W-Mo-Si/SiC Oxidation Protective Coating for Carbon/Carbon Composites

A W-Mo-Si/SiC double-layer oxidation protective coating for carbon/carbon （C/C） composites was prepared by a two-step pack cementation technique.XRD （X-ray diffraction） and SEM （scanning electron microscopy） results show that the coating obtained by the first step pack cementation was a thin inner buffer layer of SiC with some cracks and pores,and a new phase of (W;Mo;)Si;appeared after the second step pack cementation.Oxidation test shows that,after oxidation in air at 1773 K for 175 h and thermal cycling between 1773 K and room temperature for 18 times,the weight loss of the W-Mo-Si/SiC coated C/C composites was only 2.06%.The oxidation protective failure of the W-Mo-Si/SiC coating was attributed to the formation of some penetrable cracks in the coating.