Microstructure and Wear Resistance of Ni-Cr Alloy Laser Cladding Layer with High Cr Content

Abstract:

Four kinds of Ni-xCr alloy laser cladding layers (x=20, 40, 60 and 80, wt%) were prepared by high-speed laser cladding technique, and the relationship between microstructure and wear resistance of Ni-Cr alloy laser cladding layers with different Cr contents was investigated. The results show that the four Ni-Cr alloy laser cladding layers all have reticulated dendritic structures. Among them, Ni-20Cr and Ni-40Cr are single-phase γ-(Ni, Cr) solid solutions, and their wear mechanisms are adhesive wear and abrasive wear. With the increase in Cr content, Ni-60Cr and Ni-80Cr are γ-(Ni, Cr) phase and Cr phase, as well as Cr-rich precipitates, and their wear mechanisms are adhesive wear, abrasive wear and fatigue wear. A moderate increase in Cr content can enhance the hardness and wear resistance of Ni-Cr alloy laser cladding layer. However, excessive addition of Cr results in the precipitation of Cr-rich precipitates. The hardness of these precipitates is 2430.4 MPa, which is lower than the hardness of the Ni-60Cr matrix (4024.86 MPa) and Ni-80Cr matrix (7022.68 MPa). A hardness transition zone exists between the Cr-rich precipitates and the matrix. Cracks are likely to initiate and expand in this zone, leading to deep spalling, which is not conducive to the wear-resistant properties of the laser cladding layer. Ni-80Cr has the highest hardness, but its high Cr content leads to a large number of penetrating cracks and Cr-rich precipitates on the surface, ultimately resulting in the worst wear resistance. Ni-60Cr exhibits the best wear resistance due to its high hardness and dense microstructure.

Key words:Ni-Cr alloy;laser cladding;Cr-rich precipitate;wear resistance