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Study On The Effect Of Rare Earth Elements On The Properties Of TB2 Titanium Alloy Boronized Layer

Posted on:2019-08-14Degree:MasterType:Thesis
Country:ChinaCandidate:L S MaFull Text:PDF
GTID:2431330563458031Subject:Materials engineering
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Due to good mechanical properties and mechanical properties,such as high fracture toughness and aging strength,high specific strength,and good cold forming,titanium and titanium alloy materials have important applications in aerospace and other important fields,which the direction of technological development.However,some inherent defects of titanium and titanium alloy materials restrict its further application,such as low hardness?nano-hardness of titanium and titanium alloys is 2-3GPa?,poor wear resistance,poor thermal conductivity,and easy seizure.Titanium and titanium alloy materials are chemically active,and the oxide film on the surface can play a protective role,but the surface oxide film is very thin.If it is damaged or crevice corrosion occurs,its corrosion resistance will be greatly reduced.In order to improve the comprehensive performance of titanium and titanium alloy materials,surface treatment and modification of the matrix material has become a new research hotspot in this field.In this paper,the surface modification of TB2 titanium alloy was carried out by solid boriding and complex boronization with rare earths.X-ray diffractometer,scanning electron microscope,electron probe,nanoindentation instrument,micro-scratch tester and micro-vibration friction and wear tester were used to analyze the comprehensive performance of mono-bored boron and composite boronized samples.The results are as follows:The boronized layer consists of a Ti B2 phase and a secondary Ti B whisker phase.The boronization temperature is 950°C,1000°C,1050°C,1100°C for 5h,10h,20h,30h.The thickness of the boride layer is 11-33?m,and the nanohardness of the sample after boriding is also greatly improved,and the wear resistance and corrosion resistance are enhanced.However,the binding force between boride layer and the substrate is only 32N.Orthogonal test results show that the best process parameters for the addition of rare earth composite boronization are 1100°C-30h-Ce O2-10%.The experimental results of composite boronization with rare earth addition show that the addition of rare earth promotes the growth of Ti B whiskers,makes the boronized layer more dense,the friction coefficient decreases to 0.14,and the combination of composite boronization boriding layer and the substrate can reach 59N.The corrosion resistance of the composite boronization sample in H2SO4 and Na Cl solution was enhanced compared with that of boriding.The growth kinetics of the boriding layer is known to show that when the boriding temperature is lower?1000°C?,the Ti B whiskers grow faster,and when the temperature is higher?1050°C?,the Ti B2 layer grows.The boriding has a total diffusion coefficient of 10-15,and the diffusion rate is relatively small,which indicates that B atoms are difficult to diffuse in the TB2 matrix.
Keywords/Search Tags:TB2 type titanium alloy, boriding, rare earth, composite boronization, wear resistance and corrosion resistance
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