| 摘要 |
PURPOSE:To enhance the oxidation resistance of a heavy alloy such as W-7Ni- 3Fe at high temp. in the air and to increase the surface hardness by simultaneously diffusing Cr and Si in the alloy and carrying out nitriding. CONSTITUTION:Fine W powder is mixed with fine powder of carbonyl nickel and carbonyl iron or carbonyl copper, and the mixture is molded and sintered to obtain a sintered body of a heavy alloy consisting of 90wt% W and the balance Ni and Fe or Cu. The sintered body is planed to about 5mum Ra surface roughness, and Cr and Si are diffused by a powder diffusion method. Powder for the diffusion consists essentially of about 60% Cr powder, about 20% Si powder, about 20% Al2O3 powder and about 0.5% NH4Cl, and it is diffused at about 1,200 deg.C in vacuum. The sintered body is then heated at about 1,100 deg.C for about 2hr in a flow of gaseous N2 contg. gaseous NH3 to nitride the surface. |
