Character of Hot Crack Formation During Welding of Cast Heat-Resistant Nickel Alloys

Heat-resistant nickel alloys are the main structural materials used to manufacture gas turbine engines widely applied in aircraft engineering and other industries. Engine sections for high-temperature operation are made using precipitation-hardening nickel alloys with intermetallic strengthening. To ensure the structure stability and maintain high long-term strength properties, nickel alloys are provided with complex alloying systems containing γ'-forming elements (Al, Ti, Nb), the total content of which in an alloy amounts to 6–15 % or more. Complex alloying systems and high strength properties of the alloys lead to crack formation in the weld and heataffected zone in welding metal of even small thickness. This stipulated the interest in investigating the principles of hot crack formation first of all in the heat-affected zone during fusion welding in terms of structural transformations. Investigations were conducted on nickel alloy IN 738 used as a structural material for the manufacture of gas turbine blades. The chemical composition of the alloy is given in Table 1.