前驱体碳化复合等离子熔覆涂层

Plasma cladding coatings by precursor carbonization-composition process

  • 摘要: 以钛铁粉、铬粉、铁粉和碳的前驱体(蔗糖)等为原料,通过前驱体碳化复合技术制备了碳化复合粉,并利用等离子熔覆技术在Q235钢表面制备了Fe-Cr-C和Fe-Cr-C-Ti涂层.采用X射线衍射和扫描电镜对涂层的相组成和显微组织结构进行了分析.结果表明:Fe-Cr-C涂层由(Cr,Fe)7C3初生碳化物和菊花瓣状分布共晶碳化物(Cr,Fe)7C3与奥氏体组织组成;Fe-Cr-C-Ti涂层由原位合成的TiC相和(Cr,Fe)7C3共晶相与奥氏体相构成.这两种涂层与基体之间都是冶金结合.涂层中碳化物TiC的体积分数呈现梯度分布,并且涂层的熔合区和中部区域TiC颗粒形状多为等轴状颗粒,涂层的表层区域部分TiC颗粒多为树枝晶颗粒.与Fe-Cr-C涂层相比较,Fe-Cr-C-Ti涂层的抗开裂性更好.Fe-Cr-C和Fe-Cr-C-Ti两涂层的平均显微硬度约是750 HV0.2,是基体金属的3.2倍,从涂层表面到熔合区相差不大.

     

    Abstract: A process of preparing Fe-Cr-C composite powder for precursor carbonization-composition process was developed using the compacts of mixed ferrotitanium, chromium, iron and carbon precursor (saccharose) powers as raw materials, and Fe-Cr-C and Fe-Cr-C-Ti composite coatings were synthesized and deposited on Q235 steel substrates by plasma cladding technology. The phase composition and microstructure of the composite coatings were analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It is shown that the Fe-Cr-C composite coating consists of (Cr,Fe)7C3 primary phase, (Cr,Fe)7C3 eutectics with a petal-like distribution and austenite, but the Fe-Cr-C-Ti composite coating is composed of in situ TiC and (Cr,Fe)7C3 eutectics and austenite. The two types of composite coatings are also metallurgically bonded to the substrates. The volume content of TiC in the coating shows a gradient distribution. Generally, TiC phases in the fusion zone and central regions are equiaxed, and TiC phase in the surface is dendritic. Compared with the Fe-Cr-C composite coating, the Fe-Cr-C-Ti composite coating has better anti-cracking. The average microhardnesses of the Fe-Cr-C and Fe-Cr-C-Ti composite coatings are about 750 HV0.2, 3.2 times as large as the microhardness of the based metal, and this value changes little from the surface to the fusion zone.

     

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