Appropriate laser cladding processing parameters for a Ni-Fe-Cr based alloy coating with good quality were studied using 3.5 kW diode laser.The characterization of the coating was investigated,and the influence of eac...Appropriate laser cladding processing parameters for a Ni-Fe-Cr based alloy coating with good quality were studied using 3.5 kW diode laser.The characterization of the coating was investigated,and the influence of each parameter was analyzed.The mechanical properties and wear resistance of the coating were compared with the corresponding chemical composition wrought and cast materials.The results showed that a coating with aspect ratio about 3,dilution ratio 8%-10%and wetting angle 35o-50°could be formed with the laser power 1200-1500 W,travelling speed 8-10 mm/s,powder feed rate 16-18 g/min and shield gas flow 15 l/min.The tensile strength of the coating reached 953 MPa which was higher than that of wrought material 918 MPa and cast material 830 MPa.The microhardness of multi-layer coating was higher than that of single layer coating.The wear resistance of the coating was at the same level with the wrought and cast materials.展开更多
Influence of Ti/Al ratios on the thermal stability of a new low cost Ni-Fe-Cr base wrought alloy,designed for application at 700℃ in advanced ultra-supercritical coal-fired power plants(700℃A-USC),was investigated b...Influence of Ti/Al ratios on the thermal stability of a new low cost Ni-Fe-Cr base wrought alloy,designed for application at 700℃ in advanced ultra-supercritical coal-fired power plants(700℃A-USC),was investigated both experimentally and thermodynamically. After standard heat treatment,the alloys with different Ti/Al ratios had the same microstructural characteristics. However,compared with the alloys with high Ti/Al ratio,the low Ti/Al ratio can increase the γ’-solvus temperature,decrease γ’ coarsening rate and reduce the temperature range of η phase precipitation. For the alloys with low Ti/Al ratio,the yield strength has no obvious decrease during long-term thermal exposure at 700 and 750℃,but after thermal exposure at 750℃ for 5000 h,the yield strength of the alloys with high Ti/Al ratio obviously decreases due to the η phase precipitation. The influence of h phase on mechanical properties is related with its size. When the h phase is small,it has no obvious influence on mechanical properties,but h phase becomes the crack initiation site with the further growth of η phase. It can be concluded that the decrease in Ti/Al ratio can improve the thermal stability to meet the requirement of 700℃ A-USC coal-fired power plants.展开更多
The valence electron structure of martensite in Fe-Co-Cr based high-alloy steel is calculated using the em-pirical electron theory of solids and molecules (EET). The results show that the incorporation of cobalt leads...The valence electron structure of martensite in Fe-Co-Cr based high-alloy steel is calculated using the em-pirical electron theory of solids and molecules (EET). The results show that the incorporation of cobalt leads to a rise in nA from 0.3835 to 0.4684, which enhances the bonding forces between atoms in a-Fe matrix. Meanwhile, the incorporation of Co changes the valence electron structure of segregated structure units formed by C and other alloying elements, and increases nA for the segregated units containing C-Me sig-nificantly, resulting in changing the precipitation behavior of the secondary phases during tempering and strengtheningthe resistance to tempering.展开更多
文摘Appropriate laser cladding processing parameters for a Ni-Fe-Cr based alloy coating with good quality were studied using 3.5 kW diode laser.The characterization of the coating was investigated,and the influence of each parameter was analyzed.The mechanical properties and wear resistance of the coating were compared with the corresponding chemical composition wrought and cast materials.The results showed that a coating with aspect ratio about 3,dilution ratio 8%-10%and wetting angle 35o-50°could be formed with the laser power 1200-1500 W,travelling speed 8-10 mm/s,powder feed rate 16-18 g/min and shield gas flow 15 l/min.The tensile strength of the coating reached 953 MPa which was higher than that of wrought material 918 MPa and cast material 830 MPa.The microhardness of multi-layer coating was higher than that of single layer coating.The wear resistance of the coating was at the same level with the wrought and cast materials.
基金supported by the National High Technology Research and Development Program of China ("863 Program",No.2012AA03A501)the National Natural Science Foundation of China (No.51301171)+1 种基金the National Energy Administration Program of China (No.NY20110102-1)Chinese Academy of Sciences and Sichuan Province Cooperation Program
文摘Influence of Ti/Al ratios on the thermal stability of a new low cost Ni-Fe-Cr base wrought alloy,designed for application at 700℃ in advanced ultra-supercritical coal-fired power plants(700℃A-USC),was investigated both experimentally and thermodynamically. After standard heat treatment,the alloys with different Ti/Al ratios had the same microstructural characteristics. However,compared with the alloys with high Ti/Al ratio,the low Ti/Al ratio can increase the γ’-solvus temperature,decrease γ’ coarsening rate and reduce the temperature range of η phase precipitation. For the alloys with low Ti/Al ratio,the yield strength has no obvious decrease during long-term thermal exposure at 700 and 750℃,but after thermal exposure at 750℃ for 5000 h,the yield strength of the alloys with high Ti/Al ratio obviously decreases due to the η phase precipitation. The influence of h phase on mechanical properties is related with its size. When the h phase is small,it has no obvious influence on mechanical properties,but h phase becomes the crack initiation site with the further growth of η phase. It can be concluded that the decrease in Ti/Al ratio can improve the thermal stability to meet the requirement of 700℃ A-USC coal-fired power plants.
文摘The valence electron structure of martensite in Fe-Co-Cr based high-alloy steel is calculated using the em-pirical electron theory of solids and molecules (EET). The results show that the incorporation of cobalt leads to a rise in nA from 0.3835 to 0.4684, which enhances the bonding forces between atoms in a-Fe matrix. Meanwhile, the incorporation of Co changes the valence electron structure of segregated structure units formed by C and other alloying elements, and increases nA for the segregated units containing C-Me sig-nificantly, resulting in changing the precipitation behavior of the secondary phases during tempering and strengtheningthe resistance to tempering.
