Hot isostatic pressing (HIP)

The HIP process, which subjects a component to elevated temperatures and pressures to eliminate internal micro-shrinkage, helped engineers respond to the aerospace industry’s increasingly stringent regulations.

HIP enabled engineers to design components so they could meet specifications for use in critical, highly stressed applications.

The HIP’ing Process

The HIP process provides a method for producing components from diverse powdered materials, including metals and ceramics.

During the manufacturing process, a powder mixture of several elements is placed in a container, typically a steel can.

The container is subjected to elevated temperature and a very high vacuum to remove air and moisture from the powder.

The container is then sealed and HIP’ed The application of high inert gas pressures and elevated temperatures results in the removal of internal voids and creates a strong metallurgical bond throughout the material.

The result is a clean homogeneous material with a uniformly fine grain size and a near 100% density.

Advantages of HIP’ed Materials

The reduced porosity of HIP’ed materials enables improved mechanical properties and increased workability.

The HIP process eliminates internal voids and creates clean, firm bonds and fine, uniform micro-structures.

These characteristics are not possible with welding or casting. The virtual elimination of internal voids enhances part performance and improves fatigue strength.

The process also results in significantly improved non-destructive examination ratings.

HIP and Maching

One of the primary advantages of the HIP process is its ability to create near-net shapes that require little machining. Conventional manufacturing methods use only 10-30% of the material purchased in the final product the rest is removed during machining. A HIP’ed near-net shape part typically uses 80-90% of the purchased material. As a result, machining time and costs are significantly reduced.

The strong combination of improved raw material use and greater machining efficiency that results from the HIP process has driven the growth of HIP’ed powder metal parts manufactured from nickel-based and titanium alloys.

In fact, HIP has become the standard ‘bill of material’ on virtually all powder metal components produced by Howmet’s HIP operation.

What Type of Things can be Produced by HIP’ing?

The HIP process enables engineers to produce materials of all shapes and sizes, including cylindrical billets, flat rectangular bar billets, solid shapes with complex external geometry, and complex shapes with internal cavities.

Because powder metals do not have the directional property characteristics of forgings, the HIP process can produce materials from metallic compositions that are difficult or impossible to forge or cast. Howmet’s expertise in HIP powder compaction is displayed in the manufacture of abrasive tips, figure 1. Abrasive tips are uniquely layered compacts of ceramic and metallic powders which are used for turbine blade wear protection.
What HIP’ing can be used for

The HIP process is now not only used for densifying castings, but in many other applications such as diffusion bonding of dissimilar materials, component repair and powder metal consolidation. In the powder metal market, How met applies HIP technology in four separate areas:
• Consolidation of powder metals (PM)
• Creation of PM shapes
• Production of near-net shapes
• Cladding.

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