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Vacuum sintered ceramics are used as auto parts

High-temperature structural ceramics are used in various devices, equipment and structures, and can withstand various static or dynamic mechanical loads under high temperature conditions. It has the advantages of high melting point, high temperature strength, small high temperature creep, good thermal shock resistance, corrosion resistance, oxidation resistance and structural stability. High-temperature structural ceramics include high-temperature oxides and high-temperature non-oxides (or refractory compounds). As a structural material, metal is not suitable for use at high temperatures because it is susceptible to corrosion and is not resistant to oxidation at high temperatures. The emergence of high-temperature structural ceramic materials has made up for the weakness of metal materials and has been widely used.
Due to the advantages of high-temperature structural ceramic materials such as excellent heat resistance, wear resistance and light weight, the use of ceramic materials instead of metal to prepare heat engine components has attracted great attention from all over the world. Ceramic parts have been widely used in aviation, transportation, machining and other fields. The ceramic parts used in the engine can achieve the effects of reducing friction, anti-wear, low inertia and saving fuel. With the continuous prominence of the advantages of ceramic parts, its application has become more and more extensive. Taking the valve, a key component of the engine, as an example, the application of high-temperature ceramics in the engine is introduced, and its preparation method is given.

Advantages of ceramic valves:
The intake and exhaust valves are one of the important parts of the engine. Using high-temperature structural ceramic materials to make the valves can avoid the valve burning problem under high heat load. In addition, the valves are the main moving parts in the engine valve train. The inertial load and elastic vibration characteristics of the valve train have a great influence. Using low-density ceramic material as the valve can increase the upper limit of the speed at which the valve train can work normally. It is also possible to use a cam profile with greater acceleration without increasing the rotating speed, so that the amount passage area of the valve port is increased, thereby improving the inflation coefficient and power of the engine. It is also possible to use a weaker valve spring without changing the speed and cam profile, so that the inertial force and spring force load acting on the valve train can be reduced, so as to reduce the mechanical loss and wear rate of the valve train. In short, the ceramic valve is one of the engine ceramic parts with high potential use value.
Pressureless sintering of ceramic valves:
The ceramic valve is a complex-shaped component with a slender upper section and a large-diameter conical lower end. The harsh working environment of ceramic valves requires ceramic valves to have high heat resistance, high temperature gas corrosion resistance and wear resistance. Therefore, to obtain high-performance ceramic valve components, the preparation process requirements are quite strict. Therefore, the vacuum sintering furnace of SIMUWU is used for pressureless sintering. The specific process is as follows:

The ceramic valve prepared by the pressureless sintering process has the following advantages:
(1) Since the direct cold isostatic pressing is used to form a silicon nitride ceramic valve with a near net size at one time, the work efficiency is greatly improved and the loss of raw materials is reduced.
(2) The processing procedure of the ceramic valve blank is avoided, thereby improving the yield.
(3) The machining allowance of the blank after sintering is reduced.
(4) The pressureless sintering process is low in cost and easy to operate.
In summary, this process route has the advantages of low cost, high efficiency and easy mass production. After the qualified ceramic valve is installed in the diesel engine, it has good running performance, long service life, and is economical, which improves the overall quality of the diesel engine product.
Selection of sintering equipment: High-quality ceramics must be manufactured with high-quality equipment. The RVS series vacuum sintering furnace produced by SIMUWU is a vacuum sintering furnace suitable for high-temperature structural ceramics including boron carbide and silicon carbide ceramics. It has the advantages of good temperature uniformity, high vacuum degree, automatic control, etc. It is an ideal product for processing boron carbide ceramics.