The Multi layer coating of Ni60 alloy was got by multi layer laser cladding. The height of the coating was about 12mm and the wall of the coating was perpendicular to the base. The microstructure of the coating was ...The Multi layer coating of Ni60 alloy was got by multi layer laser cladding. The height of the coating was about 12mm and the wall of the coating was perpendicular to the base. The microstructure of the coating was made up of fine dendrite. The conjunction between layers was good.展开更多
The structure of the yttrium modified Co-base alloy layers formed by laser cladding on 2Cr13 and 1Cr18Ni9Ti steel surfaces and its hot corrosion performance have been investigated systematically.The re- sults show tha...The structure of the yttrium modified Co-base alloy layers formed by laser cladding on 2Cr13 and 1Cr18Ni9Ti steel surfaces and its hot corrosion performance have been investigated systematically.The re- sults show that the Y-containing cobalt base clad alloy has a finer microstructure and higher corrosion re- sistance to the salt mixture of 75% Na_2SO_4+25%NaCl at high temperature.The unique properties are ob- tained with addition of 0.875% Y for the formation of a continuous and compact oxide scale.The compact scale may act as a barrier for the inward diffusion of oxygen and sulphur and also for the outward diffusion of alloying elements.展开更多
By laser multi-layer cladding using a pulsed Nd-YAG irradiation the thickness of the cladding zone Mg-based alloys(ZM2 and ZM5) can reach about 1.0 mm.The microstructure of the substrate and the cladding zone was stud...By laser multi-layer cladding using a pulsed Nd-YAG irradiation the thickness of the cladding zone Mg-based alloys(ZM2 and ZM5) can reach about 1.0 mm.The microstructure of the substrate and the cladding zone was studied using optical microscope, scanning electron microscopy(SEM), X-ray diffractometry(XRD) and micro hardness analysis. It is observed that constituent of ZM5 alloy is δ+Mg 17Al 12, that of ZM2 alloy is α+MgZn+Mg 9Ce. That of cladding layer ZM2 alloy(L-ZM2) is Mg+Mg 2Zn 11+MgCe; while that of the cladding layer ZM5 alloy(L-ZM5) is Mg+Mg 32(Al, Zn) 49. The hardness of the cladding area can be increased to values above HV127. Very fine uniform microstructure and the produced new phases of nanometer/sub-micrometer order were obtained. Now, many repaired Mg-based alloy components have been passed by flying test in outside field.展开更多
TiC/Ti composite layers were produced by laser melting the preplaced mixture of Ti and TiC powders. The results show that the microstructure, microhardness and wear resistance of the clad layer are all evaluated. The ...TiC/Ti composite layers were produced by laser melting the preplaced mixture of Ti and TiC powders. The results show that the microstructure, microhardness and wear resistance of the clad layer are all evaluated. The composite layer consists of TiC and α-Ti phases. TiC in the clad zone exists in the form of fine dendrites and Ti fills among TiC dendrites, which has a typical structure of TiC/Ti composite. The microhardness of the composite coating is significantly enhanced as high as HV_ 0.2940 as compared to HV_ 0.2345 of the substrate region. The composite layer has excellent wear resistance compared to titanium alloy.展开更多
The Co-based alloy coatings had been prepared by laser cladding and vacuum fusion sintering. Microstructures of the coatings were investigated and the performance of thermal cycling was also tested using scanning elec...The Co-based alloy coatings had been prepared by laser cladding and vacuum fusion sintering. Microstructures of the coatings were investigated and the performance of thermal cycling was also tested using scanning electron microscopy （ SEM） and X-ray diffraction （ XRD ）. The results show that the coatings and substrates combine well. The main phase compositions of laser cladding coating are T-Co, Cr23 C6 and Ni2 9 Cro. 7 Feo. 36, while vacuum fusion sintering coating consists of Co, Cr7 C3, and Ni2.9 Cro. 7 Feo. 36. After thermal cycling, the minimum hot cracking width of laser cladding coating is 14 μm; moreover, laser cladding coating maintains high hardness and hot-cracking susceptibility. Those are beneficial to high temperature wear resistance of hot work dies.展开更多
Composite coatings made of nano-Y_2O_3/cobalt-based alloy and produced by crosscurrent CO_2 laser on Ni-based superalloy are introduced. Cross-section or surface of the coatings was examined to reveal their microstruc...Composite coatings made of nano-Y_2O_3/cobalt-based alloy and produced by crosscurrent CO_2 laser on Ni-based superalloy are introduced. Cross-section or surface of the coatings was examined to reveal their microstructure using optical microscope, SEM, including EDS microanalysis, TEM and XRD. The results show that some equilibrium or non-equilibrium phases, such as γ-Co, Cr_(23)C_6, Y_2O_3 and ε-Co exist in the coatings. Fine and short dendritic microstructure and columnar to equiaxed transition (CET) occurred by adding nano-Y_2O_3 particles. With the increasing amount of nano-Y_2O_3 (1%, mass fraction), fully equiaxed crystallization appeared. These are caused by nano-Y_2O_3 particles acting as new nucleation site and rapid solidification of the melt. The results also show that inhomogeneous dispersion of nano-Y_2O_3 results in the formation of ε-Co phase in the coatings. The sub-microstructure of the clad is stacking fault. The mechanism of the formation of equiaxed grains is also analyzed.展开更多
文摘The Multi layer coating of Ni60 alloy was got by multi layer laser cladding. The height of the coating was about 12mm and the wall of the coating was perpendicular to the base. The microstructure of the coating was made up of fine dendrite. The conjunction between layers was good.
