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.
Gas–metal reaction products in the erosion of chromium-plated gun bores
Abstract While the general mechanisms in the erosion of gun bore surfaces are known to include coating spallation, gas–metal reactions, and melting, many of the details are issues of considerable uncertainty and debate. The present report addresses one of these issues, the origins of the loss of the protective chromium coating. A survey study was conducted on erosion damage in chromium-plated gun bore surfaces using specimens of three erosion-damaged, chromium-plated, 120-mm M256 gun barrels and two erosion-damaged, 155-mm gun barrels (M199 and XM297). Specimens were examined by optical microscopy, laser scanning confocal microscopy (LSCM), and electron microprobe analyses. New insights regarding the erosion process and the origin of chromium loss were obtained from analyses of the initial damage to the steel at the tips of the fine cracks in the chromium. Products from gas–metal reactions at the gun bore surface are usually difficult to find because of gas wash effects. Observations on unetched specimens revealed that these products remain in place in the relatively protected regions beneath the chromium when chromium crack widths are small. The initial damage from gas–metal reactions is manifested optically as gray layers or gray reaction zones in the steel at the tips of the fine chromium cracks.
Anomalous Annealing Behavior of Arsenic Implanted Silicon as a Function of Dose and Energy
Anomalous annealing behavior of damage in As implanted Si has been investigated by channeling effect measurements. Room temperature As implants with doses from 1014 to 2 × 1016cm-2 at energies ranging from 50 to 250 keV into Si were annealed over the range of 600°C to 1100°C. Anneal temperatures ≥ 950°C reduce the disorder for ion doses of 0.5 to 1 × 1016 cm-2 at energies between 50 and 250 keV. Anomalously high residual disorder was found for the intermediate doses of 2 × 1014 to 2 × 10/cm2 implanted above 100 keV. For this intermediate dose, annealing of implants performed at liquid nitrogen temperatures did not show significant reduction in this damage. However implants at 200° to 300°C indicate a lower amount of damage compared to the room temperature implants.