High fuel prices, stricter emissions regulations, and intense competition from low-cost carriers are driving a quest for more efficient aero-engines and components, and even small advantages can drive major benefits.

Turbine blades are no exception, according to a recent report by Market Research Future suggesting that the market for commercial aircraft turbine blades is set to grow at a compound annual growth rate (CAGR) of 6% by 2023.

The casting industry is investing to meet this demand and looking to gain advantages in every aspect of manufacture, including for the support rods used in the production of turbine engine blades. The two most commonly used materials to cast these are quartz (silica) and alumina.

Quartz, the traditional material of choice, is chemically weak and fast to leach, which accelerates and simplifies production. On the other hand, its mechanical weakness can lead to processing issues and defects during investment casting of difficult metals such as super-alloys.

Alumina rods have about 4x the mechanical strength of quartz and have high strength and load-bearing capabilities. However, alumina is so chemically strong it can take several days to fully leach out the material, resulting in longer production times.

While the two materials offer almost opposite properties, they share one common advantage: neither create trace elements that can contaminate processes or compromise part quality and performance.

Neither material is perfect, but what if there was a way to combine the best properties of each?

Making LEMA

Following significant experimentation, the solution lay in combining two materials in the right balance – a complex task, especially as the materials in question were so different.

Morgan’s laboratories started with a method borrowed from glass science – using two distinct phase-separate materials to improve mechanical properties such as toughness or to provide a leaching path through the chemically weaker glass. Ultimately, the laboratories created an alumina-silicate ceramic with a leaching path of silica across the grain boundaries. Adjusting particle size distribution and processing parameters produced the desired mechanical strength. LEMA entered the market in 2017.

Fast leaching, no strength loss

LEMA is almost 2x as strong as quartz and has a slightly lower thermal expansion coefficient than alumina, which can help with metal leakages sometimes encountered with alumina rods during casting. Made of pure materials, LEMA satisfies the requirement for trace-element certification.

LEMA crumbles out when flushed, making it easier to remove during leaching. Moreover, LEMA 250 parts will experience approximately a 20% mass reduction after 20 hours at 300°F (149°C) and 185psi. Under the same conditions, a comparable alumina part does not demonstrate any mass loss.

In addition to its advantageous chemical and mechanical properties, LEMA can reduce investment casting times in turbine engine blades by accelerating leaching by up to 20%, solving many delays and production challenges.

Less need for autoclave time during the leaching process spares manufacturers some of the costly investment in additional equipment.

LEMA offers a powerful solution for the investment casting of turbine blades, just as the industry is facing an increased demand for these critical components. Combining the best aspects of quartz and alumina represents the best of both worlds as well as a major breakthrough for the industry.

Morgan Advanced Materials

http://morganadvancedmaterials.com

Miniaturization and/or lightweighting typically demands higher dimensional accuracy and surface finish and increased use of difficult-to-machine materials such as high temperature alloys, titanium alloys, cobalt-based alloys, and nickel-based alloys such as Inconel 718. Waukesha, Wisconsin-based Walter has a solution for this range of applications – high power impulse magnetron sputtering (HIPIMS) physical vapor deposition (PVD) coating for cutting tools. In contrast to conventional PVD processes, HIPIMS subjects the target to short pulses of a few kilowatts of power, producing extremely smooth surfaces, lower friction and edge build-up, and excellent bonding of layers to the substrate and layer thicknesses distribution.

Hard, very tough materials that are becoming popular (such as Inconel 718DA with 42HRC in the aerospace industry or Ti-6Al-4V in the medical industry) have complex requirements for indexable inserts. Tough materials have a high tendency for adhesion, especially when they have a high nickel content, causing chips to stick to the cutting edge and form a build-up. Dimensional stability and surface quality suffer in that environment. Accelerated wear on cutting edges had to be accepted until now, especially in the case of high-strength materials.

During turning operations with high to medium depths of cut, chemical vapor deposition (CVD)-coated indexable inserts offer good-to-outstanding possibilities. However, they reach their limits in machining applications such as finishing and fine finishing, particularly where precision and tool life are concerned.

Innovation, potential

Gerd Kussmaul, senior turning product manager at Walter, describes the concept behind the new HIPIMS PVD-coated indexable inserts.

“Even if the fine finishing and finishing of ISO M, S, P, and N materials with the highest requirements for surface quality are still special or niche applications, we see great potential due to dynamic growth in the market right now,” Kussmaul says.

Fine finishing involves turning operations which are designed to achieve a consistently good surface quality.

“Walter has been looking for geometries and cutting tool materials that achieve this with process reliability,” Kussmaul explains. “The new PVD HIPIMS coatings demonstrate ideal properties for achieving extremely smooth surface and great layer adhesion on sharp cutting edges.”

