SOLIDIFICATION AND MICROSEGREGATION BEHAVIORS OF NICKEL-BASE SINGLE CRYSTAL SUPERALLOY SOLIDIFIED AT MEDIUM COOLING RATE
(State Key Laboratory of Solidification Processing,Northwestern Polytechnical University, Xi′an 710072, P. R. China)
Abstract: Single crystal blades have already been used in some advanced engines. An industrially valuable nickel-base single crystal superalloy CMSX-2 was solidified at cooling rate from below 1 K/s to 20 K/s. Microstructure and microsegregation were investigated. The results showed that the dendritic arm spacing is highly refined at high cooling rate, the primary dendritic arm spacing can be 35μm, just as 1/10 as that by conventional HRS processing. With the increase of cooling rate, the microsegregation increases and then decreases. In the superfine columnar dendrite, theγ′precipitates are very fine; the amount ofγ/γ′eutectic is much fewer and its size is very small.
Key words: single crystal superalloy cooling rate microstructure microsegregation