Mo2NiB2系硬質合金と各種鋼材との接合特性

概要

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Bonding properties of Mo2NiB2 base hard alloys with various steels were studied by using the model alloys whose compositions were Ni-4mass%B-42.6mass%Mo-17.5mass%Cr. The new hard alloys consist of a Mo2NiB2 type ternary boride as a hard phase and a nickel base binder alloyed with Cr, Mo and other elements, both of which are formed by reaction boronizing sintering. The hard alloys showed the shear strength of over 400MPa bonded with JIS S45C, SKD61, SCM 440, SUS42OJ2 at 1533K and that of over 700MPa with JIS SUS316L and SUS304 at 1503K. Surface roughness of the steels affected shear strength of the hard alloys bonded with JIS S45C, SKD 61, SCM440. Bonding time of 300sec was enough for high shear strength of the hard alloys bonded with various steels except JIS SKD61. The residual compressive stress in the hard alloys and residual tensile stress in the steels were measured by an X-ray diffraction stress analyzer. The results were attributed to the difference in the thermal expansion coefficient between the hard alloys and various steels.