胡肇炜,李文戈.激光熔覆原位合成Mo2NiB2涂层工艺研究[J].表面技术,2017,46(8):1-6
激光熔覆原位合成Mo2NiB2涂层工艺研究
Process Research of In-situ Synthesis of Mo2NiB2 Coating by Laser Clad-ding
投稿时间:2017-01-18  修订日期:2017-08-20
DOI:10.16490/j.cnki.issn.1001-3660.2017.08.001
中文关键词:  激光熔覆  原位合成  Mo2NiB2  工艺参数  凝固
英文关键词:laser cladding  in-situ synthesis  Mo2NiB2  process parameters  solidification
基金项目:国家自然科学基金(51572168,51172140)
作者单位
胡肇炜 上海海事大学,上海 201306 
李文戈 上海海事大学,上海 201306 
AuthorInstitution
HU Zhao-wei Shanghai Maritime University, Shanghai 201306, China 
LI Wen-ge Shanghai Maritime University, Shanghai 201306, China 
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中文摘要:
      目的 选择和优化激光熔覆工艺参数,以制备三元硼化物金属基陶瓷Mo2NiB2涂层。方法 通过激光熔覆原位合成法在碳钢表面制备了以Mo2NiB2为增强相的涂层,并采用金相显微镜、扫描电镜(SEM)及X射线衍射(XRD)对涂层组织进行分析。利用ANSYS计算熔覆过程的温度场,进而计算涂层凝固特征参数,即凝固形状控制因子。结果 微观组织分析表明,在激光功率为2500 W、扫描速度为1.5 mm/s、预置厚度为1 mm时,可获得细密、均匀的组织,涂层中白色部分为生成的Mo2NiB2,灰色部分为Fe、Ni固溶体。涂层与基体结合部位以平面晶形式生长,然后以树枝晶的方式远离界面生长。温度场及凝固特征参数的计算表明,温度梯度达105 ℃/m数量级,形状控制因子达109 (℃•s)/m2数量级。结论 激光功率的增加会使涂层中的枝晶组织趋于细密,形状因子K值大幅增大。凝固形状控制因子K为3×109~5×109 (℃•s)/m2时,凝固组织为平面晶,表现为“白亮带”;K为7×109 (℃•s)/m2以上时,凝固组织为树枝晶;K为13×109 (℃•s)/m2时,树枝晶晶粒出现明显的细化现象。
英文摘要:
      Mo2NiB2 ternary boride metal-base ceramic is of excellent wear resistance and corrosion resistance, and can be widely used in marine corrosion prevention covering ships, marine pipelines, ocean platform and harbor facilities. In-situ reaction produces chemical reaction under certain conditions by using different elements, and forms one or more reinforced phase(s) in metal substrate. Laser cladding in-situ synthesis method was a new method of preparing ternary boride coating on the surface of carbon steel. High laser energy was used as excitation condition of in-situ reaction to produce superfine reinforced ceramic phase directly on the surface of carbon steel. As laser cladding is a quick heating and cooling technology, its process become more complex once being combined with in-situ synthesis reaction technology. Therefore, technological parameter had significant effects on coating. Calculation of solidification characteristic parameter contributed to selection and optimization of technological parameters. A coating containing Mo2NiB2 reinforced phase was prepared on the surface of carbon steel by laser cladding in-situ synthesis method. Microstructure of the coating was analyzed with metallographic microscopy, scanning electron microscope and X ray diffractometer. Temperature field of cladding process was simulated with ANSYS and then solidification characteristic parameters, i.e., shape control factors, were calculated. Microstructure analysis showed that refined and uniform microstructure was obtained when laser power was 2500 W, scanning speed was 1.5 mm/s and thickness of precoated layer was 1 mm. White part in the coating was Mo2NiB2 and gray parts were Fe, Ni solid solutions. Site where the coating was bond to the substrate grew in the form of planar crystal, and then grew away from the interface in the mode of dendrite. Calculation of temperature field and solidification characteristic parameter showed that temperature gradient reached 105 ℃/m, shape control factor was at least 109 (℃•s)/m2. Dendritic structure tends to be refined and and shape control factor (K) increases sharply as laser power increased. When K is 3×109~5×109 (℃•s)/m2, the solidification structure is planar crystal, and appears as “white bright band”; when K is over 7×109 (℃•s)/m2, the solidification structure was dendrite crystal; when K is 13×109 (℃•s)/m2, the crystalline grain is refined.
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