Microstructural development and wear properties analyses of Fe-based coatings on bainitic steel by laser cladding

Wear-resistant Fe-based coating was prepared by high-speed laser cladding on bainitic steel.The influence of laser scanning speed on microstructure,microhardness,and wear resistance of cladding coating was investigated.Scanning electron microscopy results showed that the coating was mainly composed of dendrite and interdendrite.Scanning electron microscope images were converted by binary algorithm to facilitate statistics of dendrite and interdendrite area.Statistical results indicate that by accelerating the scanning speed,the interdendrite eutectic structure increased.According to energydispersive X-ray spectroscopy and X-ray diffraction results,the interdendrite was enriched with elements Cr,Mo,and B,and main structures in the coating wereα-Fe,γ-Fe,and M(23)C_(6).The hardness of the coating was much higher than that of the substrate.Elements diffused from coating to substrate,resulting in a transition zone of hardness.Moreover,with an increase in the scanning speed,the diffusion of elements at the coating–matrix interface decreased,while the hardness and wear resistance of the coating increased.Grain refinement and interdendrite(γ-Fe,M_(23)C_(6))increasing due to high scanning speed were the major contributors to the increase in hardness and wear resistance.

纳米孪晶强化贝氏体化涂层及其耐磨性

目的通过诱发纳米孪晶强化贝氏体化涂层强度及耐磨性。方法在250℃对中碳合金钢进行激光熔覆,并进行等温处理。通过残余应力测试、X射线衍射试验、扫描电子显微镜和透射电子显微镜观察、显微硬度和纳米压痕测试、往复磨损试验及磨损形貌表征,分别评价激光熔覆涂层的残余应力、物相、显微组织与结构、硬度梯度及微观硬度\耐磨性能。结果激光熔覆涂层平行和垂直激光移动方向的平均应力值分别为(209±20)MPa和(319±21)MPa。激光熔覆引入大量位错结构,使残余奥氏体尺寸降低至(37.5±2.5)nm。两组试样均为无碳化物贝氏体组织,其显微组织由针状的贝氏体铁素体以及残余奥氏体组成。在激光热作用及后续等温过程中,显微组织明显细化,并伴随生成大量塑性良好的纳米孪晶结构。激光熔覆涂层的平均显微硬度为650HV,较基体的平均硬度提升了约25%。相同磨损时间下,熔覆层的磨损体积为0.675 mm3,基体的磨损体积为1.142 mm3,纳米孪晶结构的形成大大提升了中碳合金钢的抗粘着磨损性能。结论在特定温度对中碳合金钢进行激光熔覆可以制备贝氏体化涂层,在热应力作用下,显微组织中形成的纳米孪晶结构能够对涂层增强增韧,同时提高其抗粘着磨损性能。

激光熔覆纳米贝氏体涂层的组织与性能

采用高功率CO2激光熔覆铁基合金粉末,获得了无裂纹、稀释率低、成形良好的熔覆涂层。利用光学显微镜(OM)、扫描电镜(SEM)、透射电镜(TEM)、X射线衍射(XRD)对熔覆层的显微组织进行了观察与分析,通过硬度测试与拉伸试验考察了涂层的力学性能。结果显示:熔覆层为纳米贝氏体与残余奥氏体的复合组织,均匀分布的贝氏体铁素体板条厚度为50～80 nm,贝氏体板条间为厚度10～30 nm更为细小的残余奥氏体薄膜;熔覆层平均硬度为610 HV,熔覆涂层的抗拉强度为1 280 MPa,延伸率为6.41%,拉伸断口形貌为韧窝断口。

高速钢热处理宝典六则

作者从事高速钢热处理50年,就分级淬火、回火程度及次数、二次贝氏体处理、摩擦焊刀具热处理、深冷处理、涂层共六个经典问题,谈点体会和大家分享。

稀土Ce对激光熔覆高硼贝氏体涂层性能的影响

利用激光熔覆制备了不同Ce含量的高硼贝氏体涂层。采用扫描电镜对不同Ce含量的涂层组织进行表征;利用显微硬度计检测熔覆层显微硬度;通过万能拉伸机测试熔覆涂层的断裂韧性;用往复摩擦磨损试验机测试涂层的磨损性能。结果表明:经稀土Ce改性后,初生奥氏体晶粒尺寸减小,晶间网格状硼化物形态得到改善,呈现断网或颗粒状。三点弯曲断裂韧性得到改善,断口由沿晶脆断转变为准解理断裂。随着Ce含量的增加,熔覆涂层平均摩擦因数先减小后增大,磨痕中都存在严重的疲劳剥落。