Ni/ （10NiO-NiFe2O4） cermets were fabricated by using cold pressing-sintering method. The phase composition and effect of metallic content on the mechanical properties such as bending strength, Vickers’ hardness, fr...Ni/ （10NiO-NiFe2O4） cermets were fabricated by using cold pressing-sintering method. The phase composition and effect of metallic content on the mechanical properties such as bending strength, Vickers’ hardness, fracture toughness and thermal shock resistance were studied. The results show that the cermets consist of Ni, NiO and NiFe2O4. Within the range of metallic content from 0 to 17%（mass fraction）, the relative density decreases with the increase of metallic content and the decrease of sintering temperature, Vickers’ hardness decreases from 7097MPa to 4814MPa and the bending strength increases from 110MPa to 157MPa, and the fracture toughness reaches the optimal value of 5.11MPa·m 1/2 at the metallic content of about 10%. The residual strength after thermal shock testing falls sharply as the thermal shock temperature difference is above 200℃.The cermets samples, whose metallic content is 10% and 15%, respectively, exhibit promising property of thermal shock resistance at 960℃ with six cycles of heating and quenching testing.展开更多
Reliability and wear resistance of cutting picks play a significant role in coal mine exploitation with coal shearers.Tool bit separation,blade breaking,severe erosion of the cutting body and fatigue fractures are the...Reliability and wear resistance of cutting picks play a significant role in coal mine exploitation with coal shearers.Tool bit separation,blade breaking,severe erosion of the cutting body and fatigue fractures are the main reasons for failure of cutting picks.We carried out carburization on a 30CrMnMo alloy to synthesize a new cutting pick material with improved mechanical properties and high wear resistance.The results indicated that carburization can effectively strengthen the surface of the 30CrMnMo alloy by forming a thick carburized layer and thus significantly improve the surface hardness and wear resistance.In addition,the excellent toughness of 30CrMnMo alloy as a substrate of cutting picks can prevent brittle ruptures and fatigue fractures under high impact stress conditions.The significant decrease in both frictional coefficient and rate of erosion of this carburized 30CrMnMo alloy suggests that this alloy is a potential material for cutting picks of coal shearers after rational carburization.展开更多
Lamellar tearing and crack-induced brittle failures along steel plates in the through-thickness direction seriously threaten the safety and reliability of steel thick plate structures in construction and service, espe...Lamellar tearing and crack-induced brittle failures along steel plates in the through-thickness direction seriously threaten the safety and reliability of steel thick plate structures in construction and service, especially at low ambient temperatures. Three kinds of tests, including uniaxial tensile tests, Charpy V-Notch impact tests, and three-point bending （TPB） tests were performed at normal and low temperatures to investigate the through-thickness mechanical properties, impact and fraclure toughness of Q345B structural steel plates with thicknesses from 60 to 165 mm. The test specimens were mainly sampled along the through-thickness direction of the plate, but transverse specimens along the rolling direction were also involved. The ductility index （percentage reduction of area）, impact toughness index （Charpy impact energy）, and fracture toughness index （critical crack tip opening displacement （CTOD） values） all decrease as the temperature declines. All the mechanical properties and the impact and fracture toughness along the through-thickness direction are worse than those along the rolling direction. The results also offer experimental support for the determination of an evaluation indicator for structural steel thick plates with through-thickness characteristics.展开更多
基金Project(2005CB623703) supported by the National Key Fundamental Research and Development Programof China pro-ject (50474051) supported by the National Natural Science Foundation of China project (03JJY3080) supported by the Hunan ProvincialNatural Science Foundation
文摘Ni/ （10NiO-NiFe2O4） cermets were fabricated by using cold pressing-sintering method. The phase composition and effect of metallic content on the mechanical properties such as bending strength, Vickers’ hardness, fracture toughness and thermal shock resistance were studied. The results show that the cermets consist of Ni, NiO and NiFe2O4. Within the range of metallic content from 0 to 17%（mass fraction）, the relative density decreases with the increase of metallic content and the decrease of sintering temperature, Vickers’ hardness decreases from 7097MPa to 4814MPa and the bending strength increases from 110MPa to 157MPa, and the fracture toughness reaches the optimal value of 5.11MPa·m 1/2 at the metallic content of about 10%. The residual strength after thermal shock testing falls sharply as the thermal shock temperature difference is above 200℃.The cermets samples, whose metallic content is 10% and 15%, respectively, exhibit promising property of thermal shock resistance at 960℃ with six cycles of heating and quenching testing.
基金the Youth Foundation of China University of Mining & Technology (No.2009A056)the Tribology Science Fund from State Key Laboratory of Tribology at Tsinghua University (No.SKLTKF08A01)+1 种基金the National Natural Science Foundation of China (Nos.50905180 and 51005234)the National Science and Technology Pillar Program in the Eleventh Five-Year Plan Period (No.2008BAB36B02)
文摘Reliability and wear resistance of cutting picks play a significant role in coal mine exploitation with coal shearers.Tool bit separation,blade breaking,severe erosion of the cutting body and fatigue fractures are the main reasons for failure of cutting picks.We carried out carburization on a 30CrMnMo alloy to synthesize a new cutting pick material with improved mechanical properties and high wear resistance.The results indicated that carburization can effectively strengthen the surface of the 30CrMnMo alloy by forming a thick carburized layer and thus significantly improve the surface hardness and wear resistance.In addition,the excellent toughness of 30CrMnMo alloy as a substrate of cutting picks can prevent brittle ruptures and fatigue fractures under high impact stress conditions.The significant decrease in both frictional coefficient and rate of erosion of this carburized 30CrMnMo alloy suggests that this alloy is a potential material for cutting picks of coal shearers after rational carburization.
基金the National Natural Science Foundation of China，the Specialized Research Fund for the Doctoral Program of Higher Education of China
文摘Lamellar tearing and crack-induced brittle failures along steel plates in the through-thickness direction seriously threaten the safety and reliability of steel thick plate structures in construction and service, especially at low ambient temperatures. Three kinds of tests, including uniaxial tensile tests, Charpy V-Notch impact tests, and three-point bending （TPB） tests were performed at normal and low temperatures to investigate the through-thickness mechanical properties, impact and fraclure toughness of Q345B structural steel plates with thicknesses from 60 to 165 mm. The test specimens were mainly sampled along the through-thickness direction of the plate, but transverse specimens along the rolling direction were also involved. The ductility index （percentage reduction of area）, impact toughness index （Charpy impact energy）, and fracture toughness index （critical crack tip opening displacement （CTOD） values） all decrease as the temperature declines. All the mechanical properties and the impact and fracture toughness along the through-thickness direction are worse than those along the rolling direction. The results also offer experimental support for the determination of an evaluation indicator for structural steel thick plates with through-thickness characteristics.
