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Microstructure And Properties Of Ni60A+Ceramics Laser Cladding Layer

Posted on:2016-03-26Degree:MasterType:Thesis
Country:ChinaCandidate:J Q ShiFull Text:PDF
GTID:2191330461492646Subject:Materials engineering
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In the industrial field, the partial surface of many machines that are working under conditions of high temperature, high speed, high friction and the corrosive medium, are often easily damaged. And the damage on the surface can easily cause the failure of the entire equipment. Therefore, it is useful that using laser cladding technology to improve the surface properties of the material. In this paper, Ni60A, Ni60A+Fe450, Ni60A+Fe450+Mo, and Ni60A+WC+Fe450cladding layers were made on surface of Q345 steel. The laser cladding layer’s micro-structure, phase composition, and the wear and corrosion resistance are discussed in this paper.Semiconductor lasers equipment is used in the experiment, and the best process parameters to obtain the best forming quality and dilution rate is as follows: rectangular beam spot size of 14mm×2mm, laser power is 2.8 kw, scanning speed of 300~600mm/min, multi-channel cladding lap was 50%, using the argon as the laser side-blown protection.The main component of nickel-based cladding layer is y-(Ni,Fe,Cr), and with the adding of Fe450, the Austenite matrix becomes γ-(Fe, Cr, Ni, C). The nickel-based cladding layer also contains FeNi3, BNi3, CrB, Cr3B5, Cr23C6. With the increase of Fe, Cr, new phases, such as FeCr, Fe3B, CrFeB and Fe3Ni3B, are formed. Beside, many Cr23C6 turns into Cr7C3 and Cr3C2.With the addition of WC, W2C, CW3, FeW2B2 are formed in the cladding layers. Additionally, The cladding layers with Mo inside have Cr2Fe6.7Mo0.1Nii.3Si0.3, CrFe3.2MoNi and (Fe,Ni,Mo)23B6.There are columnar crystals and equiaxed grains, as well as flower-shaped Cr-rich phase in the Ni-based cladding layers. With the addition of Fe450, Cr-rich phase becomes smaller. If continuing increasing Fe450 to 30-40wt%, the cladding layer are mainly contains large austenite dendrites. In the Ni60A+Fe450+Mo cladding layers, with the Mo content increasing, short equiaxed dendrite decreased, instead fish bone shaped organizations and feathery shaped structure appeared. In Ni60A+WC+Fe450 cladding layers, with the increase of Fe450 content, the square phase rich in W and Cr gradually become blocks with four acute angle, and began to gather together. So the addition of Fe450 changes the shape of secondary phase in the laser cladding layer.Fe450 can effectively improve the hardness, wear resistance and high temperature acid corrosion of Ni-based cladding layers. The addition of Mo in Ni60A+Fe450 cladding layers can improve the hardness, though the wear resistance is lower than cladding layers without adding Mo elements, it is still better than pure Ni60A wear cladding layer. In addition, Mo can also improve the corrosion resistance of the cladding layer, and the optimal chloride corrosion-resistant ability and acid corrosion resistance ability of cladding layers with Mo is 5 times and 1.3 times as many as Ni60A respectively.In Ni60A+WC+Fe450 laser cladding layers, the best combination is adding 7wt% Fe450(B2). The wear resistance of B2 is 8 times as many as Q345, and is 3 times as many as the abrasion resistance of pure Ni60A cladding, only slightly inferior to Ni60A+WC cladding layer. Besides, the cladding layer under this formula also has excellent resistance to chloride corrosion and high temperature acid. The acid resistance of B2 is 6 times as many as the pure Ni60A layer, twice as many as Ni60A+WC layer,12 times as many as the Q345 substrate.
Keywords/Search Tags:laser cladding, ceramic particles, micro-structure, wear resistance, corrosion resistance
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