Chitsulo chokhazikika cha mpira chokhala ndi kaboni ndi chromium chinasankhidwa ndikuumitsidwa kuti chipirire kupsinjika kwakukulu pakati pa chinthu chogudubuza ndi mphete zonyamulira.
Carbonitriding pa mphete zamkati ndi zakunja ndi njira yolimbikitsira kwa ogulitsa ambiri a TPI mpira. Kupyolera mu chithandizo chapadera cha kutentha kumeneku, kuuma pamtunda wothamanga kumawonjezeka; zomwe zimachepetsa kuvala moyenera.
Chitsulo choyera kwambiri chikupezeka muzinthu zina zamtundu wa TPI wamtundu wa mpira tsopano, kukana kwapamwamba kumapezedwa moyenerera. Popeza kutopa kukhudzana nthawi zambiri kumabwera chifukwa cha zolimba zopanda zitsulo, mayendedwe masiku ano amafunikira ukhondo wapadera.