Effects of carburization and subsequent high-current pulsed electron beam irradiation on the microstructure and properties of TiNbZr alloy

This study investigates the synergistic effects of carburization and high-current pulsed electron beam (HCPEB) irradiation on the microstructure and properties of TiNbZr alloys. The phase composition and microstructure of all samples were characterized by x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The surface microhardness, friction and wear properties of all samples after carburization followed by HCPEB irradiation were tested. Experimental results show that a single BCC crystal structure is maintained in all samples. After carburization, carbon segregation occurs at grain boundaries, accompanied by the precipitation of Nb2C carbides. As the holding time increases, the thickness of the carburized layer and the size of the carbides are increased. After HCPEB irradiation, the carbon distribution is homogenized and the coarse Nb2C decomposes into finely dispersed NbC particles. Meanwhile, surface microcracks are introduced in the 5 min holding time sample with subsequent 30 pulses (H5-30P). A maximum hardness of 571 HV is obtained in the carburizing with the 5 min holding time (H5) sample, originating from the combined contribution of interstitial solid-solution strengthening and second-phase precipitation strengthening. After HCPEB irradiation, the hardness of carburized samples is slightly decreased. Wear test results reveal that wear resistance is significantly improved after carburization, with the H5 sample presenting the optimal tribological performance. After HCPEB irradiation, the wear resistance of the NH sample is further enhanced, which is attributed to the homogenization of the carbon distribution and the formation of dispersed nanoscale NbC particles.