A pump assembly has a housing formed of at least two metallic housing parts (2) and at least one diffuser (12) arranged in the housing, wherein the diffuser (12) is fixed between the two housing parts in the axial direction, and the two housing parts (2) are directly or indirectly in metallic contact with one another, in a manner such that a force transmission in the axial direction between the housing parts (2) is effected via elements of metal.