Benefits of HIP. What Is HIP? What Does It Do?
Hot isostatic pressing (“HIP”) involves the application of high pressures and temperatures through the medium of a pressurizing gas such as argon or nitrogen. HIP consolidates powders of metals, ceramics, or carbides info fully dense, complex parts with nel or nearnet shapes. or info very high quality forging billers HIP .’heals” defects in castings by creep mechanisms and/or compressive plastic deformation. The clean void surfaces are bonded together by diffusion. HIP is also used for diffusion bonding dissimilar materials, and for applying wear. or corrosion resistant coatings to parts exposed to stringent operating conditions.
By consistently improving materials’ mechanical properties and by narrowing the scalter band of properties. HIP enables designers lo utilize a very high proportion of the physical strength of materials. This translates into higher reliability and longer service lile, or into smaller, lighter-weight parts, or both.
By reducing rejection rates and scrap losses, minimizing or eliminating machining costs, and consuming less energy, HIP can reduce the total production costs ol a product. following are some of the specific advantages imparted by HIP to several specific categories ol materials or processes.
Containerized niches based alloy powder is Hip’ed cut into segments, centerlessground, and forged into high pressure turbine disks wilh belier properties than wrought disks.
HIP reduces total casting costs by reducing rejections and scrap losses. Eliminates closed voids, micro. porosity, and shrinkage tears. Improves ductility and fatigue properties, often to Ihe equivalent of forged or wrought pats. Improves reliability and Service life. Permits smaller, lighter-weight castings to be used. Upqrades the properties of difficult-to-cast materials Such as titanium and certain superalloys to acceptable levels. Rejuvenates mechanical properties of service. fatigued parts lo new or nearly new levels.
HIP’ing complex parts to net or near-net shape sharply reduces input weight, thereby reducing and in some cases eliminating- machining costs. Produces line grained, homogeneous microstructures with superior mechanical properties which increases reliability and service life. Reduces scrap losses. Enables alloy combinations 1O be produced which are impossible to allain by other means. HIP conserves costly strategical materials and reduces total energy usage.
Eliminates voids and microporosity which are stress risers. This improves transverse rupture strength and wear resistance. Permits the use of fine grained, low cobalt mixes which have particularly good wear resistance but which are difficult to manufacture without voids and microporosity. Extends the service life of expensive canning tools, drawing dies, and rolling mills. Reduces rejection rates and scrap losses, and enables scrap to be recycled. Helps prevent very costly premature failures of tricone oilwell rock bits.
Advanced engineered ceramics are brittle and have poor tolerance to thermal shock. Once cracks develop at flaws or microporosily, ceramics fail rapidly. By eliminating flaws and porosity, HIP provides striking improvements in ceramics’ performance and useful lifetime. HIP’ing ceramics to net or near-net shape is also a major advantage because these materials are too hard to machine cost effectively.
By removing porosity and producing fully dense material, HIP maximizes the strength of medical prostheses and prevents premature failure.
|A 4140 valve body HIP clad with IN 625 corrosive service. These valves are now in production, they cost far less than solid IN 625 valves.||Cast Nickel-base impeller||As sintered Ti 6AI 4V after HIPing, 545 X magnification, unetched Density is 100% of theoretical Note absence of large rounded pores and spheroidization of small non-metallic inclusions.|
Typical Improvements Resulting From HIP
- Fatigue life of aluminum castings improved 300 percent
- Ultimate tensile strength of high chromium iron castings increased from 91,000 psi to 151,000 psi
- Rejection rate of 17-4 PH impellers reduced from almost 90 percent to nearly zero
- Scrap rate of military turbine engine blades reduced by 75 percent
- Fatigue life of superalloy medical prosthetic devices increased by a factor of 10
- Service life of silicon nitride cutting tools increased by 400 percent
- Buy-to-fly ratio of complex titanium parts improved from 7.5:1 to 3 5:1.