Hoʻohālikelike ʻia ka hui kemika o martensitic kuhiliʻole kila e ka hoʻohui o nā mea e like me molybdenum, tungsten, vanadium, a me niobium ma ke kumu o nā hui like ʻole o 0.1% -1.0% C a me 12% -27% Cr. Ma muli o ka hoʻonohonoho hoʻonohonoho ʻana he kino cubic centered-kino, hāʻule nui ka ikaika i nā mahana wela. Ma lalo o 600 ℃, ʻo ka ikaika o ka mahana wela ka mea kiʻekiʻe ma waena o nā ʻano o nā kila kila, a ʻo ka ikaika kolo ka mea kiʻekiʻe loa hoʻi. ʻO ka 440A kila ke kinai maikaʻi a me ka hana paʻakikī, kiʻekiʻe paʻakikī, a ʻoi aku ka paʻakikī ma mua o 440B kila a me 440C kila. Hoʻohana ʻia ka kila 440B no ka ʻoki ʻana i nā pono hana, ke ana ʻana i nā pono hana, nā bearings a me nā valves. 440B kila ʻoi aku ka paʻakikī ma mua o 440A kila a ʻoi aku ka paʻakikī ma mua o 440C kila. ʻO ka 440C kila ka paʻakikī ʻoi loa ma waena o nā mea kila kila a me nā mea pale wela, a hoʻohana ʻia no nā nozzles a me nā bearings.