Jet engine compressor blade

Jet engine compressor blade

Jet engine compressor blade

Keywords Blades, Jet engines, Titanium

The Broaches/Carpenter partnership found a solution to broaching the root form of a jet engine compressor blade made of titanium (Plate 1). The original toolmaker was unable to make a satisfactory broach. With his tools, subsequently scrapped, the engine manufacturer could broach no more than one blade per tool sharpening.

This was a unique, opposite-hand broach, with 800 teeth per side, that was designed to cut at the same time. It was 500in. long, made in segments and lined up in a bar. Three bars on one machine, in side-saddle position, broached the contours of the titanium form.

Nicoletti asked Carpenter to give him some Micro-Melt T-15 alloy with extra hardness, then designed new broaches for the job. One new set of broaches made from T-15 alloy with RC 66 hardness produced 100 parts before sharpening. Another set, made from the same material with RC 68 hardness produced 650 parts. Still, Nicoletti was asking Carpenter to fine tune the alloy for a Rockwell C hardness of 69 and 70 so he could achieve even greater production.

Space age warhead

Broaches, again with help from Carpenter, solved a broaching problem experienced by a US defense contractor making an infrared housing, for an exploding warhead, from a modified T-200 maraging steel. For three years, several tooling specialists tried to make the required broaches. No tooling was capable of producing acceptable parts.

Plate 1 Root form of titanium compressor blade, right, and broach used to shape it

A thin wall on the mounting base would bulge when it was broached, preventing the sensitive optical lens from moving and functioning properly. Further, broaching would misalign holes that were critical to performance of the optical system. Bell mouths at opposite ends of the housing had thin walls that could not suffer any distortion in broaching.

Nicoletti took on the challenge. He designed and made a new broach from Carpenter Micro-Melt T-15 alloy bar stock. He cut it to length, turned it on a lathe, heat treated, checked straightness, ground the OD, and ground the inverted spline. The defense contractor then produced 425 housings with the new broach before resharpening.

Based on experience, the tooling specialist designed and made a special broach from Micro-Melt T-15 alloy that was used on the Waspaloy section of a turbine for a jet engine (Plate 2). The broach was designed with a cam that pushes back on a fixture to broach a key radius.

Plate 2 Button-like extension of this Waspaloy turbine blade, bottom left, is broached

"The Carpenter T-15 alloy gives me the optimum cutting edge", Nicoletti reported. "It has the best edge toughness and edge hardness of any cutting tool material I have ever handled."

Carpenter Micro-Melt T-15 alloy has been used for many types of tooling applications where hot hardness, improved grindability and wear resistance are important. Typical applications, in addition to broaches, have included: form tools, lathe tools, planer tools, milling cutters, blanking dies, punches, drills, screw machine tools and cold work tools.

The alloy's typical analysis is: carbon 1.50 per cent, sulfur 0.06 per cent, chromium 4.75 per cent, vanadium 5.00 per cent, tungsten 13.0 per cent, cobalt 5.00 per cent, balance iron.

For further details contact Harrison Garner at +1 610 208 2932; for more information about broaches, contact Joseph Nicoletti at +1 810 296 2970.

Canadian readers can obtain additional information from Carpenter's Toronto Service Center by calling 1 800 268 4740.