International Scientific Journals
of Scientific Technical Union of Mechanical Engineering "Industry 4.0"

Heat-resistant composites with a layered niobium-based matrix reinforced with single-crystal sapphire fibers have been obtained. The fibers were grown from the melt by the modified Stepanov method. The composites were prepared by solid-phase technology by diffusion welding of multilayer packages of foils of the Nb–0.1% C and aluminum alloy, interlaid with sapphire fibers in layers of a suspension mixture of Nb powder. The production of fibers, their structure and strength testing procedure are described. The formation of multilayer packets, the structure and results of bending strength tests of composites are presented

In this paper are presented some macrofractographic and microfractographic analysis of welded joint fracture surfaces, respectively welded seam (W), heat affected zone (HAZ) and base metal (BM), of spiral and longitudinal steel welded pipes after conducting the laboratory destructive testing. Destructive testing are conducted to assess the quality of the steel welded pipes and besides the numerical results, the fracture surface of the tested samples offers additional information, very important for assessing the quality of steel welded pipes. Given this, in the paper are treated the macrofractographic and microfractographic analysis (LOM-Light Optical Microscopy and Scanning Microscopy-SEM) of the fracture surfaces of samples which are fractured after destructive testing. The morphology of the fracture surfaces is compared with the numerical results and it concludes that there is a direct correlation between the obtained results and deformation that causes fracture, providing thus additional information for assessing the quality of the welded pipes.