Screw for an extruder and extruder device

An extruder device for extruding a material, comprising:

• a plurality of components, each having a metal body coated by an external functionalization coating (4) wherein at least one of said components which, during extrusion, is brought into contact with said material to be extruded, is at least partially coated by a wear detection-quantification coating (5) arranged between the body of said component and the corresponding external functionalization coating (4), and wherein a chosen color of said wear detection-quantification coating (5) is visually distinguishable from a color of said external functionalization coating (4) to identify wear without the use of a measuring apparatus or an analyzing process,
• wherein the external functionalization coating (4) is in a material which is compatible, from the point of view of the chemical and physical interactions, with the extruding material and with the end use of the same,
• wherein the wear detection-quantification coating (5) is made of a material selected among filler materials, nitrides, carbides, carbonitrides, crystalline materials, and diamond,
• wherein the wear detection-quantification coating (5) has a hardness greater than 1500 HV, and
• wherein the wear detection-quantification coating (5) comprises at least two wear detection layers, with each wear detection layer being of a color different from other wear detection layer(s) thereof to thereby determine an amount of wear detection-quantification coating lost during extrusion.