Vacuum Hot Pressing: Applications and Limitations

Introduction

Vacuum Hot Pressing (VHP) is a manufacturing technique that utilizes high temperature and pressure in a vacuum environment to consolidate and shape materials. It is commonly used in industries such as ceramics and is employed for both fundamental research and production purposes. VHP offers unique advantages in terms of achieving high density, uniform microstructures, and excellent mechanical properties in the manufactured materials. However, it also has certain limitations, such as the requirement for simple shapes and the need for sophisticated pressing dies for complex shapes. Let's explore the applications and limitations of Vacuum Hot Pressing in more detail.

Limitations of Vacuum Hot Pressing

Limited application for materials with low diffusion coefficients

Vacuum hot pressing is not suitable for materials that do not sinter to high densities due to low diffusion coefficients. In cases where a pore-free state is required for optimum mechanical, thermal, or optical properties, this process may not be effective.

Requires simple shapes for easy manufacturing

One of the limitations of vacuum hot pressing is that it is best suited for manufacturing parts with simple shapes like plates, blocks, and cylinders. Complex shapes may require a highly sophisticated design of pressing dies.

Sophisticated pressing dies are needed for complex shapes

In order to produce more complex shapes using vacuum hot pressing, sophisticated pressing dies are needed. These dies are designed to accommodate the intricacies of the desired shape and ensure proper molding and densification of the material.

The vacuum hot pressing method is commonly used in the field of ceramics for various applications. It is applied to materials such as MMC and CMC materials, composite materials, silicon nitride, mixed ceramics of Al2O3, TiC/TiN, and sialon for cutting tools, components of heavy-duty valves, bearings, and wear parts for process technology. It is also used for boron carbide (B4C) for extremely wear-resistant parts and armors, PLZT (lead-lanthan-zircon-titanate) and other high-developed functional ceramics, sputter targets, and SiC whisker reinforced Al2O3 for cutting tools.

The vacuum hot pressing method offers advantages such as shortening the sintering period, reducing the sintering temperature, and effectively improving the density of the target material. However, it also has some shortcomings. The thermal stress in the sintering process can lead to cracking of large-sized target bodies. Therefore, high uniformity and stability of the pressure and temperature field in the hot press are required. The mold material needs to be high due to die loss and reduction reaction with the target at high temperature, leading to poor homogeneity of the target microstructure.

Other disadvantages of the vacuum hot pressing method include limitations on the size of the obtained target, high requirements on mold materials, and low production efficiency. The method is not suitable for industrial continuous production and may result in poor uniformity of the target grain.

In comparison to hot isostatic pressing and air pressure sintering, vacuum hot pressing offers a more cost-effective solution for many manufacturers, especially in research institutions. The densification process of hot pressed materials involves plastic flow, viscous flow, diffusion, and creep, which can result in rapid densification and controlled microstructure when plastic and viscous flow are the dominant mechanisms.

Specifications of Pressing Force

• Range of pressing force: 50 kN to 800Ton
• Maximum applicable temperature: 2600°C
• Compatible component sizes: max. Ø 700mm to 1500mm

The press applies a fixed load (force) to the work between the platens. The pressure that is experienced by the work depends on the area over which the force is applied.

When using pellet dies for the pressing of powders, there is a trade-off between the size of the required pellet and the compaction pressure that can be achieved.

Pellet dies usually have a maximum rated load that limits the pressure to under 1000 MPa, but it can still be noted that a pressure of, say, 250 MPa can be achieved with as little as 0.5 tonnes in a pellet die of 5 mm. To achieve the same pressure in a 40 mm die, we need over 30 tonnes of load.

Common measures of plates:

• 2200 x 1100mm
• 2550 x 1100mm
• 2550 x 1350mm
• 2750 x 1350mm
• 3000 x 1350mm
• 3300 x 1350mm
• 3600 x 1350mm

In order to protect the pressing surfaces in a long-run and to simplify the process of cleaning, plastic foils which are glue-resistent can be spread over the pressing surfaces. Through fed presses with automatic feeding will use these foils also for the transportation of the workpiece through the press.

Vacuum hot pressing has a limited field of application for such materials which do not sinter to high densities due to low diffusion coefficients or for cases where a pore-free state is required (for optimum mechanical, thermal or optical properties).

