The Study Of In Situ Synthesis Of ZrB₂-ZrC-B₄C-SiC High Temperature Ceramics Coating By Tig Cladding

Single-pass and multi-pass ceramic coatings were in-situ synthesized on carbon matrix by means of gas tungsten arc cladding, with Zr, B₄C, AlN andSiC powders as raw powder. Different series of Zr-B₄C-AlN and Zr-B₄C-AlN-Si were designed. The effect of cladding process paraments on microstructure and properties of the coating was studied. The interfacial bonding strength, micro-hardness and high temperature oxidation resistance of the coating were also examined.ZrB₂-ZrC-B₄C single-pass ceramic coating was got by using TIG cladding Zr-B₄C-AlN powder system, with polygonal bright white ZrB₂-ZrC phase distributingaround chunks B₄C phase. ZrB₂-ZrC-B₄C-SiCsingle-channel ceramic coating wasmade by Zr-B₄C-AlN-Si powder system, a small piece of ZrB₂-ZrC distributingaround the alternating strips B₄C-SiC. The microstructure and phase formation ofmulti-pass ZrB₂-ZrC-B₄C-SiCcladding was similar with single-pass coating. But inthe overlap junction region ZrB₂-ZrC phase gathers together.The bonding strength between sigle-pass ceramic coating and carbon substrateis tested, with the result showing that there is a stronger bonding between thecoating and substrate than the substrate. So the coating and the substrate achieve agood metallurgical bond.The microhardness of the coating is unevenly distributed, mainly associatingwith the refinement of organization and aggregated distribution of the ZrB₂-ZrCphase. The flowing of weld pool makes ZrB₂-ZrC moving to the surface and the thecenter of coating, which leading to a higher hardnes at the center and the surface ofthe coating.At temperature of1200℃, the quality of ZrB₂-ZrC-B₄C single-pass ceramiccoating reduces gradually which indicating low anti-oxidant capacity. The qualityof the ZrB₂-ZrC-B₄C-SiCsingle-pass ceramic coating firstly decreases and thenholds a constant which showing a strong oxidation resistance. As a whole, the ZrB₂-ZrC-B₄C-SiC multi-pass ceramic coating has a certain resistance to oxidation, butat the junction of the overlap region there exists microporous which weakening theantioxidant capacity.