A process for the welding of two polyamide parts, both made of a polyamide composition comprising a polyamide and optionally additives, the polyamide of one part (part L) having a lower softening temperature than the polyamide of the other part (part H), and wherein the polyamide composition of part L comprises one or more viscosity increasing additives increasing the melt shear viscosity of the polyamide composition at least by 30% compared to melt shear viscosity of the polyamide (measured according to ISO 11443 (A1) standard at a shear rate of 100 s.sup.-1 in a capillary rheometer with I/d =30 mm/1 mm). A good weld strength is obtained and parts with different properties can be combined. Polyamide welded objects such as corrugated tubes, bellows, containers, fuel inlet systems, air inlet manifolds and airducts, may be obtained.