nadcap ac7101-5 rev c

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AUDIT CRITERIA

AC 7101/5 REV. C

Issued 1993-05 Revised 2011-05 Superseding AC7101/5 Rev. B

TO BE USED ON AUDITS CONDUCTED ON OR AFTER AUGUST 28, 2011 Nadcap

AUDIT CRITERIA FOR MATERIALS TESTING LABORATORIES – HARDNESS TESTING (MACRO)

1.0 SCOPE This checklist supplements PRI AC7101/1. This checklist applies to suppliers seeking Nadcap

accreditation for Materials Testing Laboratories – Hardness Testing (Macro). 2.0 GENERAL INFORMATION 2.1 Laboratory 2.2 Laboratory Contact 2.3 Auditor 2.4 Initial Accreditation Re-accreditation Follow-up NOTE: The Bold sections in this document represent the interpretations for each section of this checklist. Items

noted with a single asterisk (*) are additional Nadcap requirements. NOTE: Applicable definitions can be found inAC7101/1 General Requirements for Laboratories.

2.5 Tests Audited:

TEST CODE CHECKLIST

TEST TYPE EQUIVALENT TEST METHODS

M1 AC7101/5 Hardness HB ASTM E10 ISO 6506 EN ISO 6506

M2 AC7101/5 Hardness HR ASTM E18 ISO 6508 EN ISO 6508

M3 AC7101/5 Hardness HV ASTM E92 ISO 6507 EN ISO 6507

PRI AC 7101/5 Revision C - 2 -

2.6 *External Proficiency Testing (PT) and Internal Round Robin (RR) Programs:

TEST TYPE NONE INTERNAL RR EXTERNAL PT

Brinell Hardness (HB)

Rockwell Hardness (HR)

Vickers Hardness (HV)

Other (List)

Reference Appendix B per AC7101/1 for the requirements relative to External

Proficiency and Internal Round Robin Testing.

2.7 The laboratory shall maintain an equipment inventory list used for acceptance testing

of material with the following information: YES NO

a. Laboratory Name b. Testing Equipment

Hardness Type Location (lab or shop) Digital, Analog (Dial) or Brinell scope Scales or Brinell loads used Equipment Calibration Frequency

c. Indenter Type(s) Inspection Frequency

3.0 PROCEDURES AND DOCUMENTS 3.1 Written instructions shall cover the following testing variables:

a. Number of impressions for each test value reported. YES NO Refer to section 10.5 for indentation spacing requirements.

b. Reading techniques for non-digital readout testing. YES NO *Reading techniques for non-digital readout testing (e.g. parallax considerations in reading Rockwell dials).

c. Daily verification process and recording of results. YES NO

d. Preclude the use of correction factors to compensate for machine error. YES NO 3.2 Written procedures cover operator options for hardness re-test. (Some operator

discretion is permitted) YES NO

Hardness Re-Test: Because problems such as specimen wobbling may occur which are apparent only to the operator and only at the time of testing, operators may choose to disregard test impressions they suspect of being irregular. Provided two additional impressions are made, both of which give conforming values and whose variations are typical for the material and hardness procedure, the suspect test may be disregarded and need not be recorded in the log or on the certificate.


3.3 Written procedures cover hardness referee test. (May be checked against applicable

standard test methods.) YES NO

The laboratory shall have a procedure addressing Hardness Referee tests, which includes at least one of the following: a. Re-preparation of the specimen to improve surface finish, parallelism, and/or flatness. b. When “alternate” test methods are permitted, use of a hardness method or scale that best represents the

material being tested: for example. • Use of spherical indenter methods when material is work-hardenable. • Use of Brinell hardness on castings or other large-grain material. • Use of Brinell hardness when “Brinell or alternate” is specified. • Selection of load which produces maximum sensitivity of readings (higher loads for higher

hardnesses). c. Use of direct-reading digital equipment instead of equipment requiring human interpretation of readings. d. Make three or five impressions. All readings should conform to specification; report at least the median

value. NOTE: Median is used because it is an actual test reading. 4.0 PERSONNEL AND TRAINING 4.1 Verify personnel training for one testing discipline.

Function:

Equipment operated: 4.2 Training is documented. YES NO 4.3 Required training is referenced via the Quality Manual. YES NO 4.4 Training includes testing of irregular shapes, soft materials, and any special

applications. YES NO

4.5 Operators who read test machine dials or microscopically measure indentations shall

be evaluated against other operators for consistency. YES NO

5.0 FACILITIES AND EQUIPMENT 5.1 Hardness equipment is capable of performing the tests in accordance with all

applicable requirements. YES NO

Hardness testing equipment shall be designed to ensure that the force of the indenter is applied smoothly, and without impact (overload) forces being applied. The base of the equipment shall be constructed such that it is sufficiently rigid to react to the test load, with no rocking or lateral movement of the specimen. For Brinell hardness testing, the system utilized shall dampen acceleration of the load as it approaches the intended level. 5.2 The supplier has a written preventive maintenance plan in place. YES NO 5.3 The preventive maintenance plan is followed and logged. YES NO Review plan and log for preventive maintenance.


