钢表面激光熔覆原位合成TiN复合涂层
In-situ synthesis of TiN coating prepared by laser cladding
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摘要: 选用Ti机械球磨粉末在Q235钢基体表面进行激光熔覆,并实时通入氮气,使钛与氮气发生反应原位合成TiN涂层.运用SEM,XRD,EDS和BSE分析方法对激光熔覆层的组织及成分进行分析,并对熔覆层硬度、高温稳定性及耐腐蚀性进行测试.结果表明,涂层由TiN,TiO2和铁组成,涂层与基体形成了冶金结合,熔覆区组织成球形颗粒状,而稀释区组织多为树枝晶和针状晶,机械球磨过程可起到细化涂层晶粒作用.同时激光熔覆涂层具有较高的硬度及高温稳定性,当激光功率为1 000 W,扫描速度为600 mm/min时,TiN复合涂层最高表面显微硬度为951.5MPa,涂层耐腐蚀性不佳主要是因为涂层中孔洞及疏松等缺陷导致.Abstract: The TiN coating were developed on Q235 steel surface by laser cladding using mechanical milling Ti powder.The microstructure of the TiN coating were analyzed by using SEM, XRD EDS and BSE methods. Meanwhile, the hardness, high temperature stability and corrosion resistance of the cladded layers were also measured. The results showed that the TiN coating was composed of TiN, TiO2 and Fe and a metallurgical bonding was formed. Global particles can be seen in the fusion zone.However, two phases in the form of dendrites and needle platelets were found in the dilution zone. Ti powders can be refined and activated by mechanical milling process. Therefore, finer grain could be easily formed in the coatings by using milled powders. Furthermore, the microhardness and the high temperature stability were excellent. The highest microhardness of the coating was 951.5 MPa under the conditions of laser power 1 000 W and scanning speed 600 mm/min. The corrosion resistance of coating was not good because of the defect like porosity presented in the coating.