Stainless Steel Fabrication and Machining Sources in Lafayette, IN

Subaru's Lafayette plant produces vehicles with full exhaust after-treatment systems — catalytic converters, particulate filters, and resonators — that require precision-stamped and TIG-welded stainless components. Grade 304 (18% Cr, 8% Ni) is the workhorse here: formable enough for deep-drawn exhaust cones and flanges, and resistant to the high-temperature oxidation seen in exhaust streams up to 1,500 degrees F. Local stamping houses run 304 in 0.048-inch to 0.120-inch gauge for these applications, forming to bend radii as tight as 1T on simple geometries. For higher-temperature zones near the turbocharger or catalytic brick, suppliers step up to 321 or 409 stainless, though the broad commercial production in Lafayette centers on 304. Orbital tube welding is used for exhaust tube assemblies requiring consistent bead geometry and leak-free joints rated to 150 psi back-pressure; Lafayette's automotive welding shops have the fixtures and automated orbital heads to produce thousands of these assemblies per shift. Beyond exhaust, 304 stainless appears in fuel system brackets, EGR cooler housings, and sensor bungs throughout the powertrain. Surface finish requirements on these parts range from a mill finish (2B) for non-visible brackets to a 180-grit polish on any surface contacting fuel or coolant to minimize contamination risk.

Caterpillar's Lafayette operations produce equipment that operates in environments where hydraulic systems are exposed to water, fertilizers, road salts, and agricultural chemicals — all of which would rapidly corrode carbon steel fittings and manifolds. Grade 316L (2-3% Mo, 0.03% max carbon) is the specified material for hydraulic fittings, manifold blocks, and sensor housings on equipment lines where chloride exposure is a design constraint. The low-carbon 'L' designation matters here: when shops TIG weld 316L components without post-weld annealing — which is common in production environments — the lower carbon content prevents sensitization and intergranular corrosion at the heat-affected zone. Lafayette fabricators who supply Caterpillar work understand this distinction and will not substitute standard 316 without engineering sign-off. Manifold blocks machined from 316L bar stock require sharp tooling, rigid fixturing, and slower feed rates than 304 due to 316L's higher work-hardening rate — most shops run 30-40% lower surface footage than they would on 304. Passivation per ASTM A967 is standard post-machining treatment for hydraulic stainless parts in this market. The nitric acid or citric acid bath removes free iron from the surface and restores the chromium oxide passive layer, which is critical for components that will sit in inventory for months before assembly. Lafayette shops either passivate in-house or use a dedicated Indianapolis finishing house with certified chemical baths and documented process control.

When Lafayette suppliers need stainless strength beyond what 304 or 316L can deliver — yield strengths above 100 ksi — 17-4PH precipitation-hardened stainless becomes the material of choice. In the H900 condition, 17-4PH achieves 170 ksi yield, which is territory approaching alloy steel without sacrificing corrosion resistance. Caterpillar-adjacent suppliers use 17-4PH for high-cycle fasteners, shafts, and structural pins on equipment exposed to both high mechanical loads and corrosive environments. Machining 17-4PH requires careful grade-state planning. Many shops receive 17-4 in the annealed (A condition) state, machine to near-net shape, then send to heat treater for H900 or H1025 aging — which adds dimensional change of 0.0005-0.001 inch per inch that must be accounted for in the machining allowance. H1025 (aged at 1,025 degrees F) provides a better balance of toughness and strength than H900 and is increasingly preferred for heavy-equipment parts where impact loads are a factor. Duplex 2205 (22% Cr, 5% Ni, 3% Mo) appears in demanding structural and pressure-vessel applications where both high strength (65 ksi yield minimum) and chloride stress-corrosion resistance are required. Its mixed austenitic-ferritic microstructure gives it roughly twice the yield of 316L and dramatically better resistance to pitting and crevice corrosion. Lafayette suppliers who work with Duplex 2205 note that it requires specialized cutting parameters — lower speeds, higher feeds, and positive-rake geometry — to avoid rapid work hardening that dulls tooling prematurely.

TIG welding is the primary joining process for stainless fabrications in Lafayette's industrial shops. Automotive exhaust assemblies, hydraulic manifolds, and structural frames all require full-penetration welds with controlled heat input to minimize distortion and HAZ sensitization. Shops use back-purging with argon for tube assemblies and orbital welding for high-volume exhaust tube production. Filler metal selection follows AWS D1.6 (structural stainless) or automotive OEM weld specifications; ER308L is standard for 304 base metal, ER316L for 316L base. Laser welding is available at several Lafayette-area shops for thin-gauge stainless assemblies where heat input must be minimized. Fiber laser systems running 3-6 kW can produce cosmetic welds on 0.030-0.060 inch gauge 304 without the distortion seen with conventional TIG — useful for sensor housings and instrumentation brackets on precision equipment. For surface finishing, electro-polishing is available regionally and is specified for food-adjacent equipment and medical-grade stainless components. Bead blasting (glass bead, 120-220 grit) is used to produce a uniform matte finish on fabricated assemblies. Electropolished 316L achieves Ra 16 or better, which is the surface finish baseline for pharmaceutical and food processing components made in this area.