6.0 CALIBRATION 6.1 Calibration records are available. YES NO 6.2 Records show calibration is traceable to national standards (NIST, UKAS, etc). YES NO 6.3 The calibration is performed in accordance with all applicable requirements. YES NO 6.4 A review of the calibration certificates by the QA function or the defined technical

representative has been performed and documented. YES NO

6.5 All indenters shall be serialized. When it is not practical to mark the serial number on

the indenter due to size limitations, the serial number shall be marked on the container. (Rockwell only)

YES NO

Indenters consist of: 1, Ball indenters which frequently consist of a holder, a cap and a ball. A ball indenter holder shall have a serial number. 2, Diamond indenters. A diamond indenter shall have a serial number. 7.0 MATERIAL IDENTIFICATION AND CONTROL 7.1 Using general questions from PRI AC7101/1, verify through specific jobs in process

that this area complies. YES NO

A unique set of identifying numbers shall be assigned to each test, to ensure traceability from the certificate issued to the customer order, material tested, test methods used, test results and original cutting plan. The laboratory’s systems shall provide for tracking and accountability of all specimens. Specimens shall be stamped, tagged or otherwise identified to avoid inter-mixing, and shall remain identifiable until disposal. 8.0 ALTERNATE METHODS, HARDNESS CONVERSIONS 8.1 Alternative methods are used only if permitted by one of the following (Check all

applicable items below): YES NO

Material specification

Other as described below:

8.2 Hardness conversions are performed to: YES NO

ASTM E 140

ISO 18265

Other documents (describe below):

8.3 A conversion chart is used if one of the following conditions exist: YES NO

Alloy groups not covered by ASTM E 140

Work-hardenable materials (these may be noted if Rockwell hardness testing shows needle movement more than 2 seconds after the loading lever has stopped moving, or if ASTM E 140 conversion values do not hold true when load is changed for the same indenter).


Castings and other coarse grained material (in general, indentations should include

several grains) using microhardness in lieu of Rockwell or Brinell, or vice versa.

Alternate hardness methods, as described below

Describe:

8.4 When conversion is used, the inspection records show the measured values as well

as the converted values (i.e. conversion from another hardness scale or from tensile test).

YES NO

Prior to use of ASTM E140 or other conversions, a conversion report is required (primary versus equivalent method) for the following:

• Alloy groups not covered by ASTM E140. • Work-hardenable materials. • Castings and other coarse-grain materials. • Microhardness in lieu of Rockwell or Brinell; or vice versa.

Alternate hardness methods incorporating automatic test machines shall validate software performing hardness conversions to ensure adherence to ASTM E140. 9.0 CERTIFICATE OF TEST / CONFORMANCE 9.1 Test reports shall include all information required by the applicable industry

standard/material specification and customer specification/requirements. YES NO

For Brinell only when using a Type A measuring device a statement must be included on the test certificate to the effect that a Type A measuring device was used. 9.2 If conditions are other than normal operating conditions (ball diameter/load/load

time/etc.), those conditions are reported as required. YES NO

10.0 HARDNESS VERIFICATION The Auditor is to check several standard test blocks. 10.1 Prior to verification, the operator checks the anvil/fixture to ensure the absence of

damage or foreign material. YES NO

10.2 Standard blocks are available for the scales and loads that are to be used for testing. YES NO Hardness block identification shall consist of the following:

• An official mark on the test surface or the thickness to an accuracy of ±0.005 inches (0.1 mm), to verify the original surface has not been ground. The surface shall be uniformly polished, and free from scratches that may affect current indentation.

• Each block shall be marked with the serial number traceable to its certification, the mean hardness value, tolerance (if given) and the supplier’s identification.

10.2.1 Standard blocks appear to be in a condition suggesting acceptable verification,

including:

10.2.1.1 Surfaces are not re-ground/re-polished. YES NO 10.2.1.2 Indentations are only on the allowable test surface. YES NO


10.2.1.3 At least one test block shall be used, and when commercially available, the hardness

range of the test block shall be chosen to be within 15 Rockwell points of the hardness value that the testing machine is expected to measure. (Rockwell only)

YES NO

10.3 The hardness tester is periodically checked against standard test block(s) at the

following minimum frequencies:

10.3.1 *Once each working shift during which acceptance testing will be performed. YES NO 10.3.2 * When load, anvil, or indenter are changed (Prior to each test run, defined as testing

of materials using the same equipment set-up while the machine is under the control of the same operator).

YES NO

Whenever the load, anvil or indenter is changed, and before the machine is checked with a test block, the technician shall visually inspect the anvil and indenter. Preliminary indentations (may be on scrap stock) shall be made to ensure seating of the anvil and indenter.