With this process only parts with simple shapes like plates, blocks, cylinders can be manufactured easily. With a highly sophisticated design of pressing dies also more complex shapes can be produced.

Available pressing force: 50 kN to 800Ton at max. 2600°C, applicable for components of max. Ø 700mm to 1500mm.

Hot pressing technology is applied variously in fundamental research and production.

Application of hot pressing in the field of ceramics include:

• MMC and CMC materials, composite materials
• Silicon nitride, mixed ceramics of Al2O3, TiC/TiN and sialon for cutting tools, components of heavy-duty valves, bearings, wear parts for process technology.
• Boron carbide (B4C) for extremely wear resistant parts and armors.
• PLZT (lead-lanthan-zircon-titanate) and other high developed functional ceramic (O2 atmosphere)
• Sputter targets
• SiC whisker reinforced Al2O3 for cutting tools

KINTEK supplies a range of manual, power, motorized and automatic presses for XRF sample preparation. The Power Hydraulic Press operates in ranges between 8 and 200 tons. It is microprocessor controlled and loadable in metric and imperial tons for XRF and IR sample preparations.

WHAT SIZE PRESS DO YOU NEED FOR YOUR LAB?

• 5 Ton Press: Recommended for use with 3-15 mm diameter die sets
• 10 Ton Press: Recommended for use with 3-25 mm diameter die sets
• 25 Ton Press: Recommended for use with 8-32 mm diameter die sets
• 40 Ton Press: Recommended for use with 12-70 mm diameter die sets

These are suggested hydraulic presses, however, it will typically be determined by the largest diameter die you will be using. Please check the recommended force for good pellets and max recommended force on the product page for your pellet die. Indeed, you can make good pellets with relatively low pressing forces.

How are hydraulic presses used in laboratories? Many laboratory applications require pressure or heat to conduct various experiments. This includes compressing powders into mixtures for XRF analysis or pharmaceutical development, molding plastic or rubber material into samples for ASTM testing, analyzing the durability and strength of materials, along with prototyping and research and development projects.

KinTek offers many different styles of presses that would be ideal for your application. A standard selection of manual hand-operated benchtop presses with clamp forces up to 30 tons are available, as well as the AutoSeries line of programmable presses with user-friendly controls and clamp forces up to 48 tons.

KinTek also offers the Monarch series floor-standing industrial press with clamp forces up to 100 tons and capable of production use.

The compressive force in this press is developed by hand pressure on a lever attached to a large steel cam. This press system is designed to provide a steadily increasing mechanical advantage up to a ratio of approximately 50 to 1 at the end of the stroke. Thus, a force of 20 pounds applied to the lever develops approximately 1000 pounds on the press ram, which is adequate to produce firm pellets from most powdered materials (usually without adding a binder).

Features of the Hydraulic Press:

• Rugged and visually pleasing press.
• It is characterized by its simple and comfortable use.
• It incorporates recovery springs for the lower plate so that it is always in the ready-to-use position.
• It features an oleo-hydraulic system so that the oil does not escape from the chamber.
• Parts subject to wear and tear are made of hardened steel and ground and finished in epoxy paint.
• The width of the muffle allows you to insert and remove the muffle with the flange, saving time.

Technical Specifications of the Hydraulic Press:

• Height (low spindle): 510 mm.
• Width: 225 mm. Depth (without lever): 230 mm.
• Height: 235 mm.
• Width: 140 mm.
• Weight: 20 kg.
• Maximum piston stroke: 25 mm.
• Maximum power allowed: 15200 kg = 400 kg/cm2.
• Maximum recommended power: 9500 kg = 250 kg/cm2.

KinTek provides hand-actuated laboratory presses, which combine simplicity with excellence. Our presses, with capacity from 20 to 200 kN and cylinders with a return spring, are operator-friendly and need low maintenance, thanks to its trusted design. The standard press can heat up to 300 °C, for a 100 mm stroke, but we can adapt the stroke up to 200 mm, according to your need.

