To improve the wear resistance of Cr5 steel, wear-resistant layers with lamellar eutectic microstructure were fabricated by laser surface alloying（LSA）, which is dependent on the in situ reaction between Cr and B_4C...To improve the wear resistance of Cr5 steel, wear-resistant layers with lamellar eutectic microstructure were fabricated by laser surface alloying（LSA）, which is dependent on the in situ reaction between Cr and B_4C. Our results indicated that the hypoeutectic structures of the LSA layers were divided into interdendritic eutectic structures and dendrites. The area fraction of the eutectic structures increased with increasing laser scanning speed, which improved the hardness and wear resistance of the LSA layers. The average hardness of the LSA layer prepared at a scanning speed of 8 mm/s was HV_（0.2） 883.9, which was 1.8 times greater than that of the traditional quenched layer（approximately HV 480）. After sliding for 659.4 m, the specimen prepared at a scanning speed of 8 mm/s exhibited a volume loss of 0.0323 mm^3, which was only 29.5% of the volume loss of the traditional quenched specimen.展开更多
Laser surface cladding with Al-Si powders was applied to a Mg-6Zn-1Ca magnesium alloy to improve its surface properties.The microstructure,phase components and chemical compositions of the laser-clad layer were analyz...Laser surface cladding with Al-Si powders was applied to a Mg-6Zn-1Ca magnesium alloy to improve its surface properties.The microstructure,phase components and chemical compositions of the laser-clad layer were analyzed by using X-ray diffractometry(XRD),scanning electron microscopy(SEM)and energy dispersive spectrometry(EDS).The results show that the clad layer mainly consists ofα-Mg,Mg2Si dendrites,Mg17Al12and Al3Mg2phases.Owing to the formation of Mg2Si,Mg17Al12and Al3Mg2intermetallic compounds in the melted region and grain refinement,the microhardness of the clad layer(HV0.025310)is about5times higher than that of the substrate(HV0.02554).Besides,corrosion tests in the NaCl(3.5%,mass fraction)water solution show that the corrosion potential is increased from-1574.6mV for the untreated sample to-128.7mV for the laser-clad sample,while the corrosion current density is reduced from170.1to6.7μA/cm2.These results reveal that improved corrosion resistance and increased hardness of the Mg-6Zn-1Ca alloy can be both achieved after laser cladding with Al-Si powders.展开更多
为提高球墨铸铁的表面性能,采用高速激光熔覆技术在其表面制备了Ni基合金涂层。分析了该涂层的物相、表面硬度、耐磨性和耐腐蚀性。结果表明:Ni基合金涂层主要由γ-Ni、Cr23C6、Ni2Si及Ni3B相组成。涂层表面平均硬度约为球墨铸铁的1.58...为提高球墨铸铁的表面性能,采用高速激光熔覆技术在其表面制备了Ni基合金涂层。分析了该涂层的物相、表面硬度、耐磨性和耐腐蚀性。结果表明:Ni基合金涂层主要由γ-Ni、Cr23C6、Ni2Si及Ni3B相组成。涂层表面平均硬度约为球墨铸铁的1.58倍,磨损量相较于基体磨损量减少65.7%;涂层以磨粒磨损为主并带有少量的剥落坑,基体主要为黏着磨损。Ni基涂层的自腐蚀电位Ecorr比基体的提高187.1 m V,同频时阻抗值大于基体的,其耐蚀性优于球墨铸铁的耐蚀性。展开更多
基金financially supported by the Joint Funds of the National Natural Science Foundation of China and Liaoning Province,China (No.U15082213)the Frontier and Key Technological Innovation Special Funds of Guangdong Province,China (No.2015B010122001)the Fundamental Research Funds for the Central Universities (No.N130810001)
文摘To improve the wear resistance of Cr5 steel, wear-resistant layers with lamellar eutectic microstructure were fabricated by laser surface alloying（LSA）, which is dependent on the in situ reaction between Cr and B_4C. Our results indicated that the hypoeutectic structures of the LSA layers were divided into interdendritic eutectic structures and dendrites. The area fraction of the eutectic structures increased with increasing laser scanning speed, which improved the hardness and wear resistance of the LSA layers. The average hardness of the LSA layer prepared at a scanning speed of 8 mm/s was HV_（0.2） 883.9, which was 1.8 times greater than that of the traditional quenched layer（approximately HV 480）. After sliding for 659.4 m, the specimen prepared at a scanning speed of 8 mm/s exhibited a volume loss of 0.0323 mm^3, which was only 29.5% of the volume loss of the traditional quenched specimen.
基金Project(2016YBF0701205) supported by the National Key Research and Development Program of ChinaProjects(51271121,51471109) supported by the National Natural Science Foundation of ChinaProject(13KY0501) supported by Shanghai University of Engineering Science Innovation Fund for Graduate Students,China
文摘Laser surface cladding with Al-Si powders was applied to a Mg-6Zn-1Ca magnesium alloy to improve its surface properties.The microstructure,phase components and chemical compositions of the laser-clad layer were analyzed by using X-ray diffractometry(XRD),scanning electron microscopy(SEM)and energy dispersive spectrometry(EDS).The results show that the clad layer mainly consists ofα-Mg,Mg2Si dendrites,Mg17Al12and Al3Mg2phases.Owing to the formation of Mg2Si,Mg17Al12and Al3Mg2intermetallic compounds in the melted region and grain refinement,the microhardness of the clad layer(HV0.025310)is about5times higher than that of the substrate(HV0.02554).Besides,corrosion tests in the NaCl(3.5%,mass fraction)water solution show that the corrosion potential is increased from-1574.6mV for the untreated sample to-128.7mV for the laser-clad sample,while the corrosion current density is reduced from170.1to6.7μA/cm2.These results reveal that improved corrosion resistance and increased hardness of the Mg-6Zn-1Ca alloy can be both achieved after laser cladding with Al-Si powders.
文摘为提高球墨铸铁的表面性能,采用高速激光熔覆技术在其表面制备了Ni基合金涂层。分析了该涂层的物相、表面硬度、耐磨性和耐腐蚀性。结果表明:Ni基合金涂层主要由γ-Ni、Cr23C6、Ni2Si及Ni3B相组成。涂层表面平均硬度约为球墨铸铁的1.58倍,磨损量相较于基体磨损量减少65.7%;涂层以磨粒磨损为主并带有少量的剥落坑,基体主要为黏着磨损。Ni基涂层的自腐蚀电位Ecorr比基体的提高187.1 m V,同频时阻抗值大于基体的,其耐蚀性优于球墨铸铁的耐蚀性。
