Elemental Analysis of Metal Parts and Powders Produced by Additive Manufacturing

Table of Contents

Introduction
Quality Control Process
Elements Which Have an Influence on the Material Properties
     Steel
     Titanium
Analysis Methods
     O/N/H Analysis
     C/S Analysis
Conclusion

Introduction

An essential part of industrial product development is the manufacture of prototypes and initial samples, irrespective of whether the product is the complex part of an airplane or a simple screw. To fabricate single pieces, which are frequently rather small, in a production environment is generally a costly procedure. A special application field of powder metallurgy called additive manufacturing has developed in the past few years based on this cost-benefit calculation.

Additive manufacturing (AM) refers to the “process of joining materials in order to make objects from 3D model data.”1 AM generates objects layer upon layer from varied metal alloy powders or metal powders. The specifications of the manufacturing process are based on the possibilities and requirements of the user, and on the size and type of the object to be produced.

In recent years, several different methods have been established in the industry, such as:

Table 1. Additive manufacturing methods1.

Most AM methods are based on the same procedure. A laser beam locally melts the upper powder layer which solidifies and produces a layer of solid material. This is repeated layer by layer until the final object is produced. The quality of the unused powder is established by particle size analysis (sieving), and in certain cases also by elemental analysis, before it is returned to the manufacturing process.

Figure 1. Additive manufacturing by Laser Metal Deposition.1

Quality Control Process

Additive manufacturing is currently becoming a well-established production technology. However, as it is still new, the desired process steps have not been uniformly defined yet. There are, for instance, no industry-wide standards describing the quality control process. The particle size distribution of the powder used for AM is an established parameter. However, particle size should not be the only characteristic employed for quality control.2

Additive manufacturing is currently becoming a well-established production technology. However, as it is still new, the desired process steps have not been uniformly defined yet. There are, for instance, no industry-wide standards describing the quality control process. The particle size distribution of the powder used for AM is an established parameter. However, particle size should not be the only characteristic employed for quality control.2

Elements Which Have an Influence on the Material Properties

Steel

There are a number of elements which influence the properties of steel with carbon at the top of the list. Steel is classified into different quality grades and application fields, based on the type and concentration of these alloy elements (C, Si, P, S, Mn, Cr etc.). In the following the extremely vital non-metallic elements and their effects are described.

Carbon [C]: The carbon content affects different physical parameters of steel. This ferrous alloy comprises of carbon ranging between 0.0002% and 2.06%. An increase in the carbon content leads to a lower melting point. Furthermore, hardness and brittleness increase with the carbon content.

Figure 2. Iron-carbon phase diagram.

Sulfur [S]: If the alloy comprises of sulfur, this increases the machinability of the steel, i.e. the material’s suitability for being treated by methods like milling or drilling. The higher the sulfur content, the lower the ductility.

Nitrogen [N]: The nitrogen content can be divided into undesired and desired content. There are some exceptional applications which allow a high nitrogen concentration. In these cases its chemical form has to be considered. Nitrogen in its elemental form is localized along the grain boundaries and influences the ductility of steel in a major way. The nitrogen content which is bound to other elements is generally not considered important.

Oxygen [O]: Oxygen is a so-called steel parasite since it makes the steel brittle and causes ageing brittleness.

Hydrogen [H]: Hydrogen in steel causes degrading of the mechanical stability. Hydrogen embrittlement is extensively feared as it may cause substantial economic and technical damages. It means that the protons fasten themselves to the metal matrix which could develop cracks in the steel.

Titanium

Hydrogen [H]: Has the same effect on titanium as on steel. Hydrogen may impact the formation of mixed phases in titanium alloys.

Nitrogen [N]: Nitrogen increases the brittleness of titanium.

Oxygen [O]: Even minimum amounts of oxygen have a significant effect on the hardness or toughness of titanium. The Specification Book shows that even small differences in the oxygen content may be able to determine the difference between low-quality titanium (grade 3: 0.35%) and high-quality (grade 1: 0.18% O). Oxygen changes the physical and mechanical properties of titanium significantly. Titanium with an oxygen concentration of 0.1% is approximately three times more stable than with a concentration of 0.3%.

Sulfur [S]/Carbon [C]: These elements only have a very slight effect on titanium.

