MIL-STD-867 Temper Etch InspectionThis standard establishes requirements and test for performing temper etch inspection of carburized steels and tool and low alloy steels, which are heat treated above 1.24 x 109 Pascal PA 1.26 x 102 kilogram - force/square millimeter Kgf/mm2 or 1.8 x 105 pound - force/square inch psi. This standard applies to aircraft and missiles structural and propulsion system components when MIL-HDBK-6870 for guidance only and/or MIL-STD-866 are reference documents in the solicitation or contract.

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MIL-STD-867C

5.6.3   Magnetic particle inspection.  All parts shall be magnetic particle inspected in accordance with ASTM - E1444 after baking and prior to other processing, which

might hinder detection of a discontinuity.

5.6.4   Records.   Historical records shall be maintained on all chemical tests and on additions made to the solution.

5.7   Re-etching.  A part may be etched two or more times, if dimensions and surface finishes allows, in order distinguishing burn indications from irrelevant indications; such as, smear or smutty finishes.  Aluminum oxide or garnet grit blast between re-etch is recommended.

5.8   Seeking competent advice.  A metallurgist shall be consulted in instances where the results of the etching appear inconclusive and where further interpretation is required.

5.9   Hardness testing.  If part size and configuration permits, hardness testing in accordance with ASTM - E18 using 15/N Rockwell test equipment may be used as an evaluation of hardness in moderate to heavy over-tempered areas.  A reduction of two (2) Rockwell 15/N points or more from the areas directly adjacent to the burn is

indicative of an over-stressed and crack susceptive condition and should not be accepted in high stress areas.  In lieu of Rockwell 15/N hardness testing, 1000 gram maximum load micro-hardness testing may be employed.

5.10   Rework/salvage.  If sufficient stock remains for rework within the specified dimensions, the parts may be reworked to remove indications of over-tempering or re- hardening.  Parts subjected to this rework shall be re-acid etch inspected.

5.11   Acid etch removal.  Discoloration from the acid etch inspection process shall be acceptable unless otherwise specified by the drawing or customer requirements. The discoloration may be removed by polishing, honing, vapor grit blasting, or

electrolytic alkaline cleaning methods providing dimensional changes do not exceed drawing requirements and customer approval is obtained.

5.12   Marking.   Parts which have met the etch inspection requirements shall be marked in accordance with the applicable drawing, specification, purchase order or contract.  Marking, as specified, shall be applied in such manner and location as to be harmless to the part and which will preclude removal, smearing, or obliterating by subsequent handling.  A symbol N, NE or AE may be used.  Provision shall be made to identify the individual inspector accomplishing the temper etch inspection along with the date and time the inspection was performed.  In lieu of marking the part and as allowed by contract, an approved process control document (traveler, work control document, etc.) that identifies the specific part by part number and serial number may be annotated.

5.13   Toxic and hazardous substances.  This document specifies use of certain materials which have been listed in subpart Z, 29 CFR 1910 (OSHA Standards), "Toxic and Hazardous Substances."  Personnel exposure to these materials must be limited to the values specified in applicable portions of 29 CFR 1910.1000.

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