La_2O_3强化等离子喷焊镍包铝涂层的组织及高温耐磨性能
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摘要
加入稀土氧化物可改善喷焊层的组织结构,提高涂层硬度。采用等离子喷焊工艺在20钢表面制备不同添加量La_2O_3的镍包铝合金喷焊层。通过光学显微镜、SEM、能谱仪、X射线衍射仪、显微硬度、热震试验以及高温摩擦磨损试验,研究了La_2O_3对喷焊层组织结构与性能的影响。结果表明:镍包铝等离子喷焊层显微组织的主体形态为树枝晶,树枝晶内部为α-(Fe,Ni)板条马氏体群,晶间网状组织为γ-(Fe,Ni);这种组织结构使镍包铝等离子喷焊层在750℃仍保持较好的抗热震性;添加0.5%La_2O_3后镍包铝喷焊层硬度提高了19.4%,但对喷焊层抗热震性能无明显改善;镍包铝喷焊层在500℃时的高温摩擦磨损试验中表现出较好的摩擦稳定性和理想的高温耐磨性能,这是因为其组织结构中存在韧性较好的晶间γ-(Fe,Ni)组织,呈网状包裹着强硬度较高的α-(Fe,Ni)板条马氏体,因而不易在磨损时发生剥离现象。添加0.5%La_2O_3可使其高温耐磨性能达到最佳;当La_2O_3添加量达1.0%时,镍包铝等离子喷焊合金层的硬度、抗热震性能以及高温耐磨性能较0.5%添加量时有所下降。
Adding rare-earth oxides could improve the structure and hardness of sprayed welding coatings. The sprayed nickel-coated aluminum coatings with adding different La_2O_3 contents were prepared on the surface of 20 steel by plasma spray welding. The microstructure and performance of coatings were studied by optical microscopy,SEM,EDS,X-ray diffractometer,micro-hardness tester,thermal shock test and high-temperature wear test. Results showed that the microstructures of nickel-coated aluminum plasma sprayed layer were dendrites,and the dendrites were some lath α-( Fe,Ni) martensite groups with intergranular reticular phase of γ-( Fe,Ni). These structures endowed the nickel-coated aluminum plasma sprayed coatings with good resistance of thermal shock at 750 ℃. The addition of 0.5% La_2O_3 improved the hardness of the nickel-coated aluminum plasma sprayed layer by 19.4%,but did not have obvious effect on the resistance of thermal shock. In addition,nickel-coated aluminum spray welding coating showed a good friction stability and ideal-high temperature wear resistance in high-temperature friction and wear tests at 500 ℃,which resulted from that the tissue structure possessed the γ-( Fe,Ni) intercrystalline tissues with good toughness and high-strength latitudinarian α-( Fe,Ni) slabs. When 0.5% La_2O_3 was added,the high-temperature wear-resistant performance of obtained coating reached optimal. However,when the addition of La_2O_3 was 1.0%,the hardness,resistance of thermal shock and resistance of high-temperature wear of the nickel-coated aluminum coating decreased,compared with the coating prepared with the La_2O_3 addition of 0.5%.
Adding rare-earth oxides could improve the structure and hardness of sprayed welding coatings. The sprayed nickel-coated aluminum coatings with adding different La_2O_3 contents were prepared on the surface of 20 steel by plasma spray welding. The microstructure and performance of coatings were studied by optical microscopy,SEM,EDS,X-ray diffractometer,micro-hardness tester,thermal shock test and high-temperature wear test. Results showed that the microstructures of nickel-coated aluminum plasma sprayed layer were dendrites,and the dendrites were some lath α-( Fe,Ni) martensite groups with intergranular reticular phase of γ-( Fe,Ni). These structures endowed the nickel-coated aluminum plasma sprayed coatings with good resistance of thermal shock at 750 ℃. The addition of 0.5% La_2O_3 improved the hardness of the nickel-coated aluminum plasma sprayed layer by 19.4%,but did not have obvious effect on the resistance of thermal shock. In addition,nickel-coated aluminum spray welding coating showed a good friction stability and ideal-high temperature wear resistance in high-temperature friction and wear tests at 500 ℃,which resulted from that the tissue structure possessed the γ-( Fe,Ni) intercrystalline tissues with good toughness and high-strength latitudinarian α-( Fe,Ni) slabs. When 0.5% La_2O_3 was added,the high-temperature wear-resistant performance of obtained coating reached optimal. However,when the addition of La_2O_3 was 1.0%,the hardness,resistance of thermal shock and resistance of high-temperature wear of the nickel-coated aluminum coating decreased,compared with the coating prepared with the La_2O_3 addition of 0.5%.
引文
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[3]李秉忠.表面工程应用实例[例10]等离子喷焊技术应用于新阀门制造和旧阀门再制造[J].中国表面工程,2009,22(3):75.
[4]邓世均.高科技时代的热喷涂技术IJ].材料保护,1995,28(8):12-15.
[5]王瑞权,邱葭菲,姚荣庆,等.等离子喷焊Cu Al Fe涂层组织及性能研究[J].热加工工艺,2014(18):118-120.
[6]张红霞,赵玉梅,师侦峰.稀土元素在金属表面改性中的应用[J].金属热处理,2011,36(3):91-94.
[7]王宝森,李建国.稀土硅铁合金粉末增强Fe-22CH喷焊层机理研究[J].材料科学与工艺,2002,10(4):408-411.
[8]李文生,王大锋,董洪峰.高铝青铜等离子喷焊层的组织及抗热震性能[J].粉末冶金材料科学与工程,2013(5):723-728.
[9]杨洪刚,李曙,刘阳,等.有限元模拟Ti N膜/碳钢基材体系的摩擦磨损试验[J].摩擦学学报,2009,29(4):293-298.