The determination of the described element concentrations should be performed before and after the additive manufacturing process in order to guarantee that both the raw materials and the final product possess the desired quality.

Analysis Methods

There are different ways of measuring element concentrations and impurities, most of which require destruction of the sample. This is done to guarantee that all relevant components of the analyzed sample are properly released.

Combustion analysis provides a number of benefits. It is possible to measure the samples in solid form, meaning direct measurement without previous treatment. The average particle size needed for metal powders used for additive manufacturing processes lies between 5 µm and 150 µm. This is determined by particle size analysis, for example by Dynamic Image Analysis. If the powder has the right size distribution it can be examined for elemental concentrations by combustion analysis.

The measurement of H/C/N/O/S cannot be performed in one single analysis. Nitrogen, oxygen and hydrogen are analyzed in one step and carbon and sulfur in another.

This is due to different methods being applied:

O/N/H Analysis

The sample is dropped into a graphite crucible and melts because of the high temperature. Consequently, nitrogen, oxygen and hydrogen are released. Oxygen transforms to CO on the surface of the hot crucible. The gases from the crucible are removed by the inert carrier gas.

A copper oxide catalyst transforms CO to CO2 which is detected in the infrared cells. An infrared ray with a particular wave length is used for exciting the carbon dioxide molecules. The loss of energy, which was transferred to kinetic energy, is used for determining the exact oxygen concentration of the sample. The hydrogen and nitrogen content are measured in a thermal conductivity cell.

Figure 3. Infrared cell.

The ELEMENTRAC thermal conductivity cell is based on a micromechanical silicon chip which is attached to a membrane and operates independently of a reference gas flow. If the thermal conductivity of the gas changes, for example if nitrogen is discharged from the sample, the heating capacity needed for heating the membrane also changes. This is specified by a measuring signal. The method is sensitive and robust, and it ensures stable measuring results over a wide concentration range.

Figure 4. Thermal conductivity cell.

Table 2. Different thermal conductivities.

[1] CRC Handbook of Chemistry and Physics, 1995-1996, 76th Edition

Table 3 shows typical results for a simultaneous oxygen and nitrogen analysis of a steel sample. Reproducibility is clearly below 1 ppm, even for very low concentrations.

Table 3. Measurement of Eltra 91100-1001 #714A.

C/S Analysis

In the induction furnace, the sample is melted in a pure oxygen atmosphere, causing sulfur to react to sulfur dioxide (SO2) and carbon to react to a mixture of carbon dioxide (CO2) and carbon monoxide (CO).

The combustion gases pass through a dust filter and moisture absorber for purification. In the next step, the sulfur dioxide is identified in infrared cells. In ELTRA’s CS-800, it is possible to adapt infrared cells with different sensitivities (high/low) according to the user’s requirements. Oxidation of both, carbon monoxide to carbon dioxide and sulfur dioxide to sulfur trioxide follow the sulfur measurement. The SO3 gas is removed with cellulose wool; the carbon content is identified by infrared cells which allow for individual customization. ELTRA analyzers can be equipped with up to four independent infrared cells.

Figure 5. Carbon/sulfur analysis procedure.

The sample is weighed in a crucible and then covered with tungsten for analysis. Table 4 displays a typical result for a steel sample.

Table 4. Measurement of AR 875 #51256.

Conclusion

Non-metallic elements such as hydrogen, carbon, oxygen, sulfur and nitrogen influence the physical properties of metallic materials. These elements may be found in the powdered raw materials employed for additive manufacturing, or they could also be introduced during the production process. Thus, detailed quality control should always focus on analysis of the raw material and the final product. Combustion analysis provides reliable and convenient solutions to reproducibly measure element concentrations in a range from a few ppm to percentages.

References

1 Introduction to additive manufacturing technology, www.epma.com/am

2 Berumen, S.; Bechmann, F.; et al, Quality Control of laser and powder bed-based Additive Manufacturing (AM) technologies, Physics procedia, 5, 617-622, LANE 2010

This information has been sourced, reviewed and adapted from materials provided by ELTRA GmbH.

For more information on this source, please visit ELTRA GmbH.

