Characterization of functional gradient structures in duplex stainless steel castings/Funktsionaalse gradientstruktuuri formeerumine roostekindlast dupleksterasest valanditel

Titanium carbide particle reinforced metal-matrix composite coatings, formed on duplex (austenitic/ferritic) stainless steel castings, were studied. These coatings, developed for wear applications, develop a functional gradient structure through a self-propagating high-temperature synthesis (SHS) of titanium carbide (TiC). This SHS-reaction was ignited in reactive inserts by the heat of liquid steel. The reactive inserts were compressed from mixtures of titanium, carbon and molybdenum powders together with iron or duplex stainless steel powders. The coating microstructure depends on the reactive insert composition. Molybdenum reduced the TiC particle diameter, and reducing the binder content reduced the areal fraction of TiC. Key words: particle reinforced cast structure, SHS-reaction, metal-matrix composite, coating, TiC, duplex stainless steel, interface. On uuritud titaankarbiidiosakestega tugevdatud metallmaatfkskomposiitidest pinnete formeerumist roostekindlast (austeniit/ferriit) dupleksterasest valanditel. Kulumiskindel, funktsionaalse gradientstruktuuriga metallmaatrikspinnete karbiidne (TiC) faas moodustus iseleviva korgtemperatuursunteesi toimel. Suntees kaivitus valuterase Urge temperatuuri (1650°C) toimel. Paksude gradientpinnete saamiseks valanditel vormiti valuvormi viimiseks sisetukid titaani, susiniku, molubdeeni ja komposiitpindes sideainetena kasutatavate raua- voi roostekindlast dupleksterasest pulbrite baasil. Saadud gradientstruktuuriga pinnete mikrostruktuur soltub lahtematerjalide koostisest. Naiteks molubdeen vahendab markimisvaarselt titaankarbiidiosakeste suurust pindes. Rauast voi dupleksterasest sideaine koguse vahendamine valuvormi sisetukis pohjustab tugevdava titaankarbiidi mahulise osakaalu vahenemist saadavas gradientpindes.