STANDARD LABORATORY PRESS RANGE (LAB PRESS) To equip laboratories or really small production units, we launched a varied range of standard laboratory presses. This new range allows the customer to choose the required performance while limiting the required investment. The LAB, LAB P (Programmable) & Lab PA (Programmable + data Acquisition) standard presses are equipped with high-temperature heating and cooling platens (up to 450 °C) and apply up to a 1,000 kN effort. These machines can perform the following processes:

• WORKING PRESSURE: 45,000 PSI (310Mpa)
• CONTROLS: Fully automatic (easy-to-use operator interface)
• THERMOCOUPLE: 4 each type C (Tungsten/Rhenium)
• VESSEL INTERIOR LENGTH: 24 inches (610mm)
• GRAPHITE FURNACE: A Graphite Furnace for use up to 2000°C
• HEATING RATE: Standard furnace rate up to 25°C per minute
• COOLING RATE: Up to 40°C per minute
• MAXIMUM SAMPLE SIZE: 60mm diameter x 300mm height

Applications of Hot Pressing

Hot pressing is a technique that is widely used in both fundamental research and production. It has found extensive applications in the field of ceramics. By utilizing hot pressing, manufacturers can eliminate the need for binders in their manufacturing process and instead use the combination of force and temperature to bond their parts completely.

Hot Pressing Furnaces are Used in a Variety Of Industries

Hot pressing furnaces are employed in various industries, including:

1. Aerospace Parts Manufacturers
2. Diffusion Brazing OEM’s
3. Advanced Ceramics Parts Manufacturers
4. Body and Vehicle Armor Manufacturers

These industries benefit from the use of hot pressing technology to create high-quality, durable parts.

Available Hot Press Furnaces

Hot pressing technology offers a range of available furnaces, with pressing forces ranging from 50 kN to 800 tons and temperatures of up to 2600°C. These furnaces are applicable for components with a maximum diameter of 700mm to 1500mm. They can be used to manufacture parts with simple shapes like plates, blocks, and cylinders. With the use of highly sophisticated pressing dies, more complex shapes can also be produced.

Applications of Hot Pressing in the Field of Ceramics

Hot pressing technology is widely applied in the field of ceramics. Some of its applications include:

1. MMC and CMC Materials: Hot pressing is used to create composite materials such as Metal Matrix Composites (MMC) and Ceramic Matrix Composites (CMC).
2. Cutting Tools: Hot pressing is employed to produce ceramics like silicon nitride and mixed ceramics of Al2O3, TiC/TiN, and sialon for cutting tools.
3. Heavy-Duty Components: Components of heavy-duty valves, bearings, and wear parts for process technology are manufactured using hot pressing.
4. Wear Resistant Parts and Armors: Hot pressing is used to create extremely wear-resistant parts and armors made of materials like boron carbide (B4C).
5. Functional Ceramics: Hot pressing is utilized to manufacture high-developed functional ceramics, such as PLZT (lead-lanthan-zircon-titanate), in an O2 atmosphere.
6. Sputter Targets: Hot pressing is employed to create sputter targets used in various industries.
7. Cutting Tools: Hot pressing is used to produce SiC whisker reinforced Al2O3 for cutting tools.

Other Applications

Apart from ceramics, hot isostatic pressing technology is also used in other areas, including:

1. Treatment of Castings
2. Powder Metallurgy
3. Porous Materials
4. Near-net Forming
5. Material Bonding
6. Plasma Spraying
7. Manufacture of High-end Graphite

Overall, hot pressing technology offers a wide range of applications in various industries, making it a valuable technique for manufacturing high-quality and durable parts.

Specific Applications in Ceramics

Manufacturing of MMC and CMC materials, composite materials

Composite materials, such as Metal Matrix Composites (MMCs) and Ceramic Matrix Composites (CMCs), play a crucial role in various industries. MMCs combine a metal with another substance, typically a ceramic or a polymer, to create materials with improved mechanical strength, biocompatibility, and imaging properties. Powder metallurgy is the most common method for producing MMCs, involving using a hydraulic press to compact the desired metal powder with a matrix material. This process allows for the creation of materials that are stronger and more durable than traditional materials, making them ideal for applications in medicine, aerospace, and more.

Production of silicon nitride, mixed ceramics of Al2O3, TiC/TiN and sialon

Silicon Nitride (Si3N4) is a high-performance ceramic material known for its exceptional mechanical, thermal, and electrical properties. It is extremely hard, has excellent thermal shock and impact resistance, and surpasses the high temperature capabilities of most metals. Mixed ceramics, such as Al2O3, TiC/TiN, and sialon, offer enhanced properties when combined with silicon nitride. These mixed ceramics exhibit high mechanical strength at high temperatures, wear resistance, acid and alkali corrosion resistance, self-lubricating properties, and high hardness. They are commonly used in industries such as aerospace, petroleum, and chemical engineering to replace traditional metal parts that may have limitations in terms of electrical insulation and security.