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New York, LA seen by Delta as bases for new Bombardier jet

By Michael Sasso and Frederic Tomesco / Bloomberg News

Delta Air Lines is eyeing New York and Los Angeles as the main bases for Bombardier’s new jetliner next year, offering a glimpse of how carriers can add service economically with the not-quite-midsize plane.

Dallas is also likely to get a lot of C Series flights, Delta said in an internal memo to pilots, a copy of which was reviewed by Bloomberg News. That sets up a test of the carrier’s ability to use the single-aisle aircraft to attract customers in the backyard of American Airlines Group and Southwest Airlines.

Delta is the first major U.S. carrier to buy the C Series, a midrange aircraft that offers roomier interiors than regional jets while typically carrying fewer passengers than a Boeing 737 or Airbus A320. The Bombardier aircraft, which the Montreal-based company has spent at least $6 billion to develop, should enable airlines to offer comfy rides to midsize cities without flooding the market with too many seats.

“From the standpoint of operating costs, from the standpoint of ownership costs, it’s an ideal aircraft for these not-quite-mainline markets,” said Robert Mann, an aviation consultant and former airline executive. “If it performs as advertised, reliably, it’s going to be a real game-changer.”

Morgan Durrant, a spokesman for Delta, declined to comment on the memo or how the company will use the C Series. The aircraft is scheduled to enter service for the Atlanta-based airline in the second quarter of 2018, according to the Aug. 7 notice to pilots, which described preliminary plans for the planes.

The U.S. airline ordered at least 75 of the CS100 models last year in a deal valued at $5.6 billion, before the discounts that are customary for large aircraft purchases. Ordering the C Series was a bit of an anomaly for Delta under former Chief Executive Officer Richard Anderson, who had historically preferred more tested airplanes over new models. He handed over the reins as CEO to Ed Bastian days after the order was announced.

The purchase threw a lifeline to Bombardier after the C Series program came in two and a half years late and more than $2 billion over budget. But the transaction also prompted Boeing to file a trade complaint with the U.S. government, accusing Bombardier of selling Delta the planes at “absurdly low” prices while benefiting from unfair Canadian government subsidies and calling for tariffs. Bombardier has denied the allegations.

Air Baltic Corp., which began flying CS300 planes in December, has seen a 21 percent improvement in fuel economy compared with the Boeing 737-300s that the model is replacing, Chief Executive Officer Martin Gauss has said. Bombardier had promised a 19 percent boost. Passenger feedback has focused on lower noise levels, a brighter interior and bigger spaces for stowing baggage, Gauss added.

Deutsche Lufthansa AG’s Swiss unit, which last year became the first operator of the CS100, has also praised the jet’s performance.

Delta will place the new CS100 planes on popular routes now served by the airline’s largest 76-seat regional jets, which will free up those planes to replace 50-seat aircraft around Delta’s system, President Glen Hauenstein said last month. He said New York would get the first CS100, without providing additional details. The plane has 108 seats in a standard dual-class configuration, according to Bombardier.

In Dallas, Delta may see a chance to poach some business customers from hometown carriers American and Southwest, potentially taking a bite out of their profit margins, said aviation consultant George Hamlin.

“Southwest is very much a thorn in Delta’s side in its home market in Atlanta,” Hamlin said. “The airline business is about margins, so if you can pry a modest amount of business from your competitor, the margin in that market may become problematic for the incumbent.”

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Great Barrington: Annual Bike-N-Fly festival slated Aug. 19

Great Barrington Rotary and Airport will present the seventh annual Berkshire Bike-N-Fly Festival from 9 a.m. to 4 p.m. Saturday, Aug. 19, at the Great Barrington Airport, 70 Egremont Plain Road.

Bike rides of varying lengths through the Berkshires begin at 9 a.m. Pre-registration for the bike ride is required.

A full day of activities features scenic airplane, bi-plane, helicopter, and balloon rides; paragliding and parachute jumping demonstrations; model planes, a flight simulator, new and old airplanes, food and other vendors, live music, face painting, bouncy castle, raffle prizes, a dunk tank, and more.

New attractions include a Cow Plop game and a mountain bike demonstration featuring world record holder Jeff Lenowsky.

Admission is $15 per car load. Proceeds from the event help fund scholarships and community projects.

For more information, visit www.berkshirebikenfly.org.

