Cr12MoV钢表面激光熔覆多层Ni基合金涂层的组织及性能

Microstructure and properties of laser clad multi-layer Ni-based coating on Cr12MoV steel surface

使用脉冲Nd∶YAG激光器在Cr12Mo V模具钢表面熔覆了Ni20Cr和Ni60A多层Ni基合金耐磨涂层,并使用X射线衍射仪、扫描电镜及能谱仪分析了涂层的物相和显微组织。同时运用显微维氏硬度计以及高速往复摩擦磨损试验机对比分析了涂层与基体的硬度及耐磨性。结果表明,采用Ni20Cr作为打底层的多层Ni基合金涂层,能有效改善涂层与基体的冶金结合,大大减少涂层中的裂纹、气孔等缺陷。涂层表面物相主要为"-(Fe,Ni)、Fe Ni3、BNi3、Cr3C2以及Ni-Cr-Fe;涂层底部至表面的组织为胞状树枝晶、柱状树枝晶、择优生长树枝晶以及等轴树枝晶。Ni60A涂层大大提高了Cr12Mo V模具钢的表面硬度,涂层表面显微硬度最高可达到1000 HV0.2,是基体的1.6倍。Ni60A涂层耐磨损性能明显优于基体,较基体提高了2.0~3.3倍。在Cr12Mo V模具钢表面激光熔覆多层Ni基合金涂层后,形成了Cr3C2、Ni-Cr-Fe等硬质相,可有效提高其表面的硬度和耐磨性,起到降低模具在使用过程中因摩擦磨损而报废的概率,从而进一步延长模具的使用寿命。

Ni20 Cr and Ni60 A multi-layer Ni-based alloy wear resistant coating was prepared by laser cladding on the surface of Cr12 MoV die steel by pulsed Nd∶YAG laser,the phases and microstructure of the coatings were analyzed by using X-ray diffractometer,scanning electron microscope,and energy spectrometer,meanwhile the hardness and wear resistance of both the coating and the substrate were analyzed by using Vickers microhardness tester,high-speed reciprocating friction and wear tester.The results show that using the Ni20 Cr as the underlying layer of the multi-layer alloy coating can effectively improve the metallurgical bond between the coating and the substrate,which can greatly reduce the defects such as cracks and pores in the coating.The main phases of the coating surface are"-(Fe,Ni),Fe Ni3,BNi3,Cr3C2 and Ni-Cr-Fe.The structure of the coating from bottom to surface in turn is cellular dendrites,columnar dendrites,preferentially growing dendrites and equiaxed dendrites.The Ni60 A coating can greatly improve the surface microhardness of Cr12 MoV die steel,and the microhardness of the coating surface can reach up to 1000 HV0.2,which is about 1.6 times of the substrate.The wear resistance of the Ni60 A coating is obviously better than that of the substrate,which is about 2.0 to 3.3 times higher than that of the substrate.After laser cladding of the multi-layer Ni-based alloy coating on the Cr12 MoV die steel surface,hard phases such as Cr3C2 and Ni-Cr-Fe can be formed and effectively improve the surface hardness and wear resistance.The probability of scrapping due to friction and wear can be significantly reduced,thereby further extending the service life of the mold.