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Quality Investigation of Ir-PyC-SiC Coating System

Author: YangWenBin
Tutor: ZhangLiTong；ChengLaiFei
School: Northwestern Polytechnical University
Course: Materials Processing Engineering
Keywords: Metal-organic chemical vapor deposition Iridium coating High temperature treatment Failure mechanisms
CLC: TG174.4
Type: Master's thesis
Year: 2005
Downloads: 130
Quote: 2
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Abstract


Has excellent high temperature oxidation resistance , Ir Ir - Re system liquid rocket engine nozzle has achieved initial application , but the rapid diffusion of Re in the Ir cause nozzle failure . In this paper, the IR - PYC- SiC composite coatings for C / SiC oxidation solution , using SEM, XRD and EDS analysis tools , coating microstructure and composition analysis to explore the factors influencing the quality of the composite coatings PyC effect of the reaction barrier layer , and evaluation of practicability of the system was made ??. The main findings are as follows : (1) IR coating microstructure obtained metal-organic chemical vapor deposition process parameters on the quality of the law: the precursor source and the sample spacing IR coating density and defect density . With spacing from 250mm to 450mm in constituting the coating layer of Ir particle size decreased from 50nm to 20nm, to improve the density of coating , the defect density decreases ; roughness of the surface of the substrate has a greater impact on the Ir layer defect density . The rougher substrate , holes and cracks and other defects of the coating more intensive bigger size . Defects low priority in the substrate recessed portion generated ; coating deposition efficiency increases with increasing deposition temperature , approximately when 500 ° C is 5 times the thickness of the resulting coating at 600 ° C deposition . ( 2 ) the use of acoustic emission scratch test the IR Coating Adhesion . Reveal the PyC lamellar structure is lead to a the Ir coating with the substrate mainly due to weak binding , and the PyC layer has a thickness from 100nm to 400nm corresponding Ir coating bonding force reduced by 18N to 8N . The PyC layer thin the SiC coating cracks , and sharp edges and corners , not fully block the IR and SiC contact . (3 ) heat treatment experiments show that the high temperature stability of the IR - PYC- SiC composite coatings is poor . The inert atmosphere is short ( 5 min ) 1450 ° C following heat treatment , coating and substrate thermal mismatch caused by the Ir coating macroscopic crack ; MOCVD Ir coating nanocrystals , low thermal stability , the sintering shrinkage generated a large number of micro-cracks and holes ; , Ir coating in the SiC coating cracks consumed by the SiC reaction , the reaction product of Ir 3 < / sub > Si ( 1345 ° C ) boiling in large part to accelerate the process of coating failure . With the heat treatment temperature and time extended , Ir coating overall VALID specimen surface without elemental Ir remaining after the heat treatment , the reaction product IrSi and Ir to the 3 < / sub > Si .

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metal corrosion protection,metal surface treatment > Corrosion control and protection > Metal surface protection technology
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