PURPOSE: To obtain a sliding mechanism with superior wear resistance by forming one sliding member with an Fe alloy having a specified composition and the other sliding member with an Ni alloy having a speicified composition and by specifying the difference in hardness between both the alloys.

CONSTITUTION: A pin for guiding a fuel control rod for a nuclear reactor is formed with an Fe alloy consisting of ≤0.3% C, 7W40% Ni, 15W28% Cr, 2W8% Si, 3W12% Mn and the balance Fe and having ≥ about 300 Vickers hardness and an austenite-base structure. A roller for guiding the rod is formed with an Ni alloy conisting of ≤0.5% C, ≤2% Si, ≤2% Mn, 13W22% Cr, 3W10% Mo, ≤10% at least one of Ti and Al, and the balance Ni and having ≥ about 450 Vickers hardness and a structure contg. γ' phase precipitated in the austenite phase matrix. The difference in Vickers hardness between the contact surfaces of both the members is adjusted to ≤200.