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T he Orion Multipurpose Crew Ve- hicle is NASA’s vehicle for hu- man exploration of deep space. Its maiden voyage—Exploration Flight Test 1—was an unmanned flight de- signed to test the vehicle’s main sys- tems, which launched from Kennedy Space Center on December 5, 2014. The trip included two earth orbits followed by reentry at approximately 20,000mph, subjecting the heat shield to 4000°F. Landing and recovery took place in the Pacific Ocean. Among the technology advancements included on Orion were additively manufactured (AM) vents used as air passages for the unpressur- ized portions of the spacecraft. Exploration Flight Test 1 used four vent assemblies to equalize pressure between the unpressurized portions of the spacecraft and the external environ- ment. The assemblies contained the AM housings and integral screens as well as two additional screens that were weld- ed on. Each assembly was then bolted into the vehicle using three mounting flanges. Complete assemblies were roughly the size of a 1-liter water bottle. Initial design called for a wire mesh to be welded into the housing. Multiple screens were needed for re- dundancy, and a cylindrical shape was desired due to space limitations inside the vehicle. Because this initial design proved difficult to produce, additive Parts were additively manufac- tured from a nickel alloy (Inconel 718) using the vendor’s recommended pro- cedure. (Note that this was before in- dustry specification ASTM F3055 was available for use.) Each build cycle con- tained one part and corresponding test coupons. Parts were additively manu- factured, stress relieved, hot isostati- cally pressed (HIP’d), solution treated, and aged. This corresponds with ASTM F3055, Class D, although the processing parameters were not identical. Machin- ing was performed on some surfaces to remove the support structure or to provide a smooth surface for fastener installation. Welding was performed using industry specification AWS D17.1. manufacturing was proposed. PARTS MANUFACTURING

A D V A N C E D M A T E R I A L S & P R O C E S S E S | J A N U A R Y 2 0 1 6

Fig. 1 — Complete passive vent assembly. The mesh on the top was welded onto the additively manufactured housing.

Fig. 2 — Close-up of passive vent, showing AM screen details.

Development welds were performed and examined to determine sufficiency of the weld schedules. DEVELOPMENT TESTING Three witness coupons were print- ed with each part, comprising tensile specimens in the x, y, and z orientations (where x and y are on the build plane and z is in the build direction). Speci- mens were manufactured as cylinders, machined to a 0.25-in. test diameter, and tested per ASTM E8 at room tem- perature. All specimens met ASTM F3055 Class D requirements and were within 15% of specification values. Fig- ure 3 shows typical specimens. Three tensile specimens were in- tentionally not HIP’d for comparison. These non-HIP’d specimens exhibited approximately the same strength as the HIP’d specimens, suggesting that the HIP process may not provide a signifi- cant strength benefit.

Fig. 3 — Representative tensile specimens after testing.

Microstructural evaluations were also performed. Overall, specimens ex- hibited very little porosity. Grains were finer near the edges than in the center of the coupons. Specimens were free of Laves phase, an undesirable interglob- ular phase [1,2] . A typical microstructure is shown in Fig. 4 (50 × magnification).