WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravi...WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The effect of sintering temperature on the microstructure and mechanical properties of nanocrystalline cemented carbide was studied by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and mechanical property test.The results showed that the nano WC grains began to grow in the solid phase sintering stage.A high-performance nano-nitrogen-containing cemented carbide with uniform microstructure and good interfacial bonding can be obtained by increasing the sintering temperature to 1380℃.It has a transverse rupture strength(TRS)of 5057 MPa and a hardness of 1956 HV30.展开更多
WC-10Co cemented carbides with finer WC and narrower grain size distributions are produced by using(Cr,V)_(2)(C,N)as grain growth inhibitors.As a result,with the increase of(Cr_(0.9),V_(0.1))_(2)(C,N)and(V_(0.9),Cr_(0...WC-10Co cemented carbides with finer WC and narrower grain size distributions are produced by using(Cr,V)_(2)(C,N)as grain growth inhibitors.As a result,with the increase of(Cr_(0.9),V_(0.1))_(2)(C,N)and(V_(0.9),Cr_(0.1))_(2)(C,N),the grains size of WC and mean free path of Co phase decrease,and adjacency of WC increases.Refinement and homogenization of grains enhance the transverse rupture strength(TRS)and the hardness.Meanwhile,the deflection and bridging of cracks keep the fracture toughness at a respectable level.The WC-10Co-0.6(Cr_(0.9),V_(0.1))_(2)(C,N)-0.025(V_(0.9),Cr_(0.1))_(2)(C,N)cemented carbides exhibit excellent comprehensive mechanical properties with the TRS of 4602.6 MPa,hardness of 1835 kg/mm^(2),and fracture toughness of 10.39 MPa·m^(1/2),respectively.However,the large pores are caused by excess N larger than 0.03 wt%and deteriorates the mechanical properties.We provide a new approach to WC-Co cemented carbides preparation with a narrow grain size distribution by adding novel grain growth inhibitors.展开更多
The isotropic Sm_(2)Fe_(17)N_(x)magnetic powders were prepared by Hydrogenation-Disproportion-Desorption-Recombination(HDDR)process.The phase and microstructure evolutionary process of Sm-Fe alloy during the solidific...The isotropic Sm_(2)Fe_(17)N_(x)magnetic powders were prepared by Hydrogenation-Disproportion-Desorption-Recombination(HDDR)process.The phase and microstructure evolutionary process of Sm-Fe alloy during the solidification,homogenization,HDDR and nitration processes were investigated by means of XRD,SEM,EDX and AFM.The results show that the homogeneous Sm_(2)Fe_(17)alloy was successfully obtained and the impurity phases and residual stress were well removed by heated at 1050℃for 24 h.When heated at 800℃for 1h in H_(2)of 0.1 MPa,the alloy turns into SmHx andα-Fe with plenty of nanocrystals.After vacuumized at 800℃for 2 h the alloy recombines into Sm_(2)Fe_(17)with a crystal grain size of about 85 nm.The lattice constant of the alloy increases and the expanding of the crystal cell reaches 6.28%after nitrified at 500℃for 5 h.The magnetic property of isotropic bonded Sm_(2)Fe_(17)N_(x)magnets is B_(r)=0.6704 T,H_(cj)=1015 kA·m^(-1),(BH)_(max)=73.7 kJ·m^(-3)with a density of 6.04 g·cm^(-3).展开更多
基金Funded by the National Key Research and Development Plan of China(No.2017YFB0305900)。
文摘WC-Co nanocrystalline nitrogen-containing cemented carbides were prepared by vacuum sintering and low pressure sintering.The sintering processes of Cr_(2)(C,N)doped nano WC-Co powders were studied by using thermogravimetric analysis(TGA)and differential scanning calorimetry(DSC).The effect of sintering temperature on the microstructure and mechanical properties of nanocrystalline cemented carbide was studied by scanning electron microscope(SEM),high resolution transmission electron microscope(HRTEM)and mechanical property test.The results showed that the nano WC grains began to grow in the solid phase sintering stage.A high-performance nano-nitrogen-containing cemented carbide with uniform microstructure and good interfacial bonding can be obtained by increasing the sintering temperature to 1380℃.It has a transverse rupture strength(TRS)of 5057 MPa and a hardness of 1956 HV30.
基金Funded by the 2021 Strategic Cooperation Project between Sichuan University and The People's Government of Zigong(No.2021CDZG-1)Major Science and Technology Research Projects of Panxi,Sichuan Province(No.2022PXZB-04)。
文摘WC-10Co cemented carbides with finer WC and narrower grain size distributions are produced by using(Cr,V)_(2)(C,N)as grain growth inhibitors.As a result,with the increase of(Cr_(0.9),V_(0.1))_(2)(C,N)and(V_(0.9),Cr_(0.1))_(2)(C,N),the grains size of WC and mean free path of Co phase decrease,and adjacency of WC increases.Refinement and homogenization of grains enhance the transverse rupture strength(TRS)and the hardness.Meanwhile,the deflection and bridging of cracks keep the fracture toughness at a respectable level.The WC-10Co-0.6(Cr_(0.9),V_(0.1))_(2)(C,N)-0.025(V_(0.9),Cr_(0.1))_(2)(C,N)cemented carbides exhibit excellent comprehensive mechanical properties with the TRS of 4602.6 MPa,hardness of 1835 kg/mm^(2),and fracture toughness of 10.39 MPa·m^(1/2),respectively.However,the large pores are caused by excess N larger than 0.03 wt%and deteriorates the mechanical properties.We provide a new approach to WC-Co cemented carbides preparation with a narrow grain size distribution by adding novel grain growth inhibitors.
文摘The isotropic Sm_(2)Fe_(17)N_(x)magnetic powders were prepared by Hydrogenation-Disproportion-Desorption-Recombination(HDDR)process.The phase and microstructure evolutionary process of Sm-Fe alloy during the solidification,homogenization,HDDR and nitration processes were investigated by means of XRD,SEM,EDX and AFM.The results show that the homogeneous Sm_(2)Fe_(17)alloy was successfully obtained and the impurity phases and residual stress were well removed by heated at 1050℃for 24 h.When heated at 800℃for 1h in H_(2)of 0.1 MPa,the alloy turns into SmHx andα-Fe with plenty of nanocrystals.After vacuumized at 800℃for 2 h the alloy recombines into Sm_(2)Fe_(17)with a crystal grain size of about 85 nm.The lattice constant of the alloy increases and the expanding of the crystal cell reaches 6.28%after nitrified at 500℃for 5 h.The magnetic property of isotropic bonded Sm_(2)Fe_(17)N_(x)magnets is B_(r)=0.6704 T,H_(cj)=1015 kA·m^(-1),(BH)_(max)=73.7 kJ·m^(-3)with a density of 6.04 g·cm^(-3).
