Operating a hot isostatic press? The stages for HIP processing can become faster and more effective with gas detection technology. Learn about real-time leak detection analysis and continuous monitoring for outgassing.
This Technical Tuesday article by Erik Cox, manager of New Business Development at Gencoa, was originally published in Heat Treat Today’s March/April 2024 Aerospace print edition.
The Problem in HIP
Hot isostatic pressing (HIP) is a widely employed method for densifying powders or cast and sintered parts. It involves subjecting materials to extreme conditions — high pressure (100–200 MPa) and high temperature (typically 1652°F–2282°F, or 900–1250°C) — in a specialized vessel.
One aspect of HIP comes before introducing metal or ceramic powders to the vessel: Operators must test for any leaks in the canisters. This ensures that the proper HIP processing can be completed. Secondly, outgassing of the powder must be performed, and thirdly, outgassing the HIP chamber should be done. All three are essential steps that are typically time consuming and inefficient, but new gas detection technology can make this pre-processing stage faster and more effective.
Real-Time Analysis for Leak Detection
Leak detection is normally performed with a helium leak detector, which are expensive and require significant technical knowledge to operate. Some HIP processing providers simply forego leak checking of the canister, fill the HIP canister with powder, and perform the degas; but in this case, any leaks will be identified during the degas process, and powder must then be removed to repair the canister.
HIP users must look to technology that effectively detects leaks before they proceed to outgassing. One example of this is Gencoa’s Optix gas sensor: As the pumping procedure commences and pressure reaches 0.5 mbar (which typically occurs within 15–30 seconds), the device switches on and employs a sophisticated analysis of the nitrogen that enters the canister from the atmosphere to discern the leak rate of the canisters. When a leak is detected, argon gas can be sprayed around the canister to accurately detect the leak point and allow repair.
Outgassing: Traditional vs. Continuous Monitoring
Outgassing is a critical step in the preconditioning of powders for HIP processed components, involving the removal of adsorbed gases and water vapor from the metal powder through vacuum pumping. Traditionally, the endpoint for this process is not monitored, leading to an overly long vacuum pumping stage of up to several days to ensure that the powders are correctly prepared.
Th is challenge is addressed by providing continuous monitoring throughout the entire degassing process, reducing the time to degas through the ability of the Gencoa Optix gas sensor to precisely determine the degas endpoint.
By offering real-time feedback and notifying users when degassing is complete, this sensor saves time and ensures the production of high-quality components with traceability. With the Optix, one user saw their degas times reduced from 24 hours to 4 hours. The sensor is capable of residual gas analysis, providing a comprehensive solution for improved productivity. Its wide-range pressure measurement capabilities, coupled with efficient leak checking of HIP processing enclosures, further enhance the overall operational efficiency.
Optix operates as a highly sensitive, stand-alone device that utilizes a small plasma (“light”) that detects the gas species present. This design ensures that the detector remains impervious to contamination or vacuum issues, maintaining continuous monitoring and avoiding potential damage. Because the device also eliminates the need for filament replacement or disassembly of components for maintenance, the design will perform at 100% operational uptime even in the harshest environments.
Indispensable Tools for HIP Processing
HIP operators need to maintain equipment efficiently and effectively, and technologies that integrate solutions not only enhance overall productivity, leak detection, and control of the degassing process, but are indispensable to improving the overall quality and traceability of components. Leveraging technologies that allow for early detection and increase uptime will only enhance the future HIP can offer to the AM-focused aerospace industry.
About the Author
Dr. Erik Cox is a former research scientist with experience working in the U.S., Singapore, and Europe. Erik has a master’s degree in physics and a PhD from the University of Liverpool. As the manager of New Business Development at Gencoa, Erik plays a key role in identifying industry sectors outside of Gencoa’s traditional markets that can benefit from the company’s comprehensive portfolio of products and know-how.
For more information:
Contact Erik at sales@gencoa.com
