What is the definition of stellite alloy welding?
Stellite alloys are cobalt-based alloys that contain considerable amounts of nickel, chromium, tungsten, and a small amount of molybdenum, niobium, tantalum, titanium, lanthanum, and occasionally iron.
According to the composition of the alloy, they can be made into welding wire, powder for hard surface welding, thermal spraying, spray welding and other processes can also be made into casting and forging parts and powder metallurgy parts.
What is the usage of stellite alloy welding?
According to the usage, Stellite alloy can be divided into Stellite wear resistant alloy, Stellite high temperature resistant alloy and Stellite wear resistant and aqueous solution corrosion alloy.
In general working conditions, both wear resistance and high temperature resistance or wear resistance and corrosion resistance are required. In some working conditions, high temperature resistance, wear resistance and corrosion resistance may also be required at the same time. The more complex working conditions are, the more the advantages of Stellite alloy can be embodied.
What are the types of stellite alloy welding?
Typical types of Stellite alloy are:
Stellite E1, Stellite4, Stellite6, Stellite8, Stellite12, Stellite20, Stellite21, Stellite31, Stellite100, etc
What is the difference between stellite alloy welding and others ?
Different from other alloys welding, Stellite alloys welding are not strengthened by orderly precipitation phase which is firmly bound to the matrix, but by austenite FCC matrix which has been strengthened by solid solution and a small amount of carbides distributed in the matrix. Casting Stellite alloys welding , however, relies heavily on carbide strengthening. Pure cobalt crystals have a dense hexagonal (HCP) crystal structure below 417 ° C, converted to FCC at higher temperatures.
In order to avoid this transition during the use of Stellite alloys welding, virtually all Stellite alloys are nickel alloyed to stabilize the structure from room temperature to melting temperature. Stellite alloys exhibit a flat fracture stress-temperature relationship, but exhibit superior thermal corrosion resistance over 1000℃ compared to other high temperatures, possibly due to the high chromium content of the alloy, a characteristic of this type of alloy.
What is the characteristics of satellite alloy welding ?
It has high strength, good thermal fatigue resistance, thermal corrosion resistance and abrasion resistance, and good weldability. It is suitable for making the guide vane and nozzle guide vane of aviation jet engine, industrial gas turbine, ship gas turbine and diesel engine nozzle, etc.
Stellite alloy has excellent thermal corrosion resistance, and it is generally believed that the reason why Stellite alloy is superior to nickel-based alloy in this respect is that the melting point of cobalt sulfide (such as co-CO4S3 eutectic at 877℃) is higher than that of nickel sulfide (such as Ni-NI3S2 eutectic at 645℃), and the diffusivity of sulfur in cobalt is much lower than that in nickel. And because most Stellite alloys contain more chromium than nickel-based alloys, they form on the alloy surface resistant to alkali metal sulfates (such as a Cr2O3 coating corrode by Na2SO4). But Stellite alloys generally have much lower oxidation resistance than nickel-based alloys.