Microstructure and Thermal Properties of Laser Cladding Ni-Cr-Mo Alloy Steel Coating
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摘要: 用Nd3+:YAG激光器在H13钢基体表面上激光熔覆两种Ni-Mo-Cr系涂层,化学成分(质量分数,w/%)分别为Ni9Mo2Cr2.5Al0.15Ti1B4Si3Fe78.4和Ni2Mo2Cr2.5Al0.1Ti1B4Si3Fe85.4,分别用X射线衍射(XRD)、金相显微镜、扫描电镜(SEM)、能谱仪(EDS)及高温管式电炉对涂层的表面形貌、物相成分、微观组织、成分分布及热稳定性能进行研究。结果表明:两种Ni-Mo-Cr系粉末与基体皆可发生冶金结合,表面呈均匀的鱼鳞状,组织均匀致密,涂层主要物相为γ-(Fe,Ni)固溶体、FeCr、α-Fe和NiCrFe相等化合物,并且熔覆区组织为等轴晶,结合区组织为垂直于结合面且较为粗大的柱状枝晶。Ni添加量为9%和2%时的Ni-Mo-Cr系涂层平均显微硬度(HV0.2)分别为650和740,约为基体硬度(230)的2.8~3.2倍;两种Ni-Mo-Cr涂层的热稳定性能相对于H13钢都有很大提高,其中Ni添加量为2%时的涂层较佳。Abstract: in this paper,two kinds of Ni-Mo-Cr coatings were laser-clad on the surface of H13 steel substrate by Nd3+:YAG laser.The chemical compositions of applied coatings were Ni9Mo2Cr2.5Al0.15Ti1B4Si3Fe78.4 and Ni2Mo2Cr2.5Al0.1Ti1B4Si3Fe85.4(mass fraction,w/%)respectively. Surface morphology,microstructure,phase composition,composition and thermal stability of the coating had been investigated by X-ray diffraction(XRD),metallographic microscope,scanning electron microscope(SEM),energy dispersive spectroscopy(EDS) and microhardness tester.The results show that the coatings of two Ni-Mo-Cr powders are metallurgically bonded to the matrix.The surface morphology presents uniform and dense fish scale.The main phases of the coating are γ-(Fe,Ni) solid solution,FeCr,α-Fe and NiCrFe equivalent compounds.Tthe coating region is composed of equiaxed grain,and the bonding region is composed of relatively coarse,columnar dendrites perpendicular to the bonding surface.The average microhardness of Ni-Mo-Cr coatings with 9% and 2% Ni addition are 650 HV0.2 and 740 HV0.2,respectively,which is about 2.8 to 3.2 times that of the matrix(230 HV0.2). The thermal stability of the Ni-Mo-Cr coating is greatly improved compared to the H13 steel,and the coating is better when the Ni addition is 2%.
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Key words:
- H13 /
- Ni-Mo-Cr coating /
- laser cladding /
- microstructure /
- hardness /
- thermal stability
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