【作者】 杨勇；

【导师】 孙玉福；

【作者基本信息】 郑州大学 ， 材料加工工程， 2014， 硕士

【摘要】 耐磨件工作时，受到摩擦作用使零件尺寸改变而失效。为了提高其使用性能、延长其服役寿命，本文采用氩气保护电阻炉熔覆技术，以不同熔覆工艺参数（熔覆温度分别为1200℃、1230℃、1260℃，保温时间分别为10min、30min、50min），在A3钢板表面制备一层厚度为1~2mm的WC增强镍基熔覆层，采用OM、SEM、XRD、显微硬度仪、洛氏硬度仪及磨损试验机等检测设备，分析碳化钨的分布、熔覆层组织特征及相的组成、钢板基体组织及结合方式，测试熔覆层显微硬度、洛氏硬度，进行磨损试验及磨损形貌的观察，优化熔覆层合金粉末中碳化钨含量及熔覆工艺。研究结果表明：熔覆试样由钢板基体、过渡层和熔覆层三部分组成，在1230℃最高熔覆温度下保温时间10min时，试样熔覆层表面平整、过渡层宽度为150um~250um，碳化钨分解量少。过渡层中各元素含量介于钢板和熔覆层粉末中元素的含量，各元素扩散充分，钢板和熔覆层以冶金结合为主。熔覆层组织主要包括粘结相、碳化钨及镍基自熔性合金粉末形成的硬质相。XRD分析结果显示，熔覆层粘结相主要是奥氏体，其包括Fe0.64Ni0.36和Ni2.9Cr0.7Fe0.36等相；碳化钨主要包括WC和W2C；硬质相主要由碳化物及硼碳复合化合物等相组成，其中碳化物则分别以M23C6和M7C3两种形式存在。距离过渡层较近的钢板基体组织以珠光体为主。随着碳化钨含量的增加，熔覆层的洛氏硬度不断提高；当碳化钨含量为35%时，熔覆层洛氏硬度值为47.3HRC，是钢板基体硬度值的3倍以上，比65Mn提高约25%。熔覆层中粘结相显微硬度为654.9HV、碳化钨为1695.3HV。随着碳化钨含量的增加，磨损率总体上呈现先减小后增加的趋势，当碳化钨含量在35%时耐磨性最好，磨损率为0.08mg/m，约是钢板基体耐磨性5倍，约是65Mn耐磨性4倍。试样端面磨损形貌中犁沟数量少、深度浅，碳化钨等硬质颗粒剥落量少。综上所述，当熔覆层合金粉末中碳化钨含量为35%，熔覆温度为1230℃、保温时间为10min时，熔覆层表面平整，与钢板基体达到冶金结合，熔覆层组织主要包括粘结相、碳化钨及镍基自熔性合金粉末形成的硬质相，其中碳化钨均匀分布在熔覆层中；洛氏硬度为47.3HRC，比65Mn提高约25%；磨损率为0.08mg/m，约是65Mn耐磨性4倍，具有良好的综合性能。该技术可广泛应用于对耐磨件表面改性及修复。更多还原

【Abstract】 When wear parts works, due to the friction of material, easy to failure because ofthe size of its changes. In order to improve the mechanieal performance of vibrationscreen plate and prolong its operational life. The Argon gas protection resistancefurnace was used in this article with different cladding process (the claddingtemperature1200℃,1230℃,1260℃respectively and the holding time10min,30min,50min respectively), a nickel-based cladding layer reinforced by WC which isabout1~2mm thickness was fabricated on A3steel plate surface; Meanwhile, theoptical microscope (OM), scanning electron microscope (SEM), X-ray diffractometer(XRD), micro-hardness tester, rock hardness tester and wear tester and otherequipment was usied to analyzed the distribution of WC, the microstructure, phasecomposition and combination mode of cladding layer and steel matrix organizationchanged; the cladding layer micro-hardness and rock hardness of cladding layer wastested, while the wear resistance test was carried out and then the wear morphologyobservation was performed by SEM to evaluate the wear resistance property ofcladding layer. Optimization of WC content in the alloy powder of cladding layer andthe cladding process.The results of the present study showed that the specimen was consist of steelmatrix, transition layer and cladding layer after cladding,when the specimens wasroasted by1230℃maximum cladding temperature for10min, the surface ofcladding layer smooth more, transition layer width is150~250um and less WCdecomposition. The content of each element in the transition layer between thecontent of elements in the steel matrix and cladding layer of powder, this suggeststhat each element diffusion in cladding process fully, the steel matrix and claddinglayer is given priority to with metallurgical bonding.The microstructure of cladding layer mainly consisted of binding phase, wolframcarbide and hard phase formed by nickel-based fluxed alloy powder. XRD analysisshows that the binding phase is mainly composed of austenite, which includes Fe0.64 Ni0.36, Ni2.9Cr0.7Fe0.36phase and other phase; wolfram carbide tends to dissolve outto form WC and W2C; hard phase is mainly composed of boron carbide, carboncomposite compounds and other phase composition, nd the carbide tends to dissolveout to form M23C6and M7C3respectively. The microstructure of steel matrix thatclosed transition layer is given priority to with pearlite.With increasing of WC content, rock hardness of cladding layer ascend; thesamples containing35.%WC presented the best rock hardness of47.3HRC, morethan three times that of steel matrix rock hardness, about25%higher than65Mn. Themicro-hardness of binding phase and wolfram carbide in cladding layer was654.9HV,and1695.3HV respectively.With increasing of WC content, the wear rate showed a fluctuation and thesamples containing35%WC presented the best wear resistance with0.08mg/m,which is about5times than the wear resistance of steel matrix and is four timeshigher than65Mn. There is a minute quantity and shallow depth of furrows in thewear morphology of the specimen, meanwhile, the quantity of wolfram carbide andother hard particle flaking is little.In conclusion, the surface of cladding layer smooth more, the steel matrix andcladding layer is given priority to with metallurgical bonding, the microstructure ofcladding layer mainly consisted of binding phase, wolfram carbide and hard phaseformed by nickel-based fluxed alloy powder,where the distribution of wolframcarbide is well-proportioned in cladding layer with35%WC content in cladding layeralloy powder after roasted by1230℃cladding temperature for10min,thespecimens represents excellent combination of microstructure. Under this condition,;its rock hardness reached47.3HRC which is about25%higher than65Mn, and wearrate reached0.08mg/m which is four times higher than65Mn. This technology canbe widely used in wear parts surface modification and repaired.更多还原