GB661031A - Improvements in parts for jet propulsion engines and their manufacture - Google Patents

Abstract

A jet-propulsion engine part comprises a sintered ferrous body infiltrated with copper or copper alloy with a continuous coating of zinc, tin, zinc alloy or tin alloy. In making a compressor blade, ferrous metal particles of 80 to 325 mesh are briquetted at 6-50 tons/sq. inch to form a blank with 10-30 per cent porosity by weight. The metal may be pure iron or contain up to 1 per cent carbon or a proportion of steel or alloy steel. If the porosity exceeds 15 per cent it may be presintered, e.g. if iron at 900 DEG -1100 DEG C. for 30 minutes before compression to reduce the porosity. The briquette is then impregnated with copper by heating it in contact with a weighed amount of copper in a clean dry protective atmosphere at 1125 DEG -1250 DEG C. for 10-15 minutes. The copper is preferably alloyed with 5 per cent manganese and 1 per cent silicon or 2-8 per cent manganese and 1-2 per cent iron. 0.2 to 5 per nickel, titanium, phosphorus, chromium and/or sulphur may be added instead of, or in addition to, manganese, silicon and iron. The impregnated blank may be heat-treated to alloy the metals superficially. It is then dipped in a bath of tin or zinc at about 800 DEG C. causing the coating to alloy with the matrix metal to a depth of 0.003-0.004 inch. To the zinc bath may be added from 1 to 30 per cent by weight of copper. Aluminium and/or tin may also be added in addition to, or instead of, the copper. To the tin bath, up to 10 per cent copper may be added. The bath is covered with cryolite or alternatively protected by dry hydrogen or carbon dioxide, or a flux of zinc, potassium, or sodium chloride. The coated blade then undergoes heat treatment at 350 DEG -380 DEG C. for a zinc coating or 200 DEG C. for a tin coating. Heat treatment may be carried out in air to form a dense oxide cover on the coating. Instead of dipping, the blade may be packed in powdered zinc or zinc alloy and heated for 3-4 hours at 350 DEG -485 DEG C. or in powdered tin or tin alloy at 200 DEG -280 DEG C. A further diffusion treatment may follow. Again, the coating may be applied by electroplating followed by diffusion treatment at 350 DEG -485 DEG C. for a zinc alloy coating. Specification 644,907 is referred to. The Specification as open to inspection under Sect. 91 states that aluminium may be added to the tin bath, and that the coating may be applied by anodizing. This subject-matter does not appear in the Specification as accepted.