Fracture Characterization of TiAl Matrix Composites by Addition of Fluoride Solid Lubricants

Abstract

The fracture characterization of Ti–48Al–2Nb-2Cr composites (TANC) with addition of different weight contents of fluoride solid lubricants (LiF, NaF, CaF2 and 38%CaF2-62%BaF2 eutectic solid lubricant (BC) ) were evaluated in the paper. The fracture toughness of composites with different content of fluoride solid lubricants is discussed. The TANC composites with 0-5 wt.% solid lubricant exhibit higher fracture toughness. It can be seen that additions of all fluoride solid lubricants to TANC matrix result in decrease in fracture toughness expect for additions of 5% of that. By adding 5 wt.% BC the fracture toughness of the TANC composites exhibited a maximum value of 12.2MPa m1/2; by addition of 5%CaF2, 11.4 MPa m1/2; 5%LiF, 10.8 MPa m1/2 while 5%NaF, 11.1 MPa m1/2. However, with further increasing of fluoride solid lubricants contents it showed a downward trend. By adding 20 wt.% BC the fracture toughness of the TANC composites exhibited a maximum value of 8.6 MPa m1/2; by addition of 20%CaF2, 8.1 MPa m1/2; 20%LiF, 8.3 MPa m1/2 while 5%NaF, 7.9 MPa m1/2.