That’s fair enough. It would be interesting to know what the various substitutes were for high-temperature chrome-alloy steel, high-strength molybdenum steel, nickel-chrome alloys, copper-nickel alloyed aluminium and so in on demanding applications, and why these substitute materials were not kept in use after the war.
Most of the difficulty i have with this is that combat aero engines are by definition ‘very high performance devices’, and everywhere I look I see things like “Two intake and two exhaust valves per cylinder. Stellite-faced sodium-cooled nichrome-alloy valves.” for the V-1710
So just there we have nickel, cobalt, chromium and no doubt a bunch of other trace elements. Basically the same for the Merlin/V-1650, Molybdenum steel crankshaft. High-strength aluminium alloys with more copper and nickel.
I have just read an article published 1937 that talks about R-Rs use of hiduminium alloys, I would assume other manufacturers did similar. Stellite was in use during that period as well. These materials are mentioned over and over again, and they are expensive even today but I have never seen anything to indicate that these materials were taken out in favour of substitutes, even temporarily.
Also, many of these engines continued in use post-war. One would expect to see either any wartime substitutes retained (if they were equivalents or superior), or copious warnings relating to the use of wartime parts (if they were inferior), or if it was a cost issue then some mention of “the good old days” when wartime budgets allowed the use of better materials. But I have never seen any such, even though people are flying all various WW2 aircraft today and have to demonstrate they are compliant with a mountain of engine safety regulations.
That's because for the most part, the savings weren't achieved by using substitutes for alloys where it mattered, and in many cases the substitutes weren't as good as the high-end alloys anyway. In some cases methods were found to make the substitutes as good without alloys (like good cast tank armor with only .5% nickel), but in most cases the savings came from eliminating waste, eliminating alloys from areas where they were unnecessary, or redesigning components so that they experienced less extreme conditions or were inherently stronger and thus didn't need the alloys. Though it may not appear that way, those methods continued to be used post-war. There are some examples that are not from aircraft engines but were likely applicable to them (and most likely used at least in the US if not elsewhere). First, from
a presentation on the EMD 567's development:
The 567 exhaust valve was first made of 15% chrome, 15% nickel Alloy similar to the 201A valve, but it was thought that a Stellited seat face would give longer life
....
In 1942 the valve material was changed to a 21% chrome, 12% nickel for the head and lower stem, with a hardenable alloy steel upper stem to provide better scuff resistance in the stem and to reduce the nickel and chrome use. The 2112 also provided better seat face hardness of 25 Rockwell "C". To prevent wear at the tip of the stem a hard cap was originally used, but in 1946 the tip of the alloy steel stem was flame hardened and the cap was eliminated. These material and hardness modifications to the original design have resulted in a good service life for the valve.
(p. 43-44)
This represents an elimination of alloy from an area where it is unnecessary, as the high temperatures and wear occur only on the valve head and the alloys in the stem are largely wasted. So instead of making an entire component out of exotic alloys it was split into parts so only the components that needed to be made of such alloys were made of them (this is not always effective and sometimes can increase strategic materials use, but in this case it worked). This can also be seen in one of the sources in a previous comment, where copper bullet jackets were electroplated rather than pressed on, enabling much thinner copper jackets and considerable savings (as only the very outermost microscopic layer actually needed to be hard to engage the rifling and the inner layers were largely wasted).
The next one is on bearings:
During World War II it was necessary that we change all main bearings to solid lead bronze with lead tin coating because of material shortages on steel tubing. During the war, methods were developed to make the lead bronze bearings by casting on rolled steel strips butt welded, the split line then cut through the weld. The steel back lead bronze bearing then supplanted the solid bronze bearing which was subject to fatigue failure.
(p. 54)
This represents an elimination of steel tubing due to more efficient manufacturing methods that do not rely on steel tubing (and likely less steel in total).
