EFFECT OF BORON ON THE WEAR BEHAVIOR OF HIGH CHROMIUM WHITE CAST IRONS

The wear behavior of high chromium white cast irons with composition: 2,6÷3,4% C; 0,9÷1,1% Si; 0,8÷1,1% Mn; 1,0÷1,3% Mo; 12,3÷13,4% Cr and 0,18 ÷ 1,25% B is investigated. The microstructure and tribological characteristics of six compositions of high chromium white cast irons (one without boron and with 0,18; 0,23; 0,59; 0,96; 1,25% boron) are studied.After casting, heat treatment was carried out, including quenching at 9500C and tempering at 2350C for 1 h. The influence of the heating temperature in the interval 850÷11000С, 25 min on the Rockwell hardness and the microstructure are studied.The wear resistance during abrasive wear for samples after casting and after heat treatment is investigated as measured loss of mass in terms of dry friction under load of 1,5 kg during 10 min. The lowest mass loss during abrasive wear test in dry conditions friction is defined for cast irons alloyed with 0,18 % boron - ∆ m = 0,1469 g after casting and ∆ m = 0,0022 g after heat treatment. The highest mass loss is determined during abrasive testing of alloyed cast irons with 0,96 and 1,25% boron. The alloyed cast irons with 0,18 % boron show highest wear resistance.

Fabrication and Characterization of Aluminum-Graphene Nano-Platelets—Nano-Sized Al₄C₃ Composite

Reinforcement of aluminum and aluminum alloys with graphene has been intensively practiced by researchers in the past dozen years. The role of Al4C3, which could be produced unintentionally or purposefully during the composite production, was controversial until it was found that nano-sized carbides were beneficial for strengthening the composites. aluminum-graphene-nano-sized Al4C3 composites were produced by us using the powder metallurgical method and subsequent annealing. The microstructure was investigated using light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and high resolution transmission electron microscopy HRTEM. Nano-sized carbides were found at the interface aluminum-graphene. The formation of a chemical bond between aluminum and graphene during annealing was proved. Lower values of the microhardness and strength characteristics of the composites after extrusion and subsequent annealing during which nano-sized carbides are formed were found in comparison with those obtained after extrusion. It could be supposed that the annealing processes contribute more to the reduction in microhardness and strength characteristics than nano-sized carbides contribute to its increase. The presence of a strong chemical bond between the graphene and the aluminum is manifested in the failure pattern, which is characterized by graphene nano-platelets and nano-sized carbides fracture and semi-pulled out or semi-slipped Al4C3 from the matrix

Fabrication and Characterization of Aluminum-Graphene Nano-Platelets—Nano-Sized Al4C3 Composite

Reinforcement of aluminum and aluminum alloys with graphene has been intensively practiced by researchers in the past dozen years. The role of Al4C3, which could be produced unintentionally or purposefully during the composite production, was controversial until it was found that nano-sized carbides were beneficial for strengthening the composites. aluminum-graphene-nano-sized Al4C3 composites were produced by us using the powder metallurgical method and subsequent annealing. The microstructure was investigated using light microscopy (LM), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), transmission electron microscopy (TEM), and high resolution transmission electron microscopy HRTEM. Nano-sized carbides were found at the interface aluminum-graphene. The formation of a chemical bond between aluminum and graphene during annealing was proved. Lower values of the microhardness and strength characteristics of the composites after extrusion and subsequent annealing during which nano-sized carbides are formed were found in comparison with those obtained after extrusion. It could be supposed that the annealing processes contribute more to the reduction in microhardness and strength characteristics than nano-sized carbides contribute to its increase. The presence of a strong chemical bond between the graphene and the aluminum is manifested in the failure pattern, which is characterized by graphene nano-platelets and nano-sized carbides fracture and semi-pulled out or semi-slipped Al4C3 from the matrix