基金Research Project supported by the Corrosion Science Laboratory,Academia Sinica
文摘The structure of the yttrium modified Co-base alloy layers formed by laser cladding on 2Cr13 and 1Cr18Ni9Ti steel surfaces and its hot corrosion performance have been investigated systematically.The re- sults show that the Y-containing cobalt base clad alloy has a finer microstructure and higher corrosion re- sistance to the salt mixture of 75% Na_2SO_4+25%NaCl at high temperature.The unique properties are ob- tained with addition of 0.875% Y for the formation of a continuous and compact oxide scale.The compact scale may act as a barrier for the inward diffusion of oxygen and sulphur and also for the outward diffusion of alloying elements.
文摘By laser multi-layer cladding using a pulsed Nd-YAG irradiation the thickness of the cladding zone Mg-based alloys(ZM2 and ZM5) can reach about 1.0 mm.The microstructure of the substrate and the cladding zone was studied using optical microscope, scanning electron microscopy(SEM), X-ray diffractometry(XRD) and micro hardness analysis. It is observed that constituent of ZM5 alloy is δ+Mg 17Al 12, that of ZM2 alloy is α+MgZn+Mg 9Ce. That of cladding layer ZM2 alloy(L-ZM2) is Mg+Mg 2Zn 11+MgCe; while that of the cladding layer ZM5 alloy(L-ZM5) is Mg+Mg 32(Al, Zn) 49. The hardness of the cladding area can be increased to values above HV127. Very fine uniform microstructure and the produced new phases of nanometer/sub-micrometer order were obtained. Now, many repaired Mg-based alloy components have been passed by flying test in outside field.
文摘TiC/Ti composite layers were produced by laser melting the preplaced mixture of Ti and TiC powders. The results show that the microstructure, microhardness and wear resistance of the clad layer are all evaluated. The composite layer consists of TiC and α-Ti phases. TiC in the clad zone exists in the form of fine dendrites and Ti fills among TiC dendrites, which has a typical structure of TiC/Ti composite. The microhardness of the composite coating is significantly enhanced as high as HV_ 0.2940 as compared to HV_ 0.2345 of the substrate region. The composite layer has excellent wear resistance compared to titanium alloy.
文摘The Co-based alloy coatings had been prepared by laser cladding and vacuum fusion sintering. Microstructures of the coatings were investigated and the performance of thermal cycling was also tested using scanning electron microscopy （ SEM） and X-ray diffraction （ XRD ）. The results show that the coatings and substrates combine well. The main phase compositions of laser cladding coating are T-Co, Cr23 C6 and Ni2 9 Cro. 7 Feo. 36, while vacuum fusion sintering coating consists of Co, Cr7 C3, and Ni2.9 Cro. 7 Feo. 36. After thermal cycling, the minimum hot cracking width of laser cladding coating is 14 μm; moreover, laser cladding coating maintains high hardness and hot-cracking susceptibility. Those are beneficial to high temperature wear resistance of hot work dies.
文摘Composite coatings made of nano-Y_2O_3/cobalt-based alloy and produced by crosscurrent CO_2 laser on Ni-based superalloy are introduced. Cross-section or surface of the coatings was examined to reveal their microstructure using optical microscope, SEM, including EDS microanalysis, TEM and XRD. The results show that some equilibrium or non-equilibrium phases, such as γ-Co, Cr_(23)C_6, Y_2O_3 and ε-Co exist in the coatings. Fine and short dendritic microstructure and columnar to equiaxed transition (CET) occurred by adding nano-Y_2O_3 particles. With the increasing amount of nano-Y_2O_3 (1%, mass fraction), fully equiaxed crystallization appeared. These are caused by nano-Y_2O_3 particles acting as new nucleation site and rapid solidification of the melt. The results also show that inhomogeneous dispersion of nano-Y_2O_3 results in the formation of ε-Co phase in the coatings. The sub-microstructure of the clad is stacking fault. The mechanism of the formation of equiaxed grains is also analyzed.
