relative to one standard atmosphere, these units have the following values.
1 micron = 0.001 mm of mercury

= 1 × 10-3 Torr
1 atmosphere = 760 mm of mercury

= 1000 millibar

8.2.18 Ultimate Pressure
The lowest pressure reached in an empty, clean, degassed furnace after pumping for a reasonable length of time at
ambient temperature.
8.2.19 Cognizant
The term applied to the engineering organization responsible for the design of the part, its allied quality assurance
organizations, or a designee of these organizations.
8.3 NFPA 86D Standard
This standard contains recommended design and safe operating practices for vacuum furnaces. Additional useful
definitions and vacuum terminology are also included. NFPA 86D should be consulted whenever combustible or other
toxic gases are to be used as partial pressure gases in vacuum furnaces. This document should be referred to
concerning the use of components for vacuum furnaces.
8.4 Parts
Heat treatment of parts is any heat treatment not performed by or for a material producer. It is performed by a
fabricator/user, or his designee, to meet the requirements of a drawing. The requirements are usually conveyed by a
purchase order, fabrication outline, and/or a heat treating specification. Parts, at the time of heat treatment, may resemble
raw material.
8.4.1 Parts are usually identified by a part number and, except for those produced in large quantities (e.g., rivets), are
usually tested only by nondestructive techniques.
8.5 Notes to Figures
8.5.1 Figure 2
Temperature at which vapor pressure exceeds 0.01 micron (10-5 torr) for high temperature pure metals used or treated in
vacuum (See Table 6).
TABLE 6 - VAPORIZATION TEMPERATURES

Element °F °C
Cr 1944 1062
Zr 3340 1837
Pt 2913 1602
Rh 2890 1587
Mo 3613 1987
C 3595 1977
Ta 4350 2397
W 4620 2549

8.5.2 Figure 3
Temperature at which evaporation rate exceeds 10-6 g/cm2 seconds for high temperature pure metals used or treated in
vacuum (See Table 7).
TABLE 7 - EVAPORATION TEMPERATURES

Element °F °C
Cr 1796 980
Zr 2950 1621
Pt 3100 1704
Rh 3180 1749
Mo 3800 2093
C 4220 2327
Ta 4700 2593
W 4900 2704
8.5.3 Figures 1, 2, and 3
The data contained in these figures are provided for information purposes and should be used only as guides.
8.6 Terms used in AMS are clarified in ARP1917.
8.7 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.
PREPARED BY AMEC AND AMS COMMITTEE “F”

FIGURE 1 - APPLICABLE PRESSURE RANGES FOR VACUUM PUMPS (SEE 8.5.3)

FIGURE 2 - VAPOR PRESSURE OF THE ELEMENTS (SEE 8.5.1 AND 8.5.3)

FIGURE 2 - VAPOR PRESSURE OF THE ELEMENTS (SEE 8.5.1 AND 8.5.3) (CONTINUED)

FIGURE 3 - EVAPORATION RATE OF THE ELEMENTS (SEE 8.5.2 AND 8.5.3)

FIGURE 3 - EVAPORATION RATE OF THE ELEMENTS (SEE 8.5.2 AND 8.5.3) (CONTINUED)

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Heat Treatment of Parts in a Vacuum

1.3 Safety - Hazardous Materials

SAE INTERNATIONAL AMS2769B Page 2 of 19

2.1 SAE Publications

ARP1962 Training and Approval of Heat-Treating Personnel

2.2 ASTM Publications

ASTM MNL 12 Manual on the Use of Thermocouples in Temperature Measurement

2.3 National Fire Protection Association (NFPA)

NFPA 86D Standard for Industrial Furnaces Using Vacuum as an Atmosphere

2.4 CGA Publications

CGA G-5.3 Commodity Specification for Hydrogen

3.1 Furnace Equipment

3.1.1 Vacuum System

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SAE INTERNATIONAL AMS2769B Page 3 of 19

3.1.1.1 Vacuum Sensing Equipment

3.1.1.2 Vacuum Gauge Calibration

3.1.1.3 Leak Rate

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SAE INTERNATIONAL AMS2769B Page 4 of 19

Shall conform to AMS2750.

3.1.2.1 Working Thermocouples

TABLE 1 – RECOMMENDED VACUUM RANGE AS A FUNCTION OF PROCESSING

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SAE INTERNATIONAL AMS2769B Page 5 of 19

TABLE 2 - VACUUM LEVEL VERSUS RECOMMENDED GAUGE

TABLE 3 – MAXIMUM PERMISSIBLE LEAK RATE FOR PROCESSING OF VARIOUS METALS

TABLE 4 - BARE THERMOCOUPLE TYPES VERSUS MAXIMUM OPERATING TEMPERATURE

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SAE INTERNATIONAL AMS2769B Page 6 of 19

3.1.3.1 Vacuum Cooling

3.1.3.2 Gas Quenching

3.1.3.3 Oil Quenching

3.1.3.4 Bake-Out Cycle

3.2 Partial Pressure Atmospheres

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SAE INTERNATIONAL AMS2769B Page 7 of 19

3.5 Heat Treatment

Shall be performed in accordance with the applicable specification and as follows:

3.5.1 Vacuum Level

Should be as specified in Table 1 or as specified by the cognizant engineering organization.

3.5.2 Protective Coatings

3.5.3 Part Loading

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SAE INTERNATIONAL AMS2769B Page 8 of 19

3.5.4 Load Thermocouples

3.5.5.1 Fixture Materials

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SAE INTERNATIONAL AMS2769B Page 9 of 19

TABLE 5 - EUTECTIC TEMPERATURES FOR BINARY COMBINATIONS

3.6 Surface Discoloration

4. QUALITY ASSURANCE PROVISIONS

4.1 Responsibility for Inspection

4.2 Classification of Tests

4.2.1 Acceptance Tests

4.2.2 Periodic Tests:

4.2.3 Preproduction Tests

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