Thermal spray alloy powder for use in high temperature environments

       Superalloy powder is a kind of alloy powder developed to meet the requirements of high temperature use. W, Mo, Ni, etc. These strengthening elements mainly strengthen the superalloy in three ways: one is solid solution strengthening, adding alloying elements into the base metal to form single-phase austenite for strengthening; Precipitation of dispersed carbides or intermetallic compounds to strengthen; the third is grain boundary strengthening. Superalloys are divided into three categories according to their matrix composition: nickel-based superalloys, iron-based superalloys and cobalt-based superalloys.



MCrAlY is the most commonly used thermal spraying superalloy material at present, wherein M represents the matrix element, which is one or two of the three metal elements of Fe, Ni and Co. According to the different matrix elements, there are the following categories:



FeCrAlY is suitable for working in a carburizing environment, showing excellent sulfidation resistance, low price and good plasticity, but its microstructure is ferrite, which does not match the matrix structure of general superalloy workpieces, so it is generally not suitable for nickel-based and high-temperature alloy workpieces. Cobalt-based alloys are used on the surface of workpieces; NiCrAlY has good ductility and oxidation resistance, but poor sulfidation resistance, and is better used in aero-engines; CoCrAlY has high sulfidation resistance, but low oxidation resistance and ductility, suitable for Working in the environment of ships and ground industrial gas turbines; NiCoCrAlY and CoNiCrAlY, these alloys have both the advantages of NiCrAlY and CoCrAlY, and have better overall performance.



The oxidation resistance and corrosion resistance of MCrAlY coatings are based on the formation of dense Cr2O3 or Al2O3 oxide films on the coating surface. These oxide films act as oxygen diffusion barriers, preventing further oxidation or corrosion of the substrate or bonding layer.



High temperature alloy powder is generally sprayed by plasma spraying and supersonic flame spraying.