As refractory metal,niobium has been used in aerospace industry.Niobium tungsten alloy with high strength at high temperatures and at room temperature and has good plasticity, available conventional forming technology made into all kinds of processed materials and parts, used in the shuttle's skin, nuclear reactor engineering, jet engine parts and space power generation system thermal radiation panel and tubes, etc. Niobium tungsten alloy is used in the related supporting facilities of chang 'e 3.The new niobium tungsten alloy developed by ningxia dongtantalum industry has been successfully applied to the "xinno 6" and "moonshot engineering". Niobium tungsten alloy destructive oxidation happens in high temperature aerobic environment, need through the alloying coating modification and coating protection,high temperature but alloying modification will seriously affect the mechanical properties, so the alloy coating on the surface of the coating protection become a research focus,surface coating of high temperature oxidation resistance directly determines the shuttle engines with niobium tungsten alloy working temperature. The silicified coating was prepared with the preparation of niobium tungsten alloy with niobium tungsten alloy. They developed the niobium tungsten alloy Nb521-1, the main component is 5w-2mo - 1Zr, the rest is Nb. Coating preparation process is as follows: Si, Ti, Cr powder mixed in certain proportion,add a certain amount of organic solvent, load the corundum tank, the use of ball mill mixing and drum rotational speed, 200-300 r/min, corundum ball 5 -- 10 mm in diameter, the ball material volume ratio 1:1, ball grinding time 24 h,after mixing viscous suspension slurry system.Slurry evenly coated in niobium tungsten alloy base material surface, placed in a vacuum sintering furnace in 1320-1320 degrees in the heat preservation 18 to 40 min, repeat the above operation after a coating sintering for secondary coating sintering, coating. They found that the alloy coating will appear in the process of preparation and use of coating accumulation,stacking area coating surface is obviously different from other normal region, accumulation of a bit accumulation and line two kinds of surface defects. The coated slurry is mixed with coating material, and the coating material is deposited on the coated surface of the coating. In the process of melting, when the coating appears to fall off, the shedding area exceeds the self-leveling ability of the remaining slurry, which will generate the line accumulation and the surface defects associated with the leakage.The comparison of the spectra of the coating in normal region and accumulation area shows that there is no significant difference between the composition of the coating area and the composition of the normal coating. The accumulation coating is consistent with normal coating structure,consisting mainly of outer layer,main layer and diffusion layer.Normal coating thickness is 120 microns, point accumulation coating thickness is 120 microns, and line stacking area coating thickness fluctuation is bigger, thicker coating area and other area of about 50 microns thickness difference.Accumulation is coated particles embedded has a little influence on the coating surface and the cross section,and line accumulation is superposition of slurry in the process of coating preparation,although does not affect the structure of the coating, but has a great influence on the thickness of the coating area. Static antioxidant 1800 degrees and 1600 degrees thermal cycle life of contrast test showed that the accumulation point coating with normal coating were similar,which means that under the condition of the experiment,accumulated points won't cause bad influence on coating performance;But line accumulation generally have a coated surface defects such as leakage, associated test and high temperature, when the workpiece surface is leaking area, the workpiece substrate directly exposed in the air, will inevitably lead to artifacts in leakage besmear in rapid failure.Therefore, the effect of line accumulation on coating performance can only be removed by refilling the leakage area. for more details,just visit our website www.wococarbide.com

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