Investigation of the Multi-coating for High Temperature and Long Life Oxidation Protection of C/C Composites

A SiC-WSi_2/MoSi_2 multilayer oxidation protective coating for carbon/carbon(C/C)com- posites was prepared by pack cementation.Effects of the total content of W and Mo on the microstruc- ture and high temperature anti-oxidation property of the multi-coating were studied by XRD,SEM, EDS and isothermal oxidation test.The results show that with the total content of W and Mo increas- ing in the pack powders,the as-received multi-coating thickness first increases and then decreases.The multi-coating with 10.0at%(W and Mo)has a thicker,denser structure and higher content of WSi_2 and MoSi_2 than those with 0at%,8.4at% and 13.1at%(W and Mo).A stable and dense glassy SiO_2 film can be formed on the coating surface with 10.0at%(W and Mo)during the oxidation test.The coated specimen with 10.0at%(W and Mo)has no weight loss after oxidation in air for 315h at 1500℃and no cracks after thermal cycling between 1500℃and room temperature for 18 times,which implies that the multi-coating has excellent oxidation protective ability and thermal shock resistance.