Several Factors Affecting the Lifespan of Molybdenum Disilicide Heating Elements
(1) Operating Mode: Elements in continuous operation furnaces have a longer service life than those in intermittent furnaces. This is because the protective film on the surface of molybdenum disilicide elements becomes thinner due to repeated temperature fluctuations.
Continuous Operation: During prolonged high-temperature continuous operation, the surface film of molybdenum disilicide gradually evaporates, leading to thermodynamic phase equilibrium from the interior to the surface. When the silicon concentration gradient on the surface is insufficient to form low-silicide phases, free molybdenum oxidizes and volatilizes, forming a quartz glass protective film on the new molybdenum silicide interface. This continuous process of volatilization and film formation causes the element to gradually thin until it eventually burns out at localized small cross-sections due to overload. This is primarily the failure mode in continuous kilns.
Intermittent Operation: The quartz glass film on the surface of molybdenum disilicide cracks, spalls, and thins due to thermal expansion and contraction during heating and cooling cycles. A new protective film forms on the cracked or spalled surfaces, creating pits that are lower than the element's surface. After repeated cycles, the element's surface develops continuous pitting with diameters of 1–2 mm and depths of 0.2–0.5 mm, eventually leading to burnout at thin cross-sections due to overheating. This is primarily the failure mode in intermittent furnaces.
Molybdenum disilicide heating elements are more suitable for long-term operation, especially in large high-temperature kilns such as tunnel kilns, where their characteristics are better utilized under continuous operation.
(2) Surface Load: Selecting the surface load of the element based on the furnace structure, atmosphere, and operating temperature is also a key factor. Surface load refers to the rated power allowed per unit surface area of the heating section of the element.
(3) Furnace Environment: The atmosphere and substances inside the furnace are critical. Contact with gases such as water vapor, hydrogen, halogens, as well as aluminum, silicates, molten metals, and metal oxides can cause corrosion or oxidation.
(4) Wiring Method and Furnace Operation: These are two factors that should not be overlooked. Molybdenum disilicide elements are typically connected in series.
Molybdenum disilicide manufacturers produce and customize large-diameter molybdenum disilicide rods. Models include 1700-type and 1800-type. Inquiries are welcome.

Molybdenum disilicide is a resistive heating element that is brittle and hard at low temperatures. During installation, replacement, storage, and transportation, external force should be avoided. Its electrical resistance is low at low temperatures and increases rapidly with rising temperature. At a constant temperature, the resistance remains stable and does not change over time, allowing new and old elements to be used together. At high temperatures, it softens slightly and exhibits some plasticity. During installation, it should be spaced apart from the furnace lining. When wiring, it should not be tightened too much initially; it should be tightened again at high temperatures to prevent breakage. The high-temperature oxidation resistance of molybdenum disilicide is primarily due to a protective silicon dioxide film on its surface, which has a melting point of 1710°C. During prolonged high-temperature use, this protective film may evaporate, crack, or spall, but it will regenerate under high-temperature oxidizing conditions, forming a new high-temperature-resistant silicon dioxide protective film.