Skin Effect of Hf-Rich Melts and Some Aspects in Its Usage for Hf-Containing Cast Nickel-Base Superalloys

On Liquation and Liquid Phase Oxidation during Linear Friction Welding of Nickel‐Base IN738 and CMSX Superalloys

“…Similarly, at 1350 o C, where significant bulk melting occurred in CMSX 486 superalloy, type 2 oxide scale was observed on the exposed surface of melted regions, which re-solidified with a completely new dendritic microstructure (Figure 9). A similar hafnium-base oxide, suggested to be based on HfO 2 and with a metallic composition that is consistent with that of the type 2 oxide scale observed in this present work, has been reported to form by oxidation of hafnium-rich liquid during casting of a hafnium-bearing nickel-base superalloy [11].…”

“…Hafnium selectively partitions into interdendritic liquid during solidification of nickelbase superalloys, including CMSX 486 superalloy. Selective partitioning of hafnium was reported to result in the formation of nickel-hafnium intermetallic phases by eutectic-type terminal solidification reaction in front of γ-γ' eutectics in nickel-base superalloys [11,12].…”

On Liquation and Liquid Phase Oxidation during Linear Friction Welding of Nickel-base IN 738 and CMSX 486 Superalloys

“…Some of the liquid exposed to the atmosphere at the mating surfaces of the work-pieces appeared to have reacted with oxygen to produce the continuous hafnium-base and aluminum-rich oxide films along the weld lines of CMSX 486 and IN 738 superalloys, respectively. Formation of continuous oxide films has been reported to be detrimental to the mechanical properties of nickelbase superalloys [11,16]. Consequently, the observed formation of continuous oxide films along the weld lines of the linear friction welded CMSX-486 and IN 738 superalloys could be detrimental to the mechanical integrity of the weld joint.…”

Development of tool for physical simulation of skin formation during investment casting of nickel-based superalloys

“…The skin formation depends on casting conditions, such as melt and mould temperature, mould geometry and cooling conditions. There is a body of experimental research on skin formation during casting of Al alloys [6,7], Mg alloys [8][9][10] and cast iron [11][12][13], whereas the research on skin formation during investment casting of Ni-based superalloys is surprisingly very limited [14]. The prediction and control of the thickness of skin is considered as a challenge in casting technology [3].…”