Compositional modification of Ni-base alloys for laser-deposition technologies

Cracking of the clad layers is a major issue in laser cladding of hard wear-resistant coatings such as Ni-Cr-B-Si-C alloys. One way to solve this problem is to increase the toughness of these alloys by compositional and microstructural modifications. The focus of this chapter is on defining a procedure to select alloying elements for microstructural refinement of Ni-Cr-B-Si-C alloys and assessing the effectiveness of such a refinement as a toughening mechanism to solve the cracking problem of laser deposited coatings. It is shown that the addition of Nb in specific quantities induces a significant microstructural refinement while preserving the original level of hardness. However, cracking susceptibility of the microstructurally refined deposits was not decreased because the continuous network of hard eutectics still provided an easy route for crack growth. Consequently, an effective toughening mechanism for Ni-Cr-B-Si-C alloy deposits should include not only refinement of the hard precipitates, but also modification of the eutectic structure