Indexable inserts with extremely sharp geometries, such as the FN2 or the MN2, benefit from this coating process because extremely stable cutting edges are produced. Even under high loads, the layers do not chip off and the cutting edges do not break away. In addition, the high level of edge stability ensures lower levels of more-even wear. Even wearing ensures dimensional stability and surface quality throughout the tool’s life.

Extremely smooth, HIPIMS coatings can machine sticky aluminum alloys and other materials which would otherwise stick to the cutting edge during machining. Typical forms of wear such as built-up edges or significant flank face wear caused by chemical and physical reactions with adhering workpiece rarely occur.

Increased machining volumes

As Kussmaul notes, people don’t necessarily change from a tried-and-true cutting tool material without good reasons.

“Among other factors, the outstanding results achieved by the new HIPIMS grades regarding tool life and surface quality speak in their favor. This is clear from comparative tests,” Kussmaul says.

When performing finishing operations on tool steel H13 with 54 HRC, it was possible to increase the tool life by 275%. And the surface value of Ra 0.8µm was achieved throughout the entire tool life with process reliability.

Kussmaul describes another application: finishing Inconel 718DA at a cutting speed of 262fpm, with the new grade WSM01 and achieving a cutting time and tool life of 18 minutes – double the previous WXN10 grade.

Process reliability up, cost down

Walter's HIPIMS PVD indexable inserts can be applied anywhere that maximum precision, surface quality, and process reliability are required, particularly when dealing with difficult-to-machine materials. Inserts lower costs because the HIPIMS PVD coating, in conjunction with a carbide substrate, results in a cutting tool material with consistently high machining quality and long tool life. This is especially true for difficult machining such as fine finishing and for sticky materials such as aluminum alloys with high silicon content. Tool life and surface quality gains compared to previous indexable inserts are dramatic, often leading to significant cost reductions.

Walter USA LLC
https://www.walter-tools.com

In aircraft maintenance and repair, eddy current devices have long been used to non-destructively test wheels, struts, propellers, airframes, hubs, engine components, and other parts for flaws such as cracks, fatigue, or corrosion in aluminum and steel alloys.

Traditionally, manufacturers used multiple eddy current test instruments to address the full scope of work – inspecting surfaces, welds, tubing, and bolt holes.

“When it comes to metal fatigue testing, there are several different ways to test the materials,” says Beau Klingbeil, general manager of Eclipse Aerospace Inc.’s Chicago service center, which services the manufacturer’s twin-engine, single-pilot jet line. “Eddy current is the least expensive, least invasive way of doing those tests, so we typically end up using it on a weekly basis.”

Meter-type instruments are often limited to aluminum airframe inspection with a set frequency and probe type, but more sophisticated impedance-plane units can be set to various frequencies for more applications. However, these tools can be complicated to use, even for those with some training.

Fortunately, for busy airframe and powerplant (A&P) mechanics who do not specialize in non-destructive testing (NDT) yet are responsible for broad repairs, streamlined testing using sophisticated impedance-plane devices is possible. These devices provide accurate test results and dramatically simplify operation while using various probe types.

Simplifying lift-off, operation

All-digital eddy current instruments that use incremental push-button adjustment, instead of rotating knobs, are common in aviation repair. However, operating the devices can be so complex that mechanics unfamiliar with their peculiarities must refer to the manual for setup and use.

This is particularly true when it comes to lift-off, which is required at the start of eddy current testing to offset any surface abnormalities or hand movement that could distort measurement accuracy. During lift-off with such instruments, mechanics typically end up pressing buttons and waiting for the computer processor to rotate through the slow setup process.

“With most digital eddy current units, you push buttons to incrementally set a variety of different parameters,” says Klingbeil, an A&P mechanic and Level 2-certified in eddy current testing. “You have to constantly go back and forth to adjust single amplitude, phase angle, and vertical/horizontal position.”

Klingbeil found a better alternative by turning to an impedance-plane eddy current instrument by Centurion NDT, a Streamwood, Illinois-based manufacturer of portable eddy current and ultrasonic equipment.

“I can step up for an eddy current test in minutes and be ready to go with the NDT-1100,” Klingbeil says. “The portable unit is very easy to use and performs a variety of tests.”

The instrument, about the size of an iPad, will locate surface and near-surface defects and conductivity changes in magnetic and non-magnetic materials, and can cover about 85% of the applications that eddy current testing might perform – crack detection; sorting materials according to hardness alloy, carbon content, tensile strength, and grain structure; and measuring coating and sheet thickness, and the relative conductivity of critical materials.

Unlike traditional all-digital units, the instrument has an automatic balance/null feature that reduces setup time for manual operation. By moving the probe and turning a phase control knob on the front panel, lift-off can be completed in seconds.

