摘要
在N2−H2−BCl3气氛下对镍硅合金进行两级气体渗硼(910℃、2 h)制备双区硼化层。显微组织由两种具有不同相成分的区域组成。外层区域仅含有硼化镍的混合物(Ni_(2)B,Ni_(3)B),内层区域除了硼化镍还含有硅化镍(Ni_(2)Si,Ni_(3)Si)。研究硅化镍的存在对镍基合金表面硼化层力学性能的影响。使用带有Berkovich金刚石压头的纳米压痕仪在50 mN载荷下测量硬度和弹性模量。结果显示,外层区域的平均压痕硬度和压痕弹性模量值分别为(16.32±1.03)GPa和(232±16.15)GPa。内层区域中硅化镍的存在降低其压痕硬度(6.8~12.54 GPa)和弹性模量(111.79~153.99 GPa)。采用维氏微压痕法研究硼化层在0.981 N载荷下的断裂韧性。结果表明,硅化镍的存在使气体渗硼层的脆性增加(约40%)。
The two-stage gas boriding in N_(2)−H_(2)−BCl_(3)atmosphere was applied to producing a two-zoned borided layer on Nisil-alloy.The process was carried out at 910℃ for 2 h.The microstructure consisted of two zones differing in their phase composition.The outer layer contained only a mixture of nickel borides(Ni_(2)B,Ni_(3)B)only.The inner zone contained additionally nickel silicides(Ni_(2)Si,Ni_(3)Si)occurring together with nickel borides.The aim of this study was to determine the presence of nickel silicides on the mechanical properties of the borided layer produced on Ni-based alloy.The hardness and elastic modulus were measured using the nanoindenter with a Berkovich diamond tip under a load of 50 mN.The average values of indentation hardness(HI)and indentation elastic modulus(E_(I))obtained in the outer zone were respectively(16.32±1.03)GPa and(232±16.15)GPa.The presence of nickel silicides in the inner zone reduced the indentation hardness(6.8−12.54 GPa)and elastic modulus(111.79−153.99 GPa).The fracture toughness of the boride layers was investigated using a Vickers microindentation under a load of 0.981 N.It was confirmed that the presence of nickel silicides caused an increase in brittleness(by about 40%)of the gas-borided layer.
基金
This work has been financially supported by Ministry of Science and Higher Education in Poland as a part of the Project No.0513/SBAD.
关键词
气体渗硼
硬度
弹性模量
纳米压痕
断裂韧性
gas boriding
hardness
elastic modulus
nanoindentation
fracture toughness
