The main functions of niobium in ultra - heat - resistant alloys are solid solution strengthening and precipitation strengthening. Niobium forms carbide in the form of MC and M6C to form Ni3Nb double reinforced phase. The creep resistance of niobium in ultra - heat - resistant alloy was improved by solid solution and Ni3Nb double - phase precipitation.
The demand for niobium-based ultra-heat resistant alloys mainly depends on the aero-engine industry. In any case, that reliance has declined in recent years, mainly in the case of car engines. General electric's f-engine USES the Inconel706 as the main hull. The next generation H engine will use Inconel718, a super heat resistant alloy that requires a higher niobium content. Although the consumption of nickel-based alloys in the automotive industry is still very small, new regulations and social policies have placed higher requirements on alloys in a variety of areas such as high temperature exhaust systems, making these alloys increasingly important in the automotive industry. Inconel625 is one of the materials of choice and has been used in many applications in the automotive industry. Figure 1 shows the importance of 718 alloys in the aero-engine industry. The heat resistant alloys used in a new type of engine, such as the Inconel718, account for 35% of its total weight.
Nickel-based alloy manufacturers consume niobium in different forms, depending on their ability and the end use of the alloy. Niobium oxide (Nb2O5) can be used to reduce waste consumption during direct ni-niobium ingot reduction heating, especially in the case of Inconel718 production. The intermediate product can be used as the parent alloy in the manufacture of the final nickel base alloy. Vacuum grade ferric niobium (66wt%Nb) and nickel niobium alloy (66wt%Nb) are directly added to the smelting furnace as parent alloys to make ultra-heat resistant alloys. These parent alloys use high purity niobium oxide as raw material. The final product is obtained by aluminum thermal reaction. Figure 2 shows 2 tons of niobium ingot before sizing after cleaning. Niobium can be used as a casting alloy under some special environmental conditions.