The final example is on pistons:
In the early days of the war Electro- Motive was chosen to build the 184 Pancake engine. This engine had a fabricated steel piston into which was bolted two trunnion-like parts that carried the wrist pin. The piston was very symmetrical and had the advantage that the piston pin bosses were not connected into the skirt in any way. The appearance of this piston was excellent and all of the test data indicated it was a very successful design. In an attempt to copy the 184 design we ran into some basic difficulties, the principal one being that it was im- possible to bolt the trunnions into a design similar to the 184 because the piston cooling jet location was exactly where the bolt should go. A number of waste baskets were filled with drawings trying to design our way out when one day someone made the very simple suggestion, "Why not make the piston pin bosses part of the baffle and pilot it at the top and bottom and retain it with a snap ring?". Calculations indicated that the snap ring would be considerably stronger than any bolts or capscrews which could be applied. To simplify machining, another suggestion was made that the upper pilot be made round rather than using dowels or other methods of location. This meant the piston was free to rotate about the carrier and could be perfectly symmetrical so that upon expansion it would retain its original round shape.
The original design of the floating piston was fabricated steel (Fig. 22). We thought that the elimination of a casting in this vulnerable spot would be an
advantage. Because we could not analyze the stresses occuring in the crown and skirt due to thermal stresses as well as the peculiar shape of the crown, it was decided to make a cast design on which it would be easy to change the location of the load carrying members and thus develop the optimum location. On the second steel design the skirt fell off after a short time. This proved we needed the conical member from the platform into the ring belt that was incorporated in the first design.
The cast design had struts tying the platform into the ring belt based on the above experience (Fig. 23).
The first floating piston was cast in a medium grade cast iron as we wanted the weak points to show up fairly quickly. This design piston was run in a 16 cylinder engine for a considerable length of time with no failures. In fact, when asked to run some special high output tests for the U.S. Navy the engine with these floating pistons was used and run over 400 hours at 2000 B.H.P. and a total of 24 hours at 2250 HP. After this Navy test the pistons were inspected and found to be in excellent condition.
(p. 26-29)
This represents an elimination of a fabricated or cast steel section by redesigning the part to reduce the conditions on a single section (the section near the piston pin bosses), and enabling lower-strength cast iron to be used.
There are some other postwar experimental improvements to this effect, mainly the design enabling an increase in wrist piston pin area from 10 to 22 square inches and an increase in lifespan without any more exotic materials.
The final and most important method was to reduce waste in manufacturing. This was applied in particular to guns (the stamped guns and the use of hammer-forged or cold-swaged barrels, plus methods used to make the Bofors more efficiently mentioned in a source on my previous post), but it was useful in engines and exotic alloys in particular. While WWII aircraft engine results are harder to find, there are plenty of postwar sources about waste in strategic alloys, especially
one 1983 source about the use of titanium in aircraft and aircraft engines:
Titanium Alloy Utilization for a Typical Modern Fan-Jet engine:
| Alloy | Form | Finished part weight (lbs) | Raw Material weight (lbs) | Percent used finished/raw wt. |
|---|
| Ti | Sheet | 142.2 | 210.0 | 67.7 |
| "" | Bar and forging | 27.8 | 299.4 | 9.3 |
