Hot Isostatic Pressing

Hot Isostatic Pressing for Platinum Group Metals

What does Hot Isostatic Pressing (HIP) do for Platinum  Castings?

  • HIP or Hot Isostatic Pressing Process on Platinum eliminates sub-surface porosity in jewelry castings.
  • HIP makes platinum measurably stronger and more ductile due to the increased density.
  • Improves the speed and quality of bench operations through denser and more uniform microstructure.
  • Provides a more durable product for the consumer.

HIP or Hot Isostatic Pressing is a high-pressure thermal treatment that is commonly used on investment castings in quality-critical industries such as medical and aerospace. TechForm uses this process to create high-quality castings for the jewelry industry. The HIP  process involves placing the castings into a high-pressure vessel with inert gas and applying pressure at elevated temperatures. The result is densification, which happens when the metal’s creep resistance is surpassed and plastic flows and enables the surrounding material to move into subsurface voids. Time at temperature allows diffusional bonding to occur, which eliminates internal porosity.

Below are magnified images of ring cross-sections showing the interior of a typical 950 PtRu casting before and after HIP. As one can easily see, almost no porosity is left after the HIP treatment.

Hot Isostatic Pressing hip
HIP Eliminates internal porosity in platinum castings.

Mechanical Properties of HIP

All of the platinum alloys we tested after HIP resulted in increased yield strength and ultimate tensile strength. While these properties are important they are not necessarily critical to predict failure in jewelry castings. When it comes to fatigue life, (bending, forming, stretching) the elongation and reduction of area properties are generally viewed as most important. For 950 PtRu and 900 PtRh, a very significant increase in elongation and ROA is achieved through HIPing. 900 PtIr, with its comparatively low porosity, is only minimally affected by HIP. These results are a clear indication that reduction in porosity increases ductility.

For an in-depth look, read Teresa Frye’s research on The Effects of Hot Isostatic Pressing of Platinum Alloy Castings on Mechanical Properties and Microstructures.

Alloy Composition & ConditionYS[MPa]UTS[MPa]ε [%]ROA[%]ROA %Change
95Pt5Ru – As-Cast
225
412
30
55
95Pt5Ru – HIPed
236
420
39
87
+32
90Pt10Ir – As-Cast
219
353
33
90
90Pt10Ir – HIPed
226
358
36
87
-3
90Pt10Rh – As-Cast
140
330
37
64
90Pt10Rh – HIPed
144
333
43
89
+25
Hot Isostatic Pressing of Platinum Castings
Patrick in the HIP room
HIP
Hot Isostatic Pressing jewelry castings
Loading into the HIP furnace