The isothermal section of Nb-Ti-Co ternary system rich in Co and Ti at 1173 K was determined by means of diffusion triple and electron microprobe analysis.The results indicate that there are six binary intermediate compounds formed:NbCo3,NbCo2,TiCo3,TiCo2,TiCo and Ti2Co.In this diffusion triple,Nb and Ti formed continuous solid solution,and no ternary compound was formed.There are six three-phase regions found at this temperature:(Co)+TiCo3+NbCo3,NbCo3+TiCo3+NbCo2,NbCo2+TiCo3+TiCo2,TiCo2+NbCo2+TiCo,NbCo2+TiCo+Ti2Co and NbCo2+Ti2Co+(Nb,Ti).