Improvement in thermal fatigue behavior of Si-Mo-Cr coated C/C composites through modification of the C/C-coating interface

Pre-oxidation is used as a treatment to carbon/carbon (C/C) composites for improving the thermal fatigue behavior of Si-Mo-Cr coated C/C composites. Si-Mo-Cr coating was prepared on C/C composites by pack cementation, and the thermal fatigue behavior of the coated samples was studied. After thermal cycling in air between 1773 K and room temperature for 15 times, the mass losses of the coated C/C substrate without and with pre-oxidation were 6.3% and 3.8% respectively. Also, percentages of the remaining flexural strength of the coated C/C substrate without and with pre-oxidation were 71.78% and 82.97%. The improvement of the thermal fatigue properties of the coated samples with pre-oxidation was mainly attributed to the formation of a transition interlocking structure at C/C-coating interface, which is advantageous in alleviating the CTE mismatch between Si-Mo-Cr coating and C/C substrate, decreasing the crack size in the coating.