激光熔覆304不锈钢涂层的组织及耐蚀性

Microstructure and corrosion resistance of 304 stainless steel coating by laser cladding

为提高普通碳钢表面耐蚀性,利用5 kW横流CO2激光加工设备在45钢表面激光熔覆制备304不锈钢涂层。采用光学显微镜、XRD和SEM等手段对所制备涂层的显微组织及相组成进行分析,并分别利用化学侵蚀实验和阳极极化曲线对涂层的耐腐蚀性能进行测试。结果表明:熔覆层由铁素体和奥氏体双相组成,自界面处到顶端逐渐由单一粗大的柱状晶向尺寸约为5~8μm的致密细小的等轴晶过渡;在15%FeCl3溶液中静置24 h后,基材被腐蚀而熔覆层无明显变化;熔覆层的自腐蚀电位比基材高290 mV,仅比商用304不锈钢低70 mV,而3者之中熔覆层的自腐蚀电流密度最低。

In order to improve the surface corrosion resistance of 45 steel,AISI 304 stainless steel powder was used to fabricate laser cladding coatings on surface of the 45 steels substrate.The microstructure of the laser cladding sample was observed by metallographic microscopy and scanning electron microscope,the phase composition was determined by X-ray diffraction,the corrosion resistance was detected by chemical immersion test and electrochemical corrosion test.The results show that the cladding layer is composed of ferrite and austenite phases containing transition from big columnar crystals to small equiaxed grains whose's size is 5- 8 μm.Chemical immersion test shows the corrosion resistance of substrate is greatly improved by laser cladding AISI 304 stainless steel coatings.Polarization curves indicate that the self-corrosion potential of the cladding layer is over 320 mV higher than that of the substrate and just 70 mV lower than that of the 304 stainless steel,while corrosion current density of the cladding layer is the lowest.