According to Klingbeil, the unit eliminates common adjustment errors that otherwise occur at lift-off and during operation.

“Unlike traditional all-digital units, the instrument has an automatic balance/null feature that reduces setup time for manual operation.”

“You just enter the frequency with a push button, and then turn knobs to fine tune everything else,” he says. “I don’t deal with a lot of false indications. It eliminates most of those.”

Regarding ease of use, he adds, “When you’re adjusting things such as the single amplitude, the phase angle, and the vertical and horizontal position, you don’t use a push button that functions incrementally. Instead, you can fine tune it exceptionally well and accurately with knobs.”

Mechanics must test everything from the airframe to the wheels, so it is important to select an eddy current instrument that accommodates an array of probe and coil types.

Klingbeil stocks six probes from Centurion NDT. Digital frequency selection, probe drive, and impedance adjustments allow the operator to optimize system performance for whichever probes or coils are selected. Eclipse’s Chicago service center uses two pencil-probe testers with different frequencies, two probes for wheel-specific testing, and two bolt-hole probes to test different wheel types.

“The pencil probe testers have different angles because some areas we have to NDT are hard to reach,” Klingbeil says. “One pencil probe tester is straight, one is angled 90° to improve reach.”

Among the most specialized probes are those that detect heat damage along the wheel bead seat, the critical area where the rubber edge of a tire contacts the wheel. To accommodate various wheels, Centurion NDT offers several wheel bead-seat probes.

To improve accuracy and ease eddy current testing of the wheel bead seat, the company also offers a wheel turntable accessory. Instead of manually running the probe around the wheel, which can lead to less reliable test results, the motorized turntable provides a constant rotational speed, specific to the wheel diameter. Greater consistency than can be achieved manually makes even the smallest cracks more visible on the screen.

“I’m an airframe and power plant mechanic, so NDT is not my primary job; it’s something I’ve certified along the way,” Klingbeil says. “If you’re a novice learning how to do NDT, it’s a good unit because of the simplicity and accuracy. You could use it at a service center platform or in the field for mobile response. This will do everything that other units will but is a lot faster and more portable.”

Centurion NDT
https://www.centurionndt.com

At the beginning of 2019, the U.S. government was in partial shut-down, interest rates were rising, stock markets were highly volatile, and a majority of business leaders surveyed by the Associated Press expect a recession this year. But you didn’t hear such doom-and-gloom from the aerospace community. In the final weeks of last year, Airbus, Boeing, and Embraer confirmed orders for more than 400 jetliners. And, despite engine shortages and other supply-chain challenges, Airbus and Boeing delivered record numbers of aircraft – and each has seven or more years of production to work off a 13,450 airplane backlog.

Airbus is building a new final assembly line
in Mobile, Alabama to produce A220s for U.S.
customers. Photo credit: Airbus SES

All those orders translate to jobs. Airbus is seeking about 600 experienced aircraft structure/installation mechanics, aircraft cabin installers, and aircraft electricians to work on the assembly line it’s building in Mobile, Alabama, to produce A220 regional jets – formerly known as the Bombardier CSeries. A recent Washington state aerospace job fair drew more than 1,500 prospective candidates to meet with nearly 40 companies looking to hire. Plans to continue ramping up build rates will require more production efficiency from suppliers.

Airbus delivered 800 aircraft in 2018 (20 of those were A220s via Bombardier) with 747 net orders. (See commercial aircraft production table for comparison.)

Airbus is producing A320 family single-aisle jetliners at the rate of 52 per month, with plans to go to 60 or more. 

Embraer’s delivery summary for 2018 was not available at press time, but at the end of Q3 2018, the company had delivered 112 aircraft: 57 E-jet commercial airliners of all types and 55 executive jets (40 light, 15 large). Its commercial jetliner firm-order backlog stood at 251, valued at $13.6 billion, on Sept. 30, 2018. Embraer officials still expect 85 to 95 commercial jet deliveries for the year but have revised down the estimate for executive jets to 91 from 105 to 125, citing the global market for executive jets is recovering more slowly than expected.

For 2019, company officials forecast deliveries of 85 to 95 commercial jets, 90 to 110 executive jets (light and large), 10 A-29 Super Tucano military trainer aircraft, and two multi-mission KC-390 cargo aircraft. With corporate and government approvals in hand, officials expect its 20/80 commercial join venture with Boeing to close by year’s end. 

In 2018, Bombardier gave control of its CSeries (now A220) regional jet to Airbus, sold its Dash 8 Q Series turboprop aircraft program to Longview Aviation Capital Corp., and sold its business aircraft’s flight and technical training activities to CAE. The transportation company is focusing aviation efforts on its CRJ regional jets; Challenger, Global, and Learjet business aircraft brands; and aerostructures and engineering services. Data on 2018 deliveries and orders were not available at press time.