Heat-resistant castings need to effectively add alloying elements to their steels during operation, so that they can effectively increase the bonding force between their atoms and form their favorable structure to a certain extent by adding their chromium. Molybdenum, tungsten, vanadium, titanium and so on, can strengthen the steel matrix, raise recrystallization temperature, but also form strengthened phase carbides or intermetallic compounds.
The heat resistant castings are stable at high temperature and will not dissolve and grow up during operation. Thus the hardness of the castings can be effectively maintained to a certain extent and nickel elements are added mainly to obtain austenite. The atoms in austenite are more compact than those in ferrite, and the bonding force between atoms is strong, and the diffusion of atoms is difficult. So the austenite has good high temperature strength. Therefore, the high-temperature strength of heat-resistant steel is not only related to chemical composition, but also to microstructure.
Effect of chemical composition on service life of heat-resistant castings
In the process of operation, many chemical elements can affect the service life of the product to a certain extent. These effects are mainly manifested in the stability of the reinforced structure, the effective prevention of its oxidation, the formation and stability of austenite, corrosion prevention and so on.
The rare earth elements of trace elements in heat-resistant castings can to a certain extent significantly improve the oxidation resistance of their steels, so that their thermoplasticity can be changed to a certain extent, and the basic materials of their heat-resistant steels and alloys generally have a higher melting point. Since the self-diffusion activation energy is large and the smelting process is required for various heat-resistant steels and superalloys, it is also of great significance to study the action of chemical substances.
Effect of laser shock on service life of heat-resistant castings
In the process of operation, the heat resistant castings were treated with laser shock, and the fatigue tensile test was carried out under the conditions of 25400500 and 600 degrees Celsius, and the mechanical properties of the heat-resistant steel specimens were tested at different temperatures.
It is found that the yield strength and elastic modulus of heat-resistant castings after laser hardening can be increased obviously and increase with the increase of temperature. Temperature has a great influence on the life of heat-resistant steel. With the increase of temperature, the fatigue life of heat-resistant steel decreases significantly. Laser technology is the most effective method to improve the fretting fatigue resistance of materials at room temperature in recent years.http://www.wuxiorient.com/