GCr15钢表面等离子熔覆硼化物覆层的高温氧化特征

High-temperature oxidation characteristics of plasma cladding boride coating on GCr15 steel surface

采用等离子熔覆的方法在GCr15钢表面制备了硼化物覆层。利用光学显微镜、扫描电镜（SEM）及能谱仪（EDS）、X射线衍射仪（XRD）等对熔覆层的组织结构、成分、物相进行分析,并研究覆层在600~850℃的高温氧化行为。结果表明：覆层组织由α-Fe、Mo2FeB2、（Mo,Cr,Fe）3B2和Fe（23）（C,B）6组成,与GCr15钢形成良好的冶金结合;熔覆层的高温氧化遵循抛物线规律,氧化激活能Ea=116.77 k J/mol;覆层在600~800℃为抗氧化级,主要以黏结相α-Fe氧化为主;800~850℃覆层为次抗氧化级,硼化物硬质相快速氧化,氧化层中气孔径增大并出现裂纹;熔覆层氧化受MoO3蒸发速度控制,氧化过程存在元素的扩散。

The boride coating was prepared on the surface of GCr15 steel by plasma cladding. Microstructure,composition and phase of the boride coating were analyzed by means of optical microscope（ OM）,scanning electron microscopy（ SEM）,energy dispersion spectrum（ EDS） analysis,X-ray diffractometer（ XRD）,and high temperature oxidation behaviors of the coating at 600-850 ℃ were investigated.The results show that the microstructure of the coating is composed of α-Fe,Mo2FeB2,（ Mo,Cr,Fe）3B2 and Fe（23）（ C,B）6 phases,and formed a good metallurgical bond with the GCr15 steel. The high temperature oxidation kinetics of the coating follows the parabolic law,and the values of oxidation activation energy（ Ea） is 116. 77 k J/mol. The coating at 600-800 ℃ is anti-oxidation level,mainly by α-Fe oxidation. The coating at 800-850 ℃ is secondary anti-oxidation level,the boride hard phase is rapidly oxidized,the gas pore size increases and cracks appear in oxidation layer. The oxidation of the coating is controlled by the evaporation rate of MoO3,and the diffusion of elements exists in the oxidation process.