Abrasion resistance of surface-modified steels used for artillery weapon barrels
A barrel is one of the most tribologically and thermally loaded parts of artillery weapons. The influence of the salt bath nitrocarburizing and hard-chrome plating of three steels used for artillery barrels on their abrasion resistance is studied in this paper. The tested steels are 42CrMo4, 30CrNiMo8, and 36CrNiMo4 in the initial quenched and tempered state. The test results from the ''dry sand/rubber wheel'' method, after 700 m of wear path, showed that the hard-chrome plating of 42CrMo4 and 30CrNiMo8 steels improved their abrasion resistance. In addition, reduced abrasive wear of 42CrMo4 steel samples was also achieved by nitrocarburizing. Hard chrome-plated samples exhibited good wear resistance due to their greater hardness and bigger thickness of the compound zone in comparison with that obtained on nitrocarburized samples.
INFLUENCE OF ARTILLERY WEAPON BARREL SUPERHEAT ON EROSION WEAR RESISTANCE OF MATERIAL
This paper studies the influence of the artillery weapon barrel superheat on abrasion wear resistance of material. The firing process has a compound mechanical, thermal and chemical effect on the barrel. Many wear mechanisms exist in the barrel in firing conditions: abrasion, adhesion, fatigue and tribocorrosion. This paper presents the procedure and the results of abrasion wear experiment. Some test samples were tempered previously and air cooled. The abrasion test samples were made of the heat treated steel 42CrMo4. Wear resistance is represented by the sample mass loss during the wear process. The test results show that unheated samples exhibit higher wear resistance in comparison with heated samples. A significant material wear increase of 43% is shown in the samples which were heated at 900 °C. Conclusively, the test results show that excessive fire causes the weapon barrel to superheat and the material wear resistance to significantly decrease.
EFFECT OF SAMPLE PREPARATION ON WATER TREE RESISTANCE OF XLPE/SEBS BLENDS
The effects of an aromatic polymer, such as poly[styrene-b-(ethylene-co-butylene)b-styrene] (SEBS), and its preparation processes on water tree resistance, morphology, crystallinity, dielectric constant and dielectric loss tangent of crosslinked polyethylene (XLPE)/SEBS and XLPE/SEBS/ethylene vinyl acetate (EVA) blends were investigated. The XLPE/SEBS samples were characterized by means of differential scanning calorimetry, scanning electron microscopy, dielectric spectral analysis and the accelerated water treeing experiment. The results clearly showed that although SEBS was partially compatible with LDPE and it was dispersed evenly in XLPE matrix, the blends demonstrated excellent dielectric performances, such as dielectric constant and dissipation factor. The crystallinity of XLPE/SEBS blends was decreased with increase in SEBS content and it was further decreased with the addition of EVA. SEBS could effectively improve the water-tree resistance of XLPE and both SEBS and EVA were found to improve the water tree resistance of XLPE synergistically as expected. The differences in sample preparation processes could change the phase morphology and dielectric performance of the blends, and could also influence the dispersion of SEBS in XLPE matrix as well as the crystallinity of the blends. Different preparation processes led to different water tree resistance behaviours of the samples. The improvement of SEBS dispersion in XLPE matrix helped to improve the water tree resistance of XLPE.