"Metal "tantalum" reduces corrosion in the barrel and increases muzzle velocity"

Table 1. Key properties of barrel liner or coating potential materials

Tantalum and Tantalum-10W and similar alloys have been used as liners and coatings for military powder guns and have been shown to be effective in reducing barrel corrosion.

As can be seen from Table 1, the thermal performance of tantalum is slightly worse than that of rhenium, because the melting point, density and thermal conductivity of tantalum are lower than the corresponding values of rhenium. However, the melting point of tantalum is nearly 90% higher than that of rhenium than that of gun steel. Clearly, tantalum is a strong candidate for the lining/coating of a two-stage light gas gun.

There are four data blocks in Table 2, separated by vertical lines. Data block 1 uses type 4198 powder and the remaining data blocks use type 4895 powder. The first two data blocks have a nominal pump tube volume of 100%, and data blocks 3 and 4 have a nominal pump tube volume of 60% and 40%, respectively. There were also differences in the constriction cone angle between data blocks, as shown in Table 2; these were considered less important than differences in powder type and pump tube volume. The gun configurations for the various data blocks are as follows:

Data block 1: The size is shown in Figure1.

Block 2: The taper angle becomes 8.1°.

All axial dimensions on the right side of data block WG1 have been reduced by 607.22 cm; the taper angle has been changed to 8.1 degrees.

All axial dimensions on the right side of block WG1 are reduced by 911.82 cm; the taper angle is changed to 8.1 degrees.

For the data in blocks 2, 3 and 4 with a taper angle of 8.1 degrees, the axial dimension of the big end of the taper was shifted to accommodate the taper angle.

Table 2 Ames 0.5" gun operating conditions for simulated data blocks

The shots in Table 3 are modeled in different ways. All 45 shots were simulated with a steel barrel with steel added to the hydrogen (denoted as "steel,l" in the table). Thirty-six shots were then simulated with a steel barrel and no hydrogen loading with steel (noted in the table as "steel, no 1").

Rhenium was added to the hydrogen (denoted as "re,l" in the table). Projectiles chosen to be modeled with rhenium barrels are mostly manufactured under high performance artillery operating conditions, where the highest muzzle velocity gain is expected when switching from steel to rhenium barrels.

The nine highest performance shots were remodeled with a tantalum barrel, loaded with tantalum hydrogen (denoted as "Ta,l" in the table).

Table 3 Observed or predicted barrel lengths for erosion

Figure 1 shows the CFD muzzle velocities of steel, rhenium and tantalum tubes versus the experimental muzzle velocities of steel tubes. It can be seen that for 7 of the 9 injections, the results for the tantalum and rhenium tubes are indistinguishable. For the second highest velocity shot, the muzzle velocity of the tantalum tube is slightly lower than that of the rhenium tube (~0.040 km/s). For the highest velocity fire, the muzzle velocity of the tantalum tube is about 0.70 km/s less than that of the rhenium tube, but even so, the muzzle velocity gain produced by the tantalum tube is about 82% of the muzzle velocity gain of the steel tube that can be obtained with the rhenium tube. The conclusion is that, in general, tantalum barrels can produce a significant portion of the muzzle velocity gain obtained with rhenium barrels.

Figure 1 Comparing the CFD muzzle velocity of the Ames 0.5-inch gun with steel, tantalum, and rare earth tubes to the experimental muzzle velocity of the steel tube in 9 high-performance shots of data block 1

Figure 2 shows the relationship between the CFD gun barrel mass loss and the CFD initial velocity of the steel tube, rhenium tube and tantalum tube. Figure 3 shows the same CFD gun barrel mass loss versus the ratio (powder mass)/(hydrogen mass).

The mass loss of tantalum tubes is 0 to 0.14 times that of steel tubes, and the mass loss of rhenium tubes is 0 to 0.05 times that of steel tubes. For the highest velocity data point, the mass loss of refractory metal pipe is 0.25 to 0.45 times that of steel pipe.

Figure 2 Relationship between CFD tube mass loss and CFD initial velocity of steel tube, tantalum tube and rhenium tube for 0.5-inch Ames gun

Figure 3. Computational fluid dynamics tube mass loss versus the ratio of powder mass to hydrogen mass for a 0.5-inch Ames gun for steel, tantalum, and rare earth tubes

Figure 4 shows the computational fluid dynamics curves of the mass loss along the barrel for steel, rhenium and tantalum tubes for 33-93 shot conditions.

Figure 5 shows the corresponding data for lenses 20-80 and Figure 6 . Figure 6 shows the corresponding data for lenses 18-78.

Figure 4 Computational fluid dynamics tube mass loss plotted against distance to gun for 33-93 rounds of Ames 0.5-inch guns for steel, tantalum, and rare earth tubes

Figure 5 CFD tube mass loss of 20-80 for steel, tantalum, and rhenium tubes, and mass loss for Ames 0.5-inch guns as distance along the gun

Figure 6 Computational fluid dynamics tube mass loss plotted against distance from gun for 18-78 rounds of Ames 0.5-inch guns with steel, tantalum, and rare earth tubes