Movable wall member in form of an exhaust valve spindle or a piston for internal combustion engine, and a method of manufacturing such a member

A method of manufacturing a movable wall member in form of an exhaust valve spindle or a piston for an internal combustion engine, comprising the following steps:

• providing a base portion of the moveable wall member, which base portion comprises an alloyed steel having a carbon-content in the range from 0.15 to 0.35% by weight,
• providing an outer portion, which outer portion is of a hot-corrosion-resistant alloy, which is nickel-based, chromium-based or cobalt-based,
• placing a buffer layer on the base portion and then placing the outer portion on the buffer layer, which buffer layer is of an alloy comprising from 0% to at the most 0.09% C in percent by weight of the buffer layer and having an alloy composition different from the alloyed steel of the base portion and different from the hot-corrosion-resistant ally of the outer portion, said base portion, buffer layer and outer portion being unified to a coherent wall member with the buffer layer located in between the base portion of alloyed steel and the outer portion, in which wall member the buffer layer prevents diffusion of carbon from the alloyed steel of the base portion to the hot-corrosion-resistant alloy of the outer portion.