摘要
采用热反应扩散沉积法(TRD)对有无预渗氮处理的SKD11钢试样分别以950、900、850、800和750℃进行气体热渗铬。利用SEM和EDS测量铬原子扩散深度;根据经典动力学理论计算活化能及扩散系数;利用XRD分析相结构;再进行维氏硬度测量和耐磨实验。结果表明,经渗氮前处理的渗铬试样在各温度下铬原子扩散深度比未经渗氮均有增加,有预渗氮渗铬层最深达到20μm,未经渗氮渗铬层只有13μm,其活化能分别为106.09和147.47 k J/mol,表面硬度分别为1610及1760 HV。在各实验温度下,经渗氮预处理渗铬试样的耐磨性均比未经渗氮试样好,渗铬温度高于850℃耐磨性优于基材,低于850℃硬度虽然高于基材,但耐磨性不及基材。在较高温度(950和900℃)渗铬时,有渗氮预处理试样的渗铬层结构为Cr2C和Cr2N相,无渗氮预处理为Cr2C相;在较低温度(800和750℃)渗铬时,有渗氮预处理试样的渗铬层结构为Cr7C3和Cr N相,无渗氮预处理为Cr7C3相。
Gas chromizing processes on SKD11 steel with and without nitriding pre-treated by thermal reactive diffusion / deposition( TRD) at different temperatures of 950,900,850,800 and 750 ℃ were studied. The chromium's diffusion depth was measured by scanning electronic microscopy( SEM) and energy dispersive spectrometer( EDS). The activation energy and diffusion coefficient were calculated on the basis of classical kinetic theory. The crystal structure was also identified by X-ray diffraction( XRD). The Vickers hardness was measured and the wear resistance was tested as well. The results show that the diffusion depth of chromizing layer on the steel with nitriding pre-treatment at different temperatures is more than those of without nitriding. The maximum depth of the chromizing layer with nitriding pre-treatment is 20 μm,while without nitriding pre-treatment is 13 μm. Their activation energies are 106. 09 k J / mol and 147. 47 k J / mol,respectively,while their surface hardnesses are 1610 HV and 1760 HV,respectively. The wear resistance of the steel sample with nitriding pre-treatment is greater than that of the steel sample without nitriding pre-treatment at each test temperature. At chromizing temperatures higher than 850 ℃,the wear resistance of steel sample is greater than that of substrate. At chromizing temperatures lower than 850 ℃,the hardness of steel sample is greater than that of substrate,but the wear resistance of steel sample is less than that of substrate. At higher chromizing temperatures( 950 and 900 ℃),the chromizing layer's crystal structure of the steel sample with nitriding pre-treatment are Cr2 C and Cr2 N,while without nitriding pre-treatment is Cr2 C. At lower chromizing temperatures( 800 and 750 ℃),the chromizing layer's crystal structure of the steel sample with nitriding pre-treatment are Cr7C3 and Cr N,while without nitriding pre-treatment is Cr7C3.
出处
《材料热处理学报》
EI
CAS
CSCD
北大核心
2015年第2期209-213,共5页
Transactions of Materials and Heat Treatment
基金
福建省中青年教师教育科研项目(JA13380)
关键词
热热反应扩散/沉积
扩散系数
活化能
耐磨性
thermo-reactive diffusion / deposition
diffusion coefficient
activation energy
wear resistance
