What Is HIP
Hot Isostatic Pressing (HIP) subjects components to simultaneous high temperature and high isostatic gas pressure (typically argon at 15,000–30,000 PSI) in a specialized pressure vessel. Under these conditions, internal porosity and microporosity in castings collapse and diffusion bond shut, producing a fully dense material with mechanical properties approaching wrought equivalents. HIP is considered mandatory for safety-critical superalloy castings in aerospace, nuclear, and high-integrity industrial applications because it eliminates the internal voids that act as fatigue crack initiation sites.
HIP Benefits for Castings
HIP processing improves superalloy casting properties in several ways. Fatigue life increases by 2 to 10 times compared to un-HIPed castings because the porosity that initiates fatigue cracks is eliminated. Ductility and impact toughness improve as the volume fraction of void space approaches zero. Mechanical property scatter decreases because all castings achieve similar density levels, providing more predictable performance. And X-ray rejection rates decrease because sub-surface porosity that would cause radiographic rejections is eliminated before inspection. CastAlloy includes HIP as a standard step in our casting production sequence for all safety-critical applications.
HIP Parameters
HIP parameters vary by alloy. Inconel 718 castings are typically HIPed at 2,165°F and 15,000 PSI for 4 hours. Inconel 625 is processed at 2,125°F and 15,000 PSI. Titanium alloys require lower temperatures (1,650–1,750°F) to avoid phase transformation. Our metallurgical team selects the optimal HIP parameters for each alloy and specification combination. Contact us for HIP processing of your superalloy castings.