• Brinell and Vickers: 1 indentation minimum • Rockwell: 2 indentations minimum

The Operator shall inspect the equipment prior to the periodic check, to ensure that there is no damage. This inspection shall include anvil and indenter. Frequency: Check once each working shift during which the tester will be used. 10.4 Hardness tester periodic checks are recorded and the test block identified. YES NO Periodic checks shall consist of at least two indentations for Brinell and Rockwell and five indentations for Vickers. All individual test block readings must be within +/- tolerance of the standard test block. Averaging of the reading is not to be used as acceptance criteria for the daily verification process. 10.5 Indentations are spaced (center to center, center to edge of block, etc.) at acceptable

distances per the given test method, unless marked to disregard. YES NO

METHOD CENTER TO

CENTER CENTER TO EDGE

Brinell 3 2½ Rockwell 3 2½ Vickers 2½ 2½

NOTE: Diameters for Brinell and Rockwell. Diagonals for Vickers. 11.0 BRINELL HARDNESS TESTING N/A 11.1 Brinell Equipment Periodic Checks 11.1.1 Periodic checks have been performed to the loads that have been used. YES NO 11.2 Brinell Set-Up Periodic Check (Before Acceptance Testing of Material) 11.2.1 The periodic verification records are current and complete. YES NO See guidance in section 10.4. 11.3 Specimens for Brinell Testing


11.3.1 The thickness of the specimen tested is such that no bulge or other marking shows

the effects of the test force on the side opposite the indentation. (As a general rule, the thickness should be at least 10 times the depth of the indentation).

YES NO

11.3.2 When indentations are made on a curved surface, the minimum radius of curvature of

the surface shall be two and a half times the diameter of the indenter ball. YES NO

11.3.3 The angle between the indenter force line and the surface of the specimen is a right

ange / perpendicular. (To verify compliance, the difference between the smallest and largest diameter readings of the same indentation shall be less than 0.1mm (0.004”).

YES NO

11.4 Brinell Test Cycle (For one indentation) 11.4.1 Selection of the load and indenter ball diameter is determined using the applicable

standard in order to produce an indentation diameter in the range of 24 to 60% of the ball diameter.

YES NO

11.4.2 The major load is applied steadily, without a jerk. YES NO 11.4.3 Load is applied for a time of 10 to 15 s unless otherwise required by the product

specification. YES NO

11.4.3.1 If test conditions are different than a 10 mm indenter, 3000 kgf scale and 10s to 15s

dwell time, the indenter diameter, test force, and dwell time are reported. YES NO

11.5 Brinell Hardness Readings 11.5.1 For each indentation two readings shall be taken 90 degrees apart around the

diameter of the indentation and the mean is used to calculate hardness. (NOTE: Automated test machines may convert from indentation depth.)

YES NO

12.0 ROCKWELL HARDNESS TESTING N/A 12.1 Rockwell Equipment Periodic Checks and Calibrations 12.1.1 The hardness test blocks being used are appropriate for the materials being tested.

(see 10.2.1.3) YES NO

12.1.2 When the operator reads an analog dial, operator training ensures that parallax (line

of site) error is not introduced. YES NO

12.1.3 Internal procedures address items 12.1.1 through 12.1.2 above. YES NO 12.1.4 The periodic verification records are current and complete. YES NO 12.2 Manual Control (if applicable) 12.2.1 The Minor Load is applied smoothly to reach +/-5 divisions of the “SET” position

before re-setting the dial to zero. YES NO

12.2.2 The Major Load is removed as defined in the applicable testing specification. YES NO 12.2.3 If times greater than stated in the application testing specification are used, those

times are specified in the product specification. YES NO

12.2.4 Any dwell time greater than that required by the applicable testing specification shall

be recorded and reported after the test results. YES NO


12.3 Hardness Readings 12.3.1 Non-Optimum specimens, such as large parts which require special fixtures or parts

of irregular geometry, may be used only for tests which require minimum limits only. YES NO

*A minimum of two indentations shall be made and compared for consistency to insure that the specimen did not move. 13.0 VICKERS HARDNESS TESTING N/A 13.1 Vickers Equipment Periodic Check 13.1.1 At least five hardness readings have been made on a standard test block on the scale

and at the hardness level at which the machine will be used. YES NO

13.2 Specimens for Vickers Testing 13.2.1 The surface of the specimen is sufficiently smooth enough to permit the reading of the

indentation diagonal to 0.0005 mm (0.00002”). YES NO

For Vickers, the accuracy to measure the diagonals shall be within ±0.0005 mm or ±0.5%, whichever is larger. 13.2.2 Corrections for radii of curvature (spheres, cylinders) are made in accordance with

the applicable standard. YES NO

13.2.3 The periodic verification records are current and complete. YES NO 13.3 Vickers Test Cycle for One Indentation 13.3.1 Magnitude of test is from 1 to 120 kgf. YES NO 13.3.2 Magnitude of test load is reported. YES NO

13.3.3 Test load is applied and removed smoothly. Load is applied for a time of 10 to 15

seconds, unless otherwise required by the product specification. YES NO

13.3.4 Time used is reported if other than 10 to 15 seconds. YES NO 13.4 Vickers Hardness Readings 13.4.1 For each indentation, two diagonals at 90° are measured and the mean used to

calculate hardness. YES NO


EXPLANATION SHEET

PARA NO.

COMMENT

nadcap ac7101-5 rev c

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