等离子喷焊原位生成TiC硬质增强镍基耐磨层组织与性能

MICROSTRUCTURES AND PROPERTIES OF Ni-BASED WEAR RESISTANT LAYERS REINFORCED BY TiC GENERATED FROM IN SITU PLASMA SPRAY WELDING

通过等离子喷焊NiCrBSi+Ti混合粉末制备TiC硬质增强镍基复合耐磨层,利用OM,SEM,XRD及EDS研究了喷焊层微观组织、物相及元素组成特征,并利用显微硬度仪及磨料磨损试验机对喷焊层显微硬度及耐磨料磨损性能进行测试.结果表明,NiCrBSi+Ti混合粉末喷焊层主要包括由保留有共晶组织形态的(γ-Ni+β_1-Ni_3Si)与过共析组织(α-Fe+FeNi_3)组成的基体相,以及镶嵌于基体中的M_7C_3和M_(23)C_6等硬质相;CrB弥散分布于喷焊层中;原位生成的TiC一部分作为M_7C_3和M_(23)C_6等后析出相的形核核心,一部分以细小颗粒(<1μm)弥散于基体中,部分甚至偏聚为大尺寸TiC(>1μm)块体.Ti的加入,显著细化了喷焊层组织,Ti添加量为6%时,喷焊层性能最好,显微硬度可达800 HV_(0.5),磨损质量约为14.5 mg,耐磨性为纯NiCrBSi喷焊层的2倍以上.

Generally, wear is one of the main failure mechanisms for mold steel. The heavy financial loss will often occur if molds are out of service due to their hard manufacturing process and high cost of metal materials. Therefore, mold repairing is urgent and critical if they fail to function. Ni-matrix wear resistant composited layers reinforced by TiC generated from in situ plasma spray welding NiCrBSi＋Ti powders were prepared. The analysis instruments of OM, SEM, XRD and EDS were used to study the microstructural characterization, phase identification and chemical compositions of the layers. And the microhardness and wear resistance were tested using Vickers hardness tester and abrasion tester, respectively. The investigations demonstrated that the layers were mainly composed of basic phases （γ-Ni＋β1-Ni3Si） with eutectic features and hypereutectoid （α-Fe＋FeNi3） structures, in which hard phases M7C3 and M23C6 were embedded in the matrix. The phase CrB was distributed uniformly in the layers. One part of TiC generated from in situ reaction acted as the nucleation of the chromium compounds precipitates M7C3 and M23C6. The other part of TiC was also distributed in the base with the fine particles （〈1 μm） and even bigger size （〉1 μm）. Ti percentage rising, the microstructures of plasma spray welding layers were refined and the phase M23C6, increased while M7C3 decreased. When the Ti addition reached 6%, the layers had better performance with microhardness of 800 HV0.5. The wear mass loss of layers was 14.5 mg, which were more than 2 times of NiCrBSi layer.