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Table of Contents

Features
Cold Spray Technology Keeps Historic Aircraft Airworthy . . . . . . . . . .4

Departments
ITSA Member News . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7

On the cover: A historical Lancaster World Industry News . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

War II plane flies in the Royal Dutch Air
Force Open House on June 18, 2005, in Product Spotlight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12
Glize-Rijen, The Netherlands. (Photo by Foto
VDW/DepositPhotos.)
ITSA Membership Directory . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

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By Julio Villafuerte
Feature

Cold Spray Technology Keeps

Historic Aircraft Airworthy

A Lancaster bomber flying over Shoreham Airfield in Sussex, England. (Photo by phil_bird/DepositPhotos.)

T
he Lancaster was a successful British heavy bomber air- ment of machine gun turrets. After the war, surviving Lancast-
craft during World War II. The plane emerged as a re- ers served in various noncombat roles, including patrol, photo
design of the former Avro Manchester aircraft powered by reconnaissance, aerial mapping, flying tanker for aerial refuel-
four 1460 hp Rolls-Royce Merlin engines. The Lancaster first ing, and even as a long range trans-Atlantic passenger and postal
flew in January 1941 and entered production in early 1942. All delivery airliner until they retired around 1960. Today, there are
of the almost 7400 Lancasters produced during the war were about 17 planes remaining in historical static displays, mostly
committed to nighttime strategic bombing. For these missions, in Canada. At least two of those Lancasters have been restored
the plane’s spacious bomb bays typically carried a mixed load of for airworthiness with plans to continue maintaining them
powerful bombs. Most Lancasters were armed with an assort- this way.

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Restoration Challenges
A Maintaining airworthiness on the Lancaster and other histor-
ical airplanes is challenging, at best, due to the lack of spare
parts and/or effective repair and restoration processes available.
Corrosion typically takes a toll on the aesthetics and functionali-
ty of components, many of which are made of treated materials
that cannot tolerate elevated process temperatures. One such
component is a ring belonging to the mounting assembly of the
rear gun turret — Fig. 1. Years of corrosion have created
through-thickness holes affecting both aesthetics and the in-
tegrity of the assembly. These holes are difficult to restore using
conventional thermal processes without affecting the integrity
of the part.

Fig. 1 — A — Rear gun turret (Photo by Paulspixs/DepositPho-

tos); B, C — part of a heavily corroded turret mounting assem-
bly showing through-thickness corrosion holes. (Photos B and Fig. 2 — Commercial SST Series P cold spray manual system.
C are courtesy of CenterLine Windsor Ltd.) (Photo courtesy of CenterLine Windsor Ltd.)

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Table 1 — Spray Parameters

Machine: SST Series P, manual gun, 2.0-mm orifice, UltiLife™ nozzle

Spray Powder: SST A0050 (aluminum — alumina)

Substrate: Heat-treated steel

Gas: Nitrogen

Surface Preparation: Grit blasting with Grit 80

Gas Temperature: 400°C

Gas Pressure: 180 lb/in.2 (13 bar)

Cold Spray Restoration

Cold spray is a solid-state metal consolidation process that
uses a high-speed gas jet to propel metal and other powder par-
ticles against a substrate where particles plastically deform and
consolidate upon impact. The term cold spray refers to the rela-
tively low temperature involved in the process, which is typically
much lower than the melting point of the spray material and
substrate. In cold spray equipment, air can be used as a propel-
lant gas and temperatures will be low enough not to thermally
disturb the substrate material. After low-temperature dimen-
sional restoration of the area, the new consolidated material can
be effectively machined back to tolerance using standard ma-
chining techniques. Cold spray technology offers the ability of
all-metal consolidation for dimensional restoration of manual or
robotic applications — Fig. 2.

The Solution
The steel ring was submitted for cold spray repair. First, sur-
face preparation consisted of cleaning and grit blasting. Then,
cold sprayed aluminum composite was utilized to manually fill in
Fig. 3 — The component cold sprayed and grinded. (Photo all repair areas, including through holes, using the spray parame-
courtesy of CenterLine Windsor Ltd.) ters shown in Table 1. To successfully fill in through-thickness
holes with acceptable adhesion, a qualified cold spray operator
used a step process consisting of slow buildup around the edges
followed by grinding off to prepare the next buildup. The de-
posits were gradually bridged to close the hole. By repeating
Since adhesion of the metal these steps, the good adhesion deposits were warranted for final
powder to the substrate and post-spray grinding — Fig. 3.

deposited material is Conclusion

achieved in the solid state, the Since adhesion of the metal powder to the substrate and de-
characteristics of cold spray posited material is achieved in the solid state, the characteristics
of cold spray deposits are quite unique, making cold spray suit-
deposits are quite unique, able for depositing well-bonded, low-porosity, oxide-free de-
posits. These attributes make cold spray uniquely suitable for
making cold spray suitable depositing a range of temperature-sensitive materials in this
application.
for depositing well-bonded,
low-porosity, oxide-free Julio Villafuerte (julio.villafuerte@cntrline.com) is corporate
deposits. technology strategist at CenterLine Windsor Ltd., Windsor,
Ontario, Canada.

6 SPRAYTIME / First Quarter 2021