Abstract: A backflow blocking arrangement is for an injection unit of an injection molding machine having a plasticising screw with a front end for carrying the backflow blocking arrangement. The arrangement has a screw tip, a blocking bush and a blocking sleeve each with a base body material. The screw tip has friction surfaces and the blocking bush and the blocking sleeve each have sealing and friction surfaces. At least one of the friction and sealing surfaces is formed by a protective layer made of a fusion metallurgical compound of the base body material plus an additive. The additive is any one or more of a metal, a carbide, a carbonitride, a boride, a carboboride, a silicide, a sulfide or an oxide. The screw tip includes a mixed layer between its base body material and its outer layer, that includes the additive. The mixed layer is thinner than the outer layer and both the outer layer and the mixed layer include base body material in specific proportions with the additive.