Abstract: Normally closed valves that operate in the environment of nuclear power plants are provided with surface-modified valve seat components to alleviate sticking of the valves. The surface modification is achieved by ion implantation of a coating of, for example, platinum, palladium, platinum/palladium or palladium/gold on at least one valve seat component.

Abstract: A method of forming a stable welded joint between low alloy steels and austenitic stainless alloy steels which is characterized by increased resistance to chemical corrosion and mechanical stress and which has a greatly extended service lifetime. The method comprises forming a deposit of a low alloy steel containing niobium onto a portion of low alloy steel to be welded; heating the deposit to a first temperature at which all carbides present therein have dissolved; quenching the deposit and forming a solid solution of the elements of the dissolved carbides; and reheating the deposit for a time period and at a second temperature sufficient to form niobium carbides therein containing substantially all of the carbon present in the deposit. The austenitic stainless steel portion is welded to the deposit using a substantially nonferrous nickel-based alloy as the weld filler material, thereby joining the low alloy steel portion to the austenitic stainless steel portion.