| 5Al-2.5Sn | Sheet | 121.2 | 256.8 | 47.2 |
| "" | Bar | 5.3 | 64.7 | 8.2 |
| "" | Forging | 183.6 | 2,366.4 | 7.8 |
| 6Al-4V | Bar and forging | 223.8 | 1,544.0 | 14.5 |
| Al-1Mo-1V | Bar | 2.0 | 15.3 | 13.1 |
| "" | Forging | 238.0 | 1,152.8 | 20.6 |
| Total | | 944.3 | 5,909.4 | 16.0 |
(p. 112)
Estimated Purchase and Fly weights of Titanium Components in Aircraft Gas Turbine Engines:
| Engine | Purchase Weight (lb) | Fly Weight (lb) | Airframe | % used finished/raw wt. |
|---|
| J52 -P-6 | 1,300 | 300 | A-4E/F/M | 23 |
| J52-P-8A | 1,400 | 300+ | A-6A/B/E | 21.4+ |
| J79-8 | 600 | 125 | F-4J/M | 20.8 |
| J79-15 | 500 | 100 | RF-4C/D/E | 20 |
| TF30-P-6 | 4,500 | 850 | A-7A | 18.9 |
| TF30-P-3/8 | 4,500 | 850 | F-11A/B, F-14A | 18.9 |
| TF41-A-1 | 1,200 | 285 | A-7D/E | 23.8 |
| J58 | 4,000 | 800 | YF-12A | 20 |
| TF33-P-7 | 4,250 | 637 | C-141A | 15 |
| TF33-P-5 | 3,800 | 565 | C-135B | 14.9 |
| J75-P-19W | 4,500 | 677 | F-105 | 15 |
| TF-39 | 8,000-9,000 | 2,100 | C5A | 23.3-26.3 |
| T-76 | 150 | 25 | OV-10A | 16.7 |
| TF-34 | 1,200 | - | A-10A | - |
| J85 | 500 | 60 | F-5, T-38A | 12 |
| F-100/401 | 5,500 | - | F-15, F-16 | - |
| J101 | 1,400 | - | F-18 | - |
| F101 | 4,500 | - | B-1 | - |
| T-64 | 800 | - | CH-53E | - |
| T-701-700 | 1,000 | - | - | - |
| JT9D | 12,000 | 1,200-2,300 | B-747 | 10-19.2 |
| CFG-50 | 8,000 | 700-1,300 | DC-10 | 8.75-16.3 |
| RB-211 | 5,500 | - | L-1011 | - |
| GE-4 | - | 1,000 | B-2707 (SST) | - |
(p. 113)
Estimated Purchase and Fly Weights of Titanium in Airframes of Commercial Airliners:
| Aircraft System | Purchase Weight (lb) | Fly Weight (lb) | % used finished/raw wt. |
|---|
| 707 | 500 | 190 | 38 |
| 727 | 1,800 | 750 | 41.6 |
| 737 | 3,200 | 1,100 | 34.4 |
| 747 | 32,000 | 11,000 | 34.4 |
| 747SP | 45,000 | 12,000 | 26.7 |
| 757 | 35,000 | 9,500 (not final) | 27.1 |
| DC-9-30 | 2000 | 600 | 30 |
| DC-8-62 | 10,000 | 2,426 | 24.5 |
| DC-10-30 | 30,000 | 8,100 | 27 |
| L-1011 | 31,600 | 14,000 | 44.3 |
(p. 114)
Mill Product Forms for the F-14 and F-15 (purchase weight):
| Form | Estimated amount in F-14 (lbs) | Form | Estimated amount in F-15 (lbs) |
|---|
| Forgings | 22,400 | Forgings | 29,150 |
| Plate | 12,000 | Plate | 11,000 |
| Sheet | 4,400 | Sheet | 5,200 |
| Bar and tubing | 1,200 | Extrusions, tubing, and fasteners | 11,350 |
| Total | 40,000 | Total | 56,700 |
| Estimated fly weight | 5,190 | Estimated fly weight | 6,940 |
| Percent of purchase weight | 13 | Percent of purchase weight | 12.1 |
(p. 115)
Estimated Purchase and Fly Weights of Titanium in Airframes of Military Airframes:
| Aircraft System | Purchase Weight (lb) | Fly Weight (lb) | % used finished/raw wt. |
|---|
| A4M | 150 | 50 | 33.3 |
| A-6E | 600 | 185 | 30.8 |
| A-7E | 280 | - | - |
| F-4J/M | 2,800 | 1,200 | 42.9 |
| F-5E/F | 750 | - | - |
| A-10A | 2,600 | - | - |
| F-16 | 3,000 | - | - |
| F-18 | 6,000 | - | - |
| C-130H | 1,000 | - | - |
| B-1 | 170,000 | 24,800 | 44.3 |
(p. 116)
In WWII and earlier, it seems that closer to 95-99% of raw materials in high-end applications ended up as waste in the production process. The reduction of this is where most of the savings in US industry occurred, and the amount of improvement possible meant that it was possible to match or exceed other nations' reductions without changing the product much. These kinds of improvements dominate the previous sources I mentioned on WWII US industry, and account for the majority of savings. This continued after the war to a small degree with things like the J65's diffuser housing being manufactured differently, and in the 1980's with
a process known as Gatorizing for reducing jet engine raw materials use (from 2,000 to 785 lbs).
So there may be no noticeable difference in the final product, but the amount of material used was vastly reduced using those methods without loss of performance and there were no noticeable changes before or after the war because the parts were no different in performance.