Use in components of heavy-duty valves, bearings, wear parts for process technology

Ceramic materials, including silicon carbide (SiC) and silicon nitride (Si3N4), are widely used in the manufacturing of components for heavy-duty valves, bearings, and wear parts in process technology. These ceramics offer excellent resistance to wear and abrasion, high mechanical strength at high temperatures, and resistance to corrosion. They are capable of withstanding extreme harsh conditions, making them ideal for applications in industries such as power, chemical and paper, oil drilling, automotive, and semi-conductive industries. The use of ceramics in these components ensures longevity, reliability, and improved performance.

Creation of boron carbide (B4C) for wear-resistant parts and armors

Boron carbide (B4C) is a unique ceramic material known for its exceptional hardness, high thermal and chemical stability, low density, and high neutron absorption cross-section. It is extensively used in the production of wear-resistant parts and armors. Boron carbide powder is commonly used for grinding, lapping, and polishing hard materials, while thin films of boron carbide are used as protective tribological coatings. Boron carbide's properties make it a potential candidate for high-temperature semiconductors, thermoelectric energy conversion, and optical materials development. Additionally, boron carbide is increasingly being investigated as an alternative to traditional gas-filled neutron detectors.

Development of PLZT (lead-lanthanum-zircon-titanate) and other high-developed functional ceramics

PLZT (lead-lanthanum-zircon-titanate) is a type of high-developed functional ceramic known for its unique piezoelectric and electro-optic properties. It is used in various applications such as actuators, sensors, transducers, and optical devices. PLZT ceramics possess the ability to convert electrical energy into mechanical energy and vice versa, making them essential in the development of devices that require precise control and manipulation of electrical and mechanical signals. These functional ceramics are extensively used in industries such as telecommunications, aerospace, medical devices, and consumer electronics.

Sputter targets production

Sputtering targets are thin discs or sheets of a material used in the sputtering process to deposit thin films onto a substrate. Sputtering is a widely used physical vapor deposition technique in modern technology and manufacturing. It involves bombarding the sputter target with ions, causing atoms of the target material to be ejected and deposited onto a substrate, creating a thin film. Sputter targets are used in a range of applications, including the deposition of transparent conductive coatings for LCD displays and touch screens in optoelectronics, decorative coatings for automotive parts and jewelry, and thin films for various electronic devices.

Production of SiC whisker reinforced Al2O3 for cutting tools

Silicon carbide whisker reinforced alumina (Al2O3) composites are widely used in the production of cutting tools. These composites combine the high hardness and wear resistance of silicon carbide with the toughness and heat resistance of alumina. The addition of silicon carbide whiskers to alumina improves the mechanical properties and wear resistance of the composite, making it an ideal material for cutting tools. The composites offer superior cutting performance, extended tool life, and improved productivity in industries such as metalworking, automotive, aerospace, and machining.

In conclusion, ceramics find specific applications in various industries, ranging from the manufacturing of composite materials to the production of wear-resistant components and functional devices. The unique properties of ceramics, such as high mechanical strength, wear resistance, thermal and chemical stability, and electrical properties, make them indispensable in critical applications where traditional materials may fall short.

Conclusion

In conclusion, vacuum hot pressing is a versatile technique with various applications and limitations. While it is limited in its use for materials with low diffusion coefficients and requires simple shapes for easy manufacturing, it can be highly effective in producing complex shapes with the use of sophisticated pressing dies. The pressing force range, maximum temperature, and compatible component sizes also make it suitable for a wide range of applications. In the field of ceramics, hot pressing is extensively used for manufacturing composite materials, producing wear-resistant parts, and developing high-functioning ceramics. Overall, vacuum hot pressing offers a valuable solution for achieving precise and high-quality ceramic components.

If you are interested in this product you can browse our company website:https://kindle-tech.com/product-categories/heated-lab-press, we always insist on the principle of quality first. During the production process, we strictly control every step of the process, using high quality materials and advanced production technology to ensure the stability and durability of our products. to ensure that their performance meets the highest standards. We believe that only by providing customers with excellent quality can we win their trust and long-term cooperation.