高Cr含量的Ni-Cr合金激光熔覆层组织与耐磨性能

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

摘要:

采用高速激光熔覆技术制备了4种Ni-xCr合金熔覆层（x=20、40、60和80，质量分数），研究了不同Cr含量的Ni-Cr合金熔覆层的显微组织与耐磨性能的关系。结果表明，4种Ni-Cr合金熔覆层的组织均为网状枝晶结构。其中，Ni-20Cr和Ni-40Cr为单相的 γ-(Ni, Cr)固溶体，其磨损机制为粘着磨损和磨粒磨损。随着Cr含量的增加，Ni-60Cr和Ni-80Cr为γ-(Ni, Cr)相和Cr相，且存在富Cr沉淀物，磨损机制为粘着磨损、磨粒磨损和疲劳磨损。适度增加Cr含量可以提高Ni-Cr合金熔覆层的硬度和耐磨性。然而，过量添加Cr会导致富Cr沉淀物的析出。这些沉淀物的硬度为2430.4 MPa，低于Ni-60Cr基体（4024.86 MPa）和Ni-80Cr基体（7022.68 MPa）的硬度。富Cr沉淀物与熔覆层基体之间存在硬度过渡区，裂纹极易在过渡区萌生并扩展，造成深层剥落，不利于熔覆层的耐磨性能。Ni-80Cr的硬度最高，但其Cr含量过高导致表面存在大量的贯穿性裂纹和较多的富Cr沉淀物，最终表现出最差的耐磨性能。Ni-60Cr拥有较高硬度和致密的微观结构，因此表现出最好的耐磨性能。

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.