Microstructure and Properties of Fe-Cr-C Hardfacing Alloys Reinforced with TiC-NbC

The hypereutectic Fe-Cr-C hardfacing alloys with different contents of TiB_2 and Nb were prepared by selfshielded flux cored arc welding.The microstructure of a series of hypereutectic Fe-Cr-C hardfacing alloys added with various TiB_2 and Nb contents was investigated by using optical microscopy（OM）,scanning electron microscopy（SEM）and X-ray diffraction（XRD）.In addition,their Rockwell hardness,microhardness and resistance to abrasive wear were tested.The results showed that the microstructure of a series of hypereutectic Fe-Cr-C hardfacing alloys consisted mainly of martensite,austenite,primary M7C3 carbides and eutectic M7C3 carbides.With the addition of TiB_2,a new hard-phase TiC was produced in the hardfacing alloys.And in the alloys added with TiB_2 and Nb,a new hard composite phase TiC-NbC was formed.The microhardness of the matrix was improved by adding TiB_2 and Nb,but the effect on the Rockwell hardness of Fe-Cr-C hardfacing alloys was insignificant.The addition of TiB_2 and Nb can also decrease the size of the primary M7C3 carbides and make the primary M7C3 homogeneous.As a result,the reinforced matrix,the more homogeneous primary M7C3 carbides,and the new hard-phase TiC-NbC all improved the wear resistance of Fe-Cr-C hardfacing alloys.

Preparation and scratch test of AlMgB_(14) modified by TiB_2

In this paper, the Al Mg B14 and Al Mg B14–Ti B2 composites were synthesized by means of mechanical alloying and the field-activated and pressure-assisted synthesis process. The effect of temperature and pressure on the purity and property of products was discussed. The results show that the process of preparing Al Mg B14 bulk materials is optimized as follows： synthesis temperature1,400–1,500 ℃, heating rate 100 ℃ min^-1, axial pressure60 MPa, heat preservation 8–10 min, optimum starting powders＇ ratio Al： Mg： B = 0.1915：0.1363：0.6722, and adding excessive 3 wt% Al. The abrasion resistance of Al Mg B14 composites with varying amounts of Ti B2 was studied using single-point diamond scratch tests with loads ranging from 10 to 100 N in 10 N increments. The scratch width increases almost linearly with the applied load and decreases with Ti B2 proportion increasing up to 70 wt%.With its advantages of fast heating, short reaction time,energy conservation, and high purity, this method offers a new way to synthesize Al Mg B14 and Al Mg B14–Ti B2 composites.

Thermoelectric transport properties and structure of Mg_2Si_(0.8)Sn_(0.2)prepared by ECAS under different current intensities

Thermoelectric materials Mg2Si0.8Sn0.2 were sintered under three different conditions including no electricity sintering（NCS）, low electricity sintering（LCS）,and high electricity sintering（HCS）. Thermoelectric performance and microstructure of three group samples were measured and compared. The results indicate that the application of electric current during the sintering process changes the microstructure and significantly increases the density of samples, and increases the electric conductivity and the power factor. The electric current activated/assisted sintering is an effective way to obtain thermoelectric materials with excellent performance.