NEEDLE VALVE

PURPOSE:To provide a needle valve which has the same degree or more of anti-corrosiveness and wear resistance against earth and sand as stainless steel in an environment involving a weak acid water by applying a composite weld fillet covering layer on a parent material of austenite series stainless steel to form a nozzle and a needle. CONSTITUTION:A needle valve to be installed in a vertical shaft Pelton hydraulic wheel for hydraulic power generation is equipped with a needle 4 and nozzle 3 formed from an Fe-based base material of ferrite/pearlite series or martensite series, and an anti-abrasive covering layer is applied to the mating surfaces of the needle 4 and nozzle 3 to touch the fluid 15. The covering layer consists of a composite weld fillet covering layer at least on the mating surfaces 14 as a mixture powder containing 3-6wt.% silicon carbide SiC as ceramics of carbide series and an austenite type alloy and also an intermediate fillet layer as a buffer containing powder of austenite alloy having a greater coefficient of thermal expansion than the base material and a composite weld fillet covering between the mentioned composite weld fillet covering layer and base material.