engleski

Influence of Artillery Weapon Barrel Superheat on Erosion Wear Resistance of Material

This paper studies the influence of the artillery weapon barrel superheat on erosion wear resistance of material. A great quantity of powder gases are produced in the weapon barrel the when weapon fires. The temperature of these gases reaches up to 3700 K, and their maximum pressure is up to 7000 bar. The powder gases have a compound chemical composition, so they create a very aggressive atmosphere in relation to the barrel material. At the same time, the powder gases also contain solid particles: soot particles and unburned powder grains. These particles move with great speed in the strong turbulent streaming of the powder gases. In this way, the erosive wear of the barrel material appears on the bore surface. This is the erosive wear of material caused by solid particles. At the same time, the contact pressure on the rotating band and the barrel bore surfaces appears. It results in a normal force effect on the contact surfaces, so a strong sliding friction force is generated on these surfaces. Energy produced by sliding friction transforms to heat energy too, so the barrel material heating is very intensive in such firing conditions. Therefore, the rate of fire is determined for every artillery weapon to keep the barrel heating on the allowed level. The test sample production was based on the previous analysis of some weapon barrel materials. So, the erosion test samples were made of the heat treated steel 42CrMo4. This steel has similar chemical, metallographic and mechanical properties as the analysed weapon barrel steel. The test samples were tempered at 600 °C, 700 °C, 800 °C, and 900 °C over a period of one hour and then air cooled. It is the way of heating and cooling similar to the superheating and cooling of the barrel during intensive firing. Wear resistance is represented by the sample mass loss after 15, 30, 45, and 60 minutes of erosion wear time. The test results show that unheated samples exhibit higher wear resistance in comparison with heated samples. Wear resistance increases as many as 3.9 times if the material was previously heated at 600 °C. The heating of material at 700 °C and 800 °C causes more intensive material wear. A significant material wear increase is shown in the samples which were heated at 900 °C. The samples heated in this way represent as many as 17.5 times greater material loss than the unheated samples. The test results show that adherence to the determined fire rate is very important: excessive fire causes the weapon barrel to superheat as well as a significant decrease in the material wear resistance.

weapon barrel; fire rate; superheat; erosion

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