METHOD OF TREATMENT OF FERROUS METAL PARTS SO AS TO INCREASE THEIR RESISTANCE TO WEAR AND SEIZURE

摘要

1424136 Modifying ferrous metal surface CENTRE STEPHANOIS DE RECHERCHES MECANIQUES HYDROMECANIQUE ET FROTTEMENT 16 Feb 1973 [18 Feb 1972 29 Nov 1972 23 Jan 1973] 7776/73 Heading C7U Ferrous machine parts are treated to form thereon a white microlayer of at least nitrides and carbides by immersion (e.g. for 30 to 60 minutes) in a molten salt bath at 450-600‹C containing 1-35 wt per cent of carbonate ions, 20-65 wt per cent of cyanate ions, potassium ions, sodium ions and lithium ions the ratio of Li:Na by weight being 0À15 to 0À5 and Li: K being 0À1 to 0À35. The bath may comprise 4 to 6% lithium, SSP2-/SP, SO 3 SP--/SP, S 2 O 3 SP--/SP and PO 3 SP--/SP ions and may be regenerated using urea which is introduced from a distributing device 9 via a hermetically sealed conduit 5 by a gas (e.g. air) from compressor 27. The conduit 5 being surrounded by a cooling jacket 19 through which a cooling gas (e.g. air) is passed. The regenerating agent may be contacted initially with the molten salt in the region of a diffuser 2 and the gases produced allowed to stir the melt and escape via outlet 24.