In the first part of the article we discussed about powders and the classifications adopted for cemented carbide, as well as the importance of using a proper dewaxing cycle.

In this second part we will go more in depth about the sintering process, discussing the difference between vacuum sintering and sinter-HIP for cemented carbide and the equipment.

Sintering

Vacuum furnaces can be designed to carry out both thermal dewaxing and sintering on the same piece of equipment. In that case, furnaces are equipped with a wax trapping system and a box with calibrated gas nozzles for an homogeneous gas flow distribution. The gas flow distribution is critical to efficiently remove wax vapors from the parts and ensure an optimal temperature uniformity.

TAV VACUUM FURNACES HM Series - Sinter-HIP furnace equipped for hydrogen overpressure operation. 
The electrically fired H2 burner is visible on top of the furnace.

However, separated dewaxing furnaces are sometimes used to improve productivity and cleanliness on the sintering furnace. In the that case, even if dewaxing is generally completed at temperatures below 500°C, parts are heated to higher temperatures approaching 1000°C as a pre-sintering step, to ensure sufficient strength on the parts to be moved to the sintering furnace.

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In the first part of the article, we discussed how different designs impact the efficiency of vacuum furnaces in respect to their heating energy requirements.
Even though the energy used for heating undoubtedly represents the main energy consumption during vacuum heat treatments, several auxiliary systems can be present on vacuum furnaces (or in the plant housing the furnace); just think of the water-cooling system, the gas quenching system and, clearly, vacuum pumps.
Those auxiliary systems are essential to ensure proper functioning of a vacuum furnace, however, they can generate altogether a significant energy consumption source, especially when continuous operation is required.

Vacuum Pumps

Vacuum pumps are the components that allow a sealed, leak tight furnace to reach the desired vacuum level before starting the heat treatment.

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As we all know, global events have led to a significant increase in energy cost in the past two years all over the world.

In Europe, current natural gas prices (February 2023) have more than doubled compared to the same period of 2020. In Italy, the cost of one MWh of electrical energy is about 3 times what the cost was just 1 year ago. Moreover, the strong price uncertainty makes difficult for companies to forecast the energy-related costs involved for the next few months.

Energy-intensive industries are largely impacted by price inflation; among them foundries, the metalworking industry and, of course, commercial heat treaters and companies performing in-house heat treatment of any sort.

Heating a load to a determined temperature for some time requires a certain amount of energy; whether that energy is generated from fossil fuel (coal, natural gas, petroleum) or renewable resources (solar power, wind power, hydropower), that is an inescapable reality.

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