Thermal fatigue of single-crystalline superalloy CMSX-4 (R): a comparison of epitaxial laser-deposited material with the base single crystal

The thermal fatigue resistance of cast single-crystalline CMSX-4 samples fe aturing an edge composed of a 1-mm-deep layer of laser-deposited epitaxial single-crystalline CMSX-4 is compared with that of samples made entirely of the virgin base material. Tests are conducted by cycling between 200 and 1 100 degreesC, and recording the progression of the largest crack growing in each sample. It is found that crack growth rates in samples with laser cla ddings are around twice those in the base material; this is chiefly attribu ted to their different thermal history. Resistance to crack initiation was lower in two out of three laser-clad samples than in the base material; thi s is attributed to interdendritic flaws in laser-clad layers of these two s amples. The performance of the third coated sample was comparable with that of the base material. (C) 2001 Elsevier Science B.V. All rights reserved.