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Model airplane group’s fundraiser takes off Saturday at Southwest Area Park

The Southwest Area Park Modelers, expanding its annual community-service fundraiser, will hold its first Baltimore Bash Saturday.

The Baltimore Highlands-based group is part of the Academy of Model Aeronautics, a nonprofit that promotes model aviation as a recreational sport and hobby.

The group, which has about 120 members, has held a benefit for a veteran-related charity the last three years. This year, the gathering will benefit Disabled American Veterans, a nonprofit that assists disabled veterans in need and their families.

Art Vail, the group’s treasurer and event coordinator, said there are several veterans who are part of it.

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Charles Kramer

Our much-loved father, grandfather, and friend, Charles Kramer, 88, of Willard, Missouri, died Monday, Aug. 7, 2017, after living with Parkinsons Disease for many years.

Charles Thomas Kramer was born on April 13, 1929 to Louis and Mabel (Miller) Kramer in Le Mars. He graduated from Le Mars Central High School in 1947.

Charles was drafted into the Marines and served two years during the Korean War where he was stationed in Hawaii making a trip to Korea to retrieve wounded soldiers. Most notably, during his tour of duty he was witness to atomic bomb testing in Nevada.

On June 29, 1955, he was united in marriage to Lillian Elsie Graff at St. Pauls Evangelical United Brethren Church in Jamestown, North Dakota. They raised their seven children in Le Mars.

Charles was a contractor his entire life: first working at Kramer Construction alongside his own father and brother in Le Mars, and later with his sons, Bob, Jim and Rich Kramer where he retired from Rich Kramer Construction, Springfield, Missouri in 2005.

Had it not been for Parkinsons he would probably have never retired.

As a youngster, Charles enjoyed building model airplanes. He had so many hanging from his bedroom ceiling his father was afraid to enter for fear of disturbing them. He also was an avid woodworker, passing both of these passions on to his sons. Charles also enjoyed trains. As an adult he acquired his own miniature engine and cars that his grandchildren could actually ride on. Many Saturdays were spent riding on grandpas train.

Charles tough Marine exterior hid his loving heart for his wife, children and grandchildren, always meeting their needs. He had a quiet faith about him, always doing for others who were less fortunate.

Charles was a member of New Life Baptist Church of Willard, Missouri and a former member of First Baptist Church of Le Mars.

Left to celebrate Charles life are his sons, Dean Kramer of Willard, Missouri; Robert (Sheila) Kramer, Willard, Missouri and children David, Sarah, Daniel, and Michaela; James (Dawn) Kramer of Willard, Missouri and children Roxana, Rochelle, and Roslyn; Richard (Agnieszka) Kramer of Rogersville, Missouri and children Nick (Nickie), Michael, Ayron (Carlos), Michael (Annie), and Mark; and daughters, Joan (Tom) Loew, Oelwein, and children Jake and Jenna; and Marie (Dean) Plueger of Suwanee, Georgia and children Arabella and Eliana; six great-grandchildren; many nieces and nephews; and a sister, Marjorie Kramer of Le Mars.

He was preceded in death by his beloved wife of 61 years, Lillian on Easter of 2017, his parents; his daughter, Ann; his daughter-in-law, Debra Kramer; his brother and his wife, Forrest and Joyce Kramer; his brother-in-law and his wife Rev. David and Laura Graff; and his sister-in-law and her husband, Helen and Robert Crites.

Willard, Missouri visitation will be held at New Life Baptist Church in Willard from 4-6 p.m., Thursday, Aug 10, with a service at 6 p.m.

Le Mars visitation services will be from 9-10:30 a.m., Saturday Aug. 12, at First Baptist Church in Le Mars. The funeral service, with military honors, will be at 11 a.m., with a luncheon to follow.

Arrangements under the direction of Wilson-Griffin Funeral Home, Ash Grove, Missouri.

Memorials may be directed to the Michael J. Fox Foundation for Parkinsons Research, New Life Baptist Church, Willard or First Baptist Church, Le Mars.

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Aftermath: High, Heavy and Slow

In June 2010, a Cessna T310R crashed in fine weather while on final approach at Ruidoso, New Mexico. Five people perished, two survived. The survivors were 12 and 16 years old, and I suspect that they were probably in the aftmost seats. Another young person, an 11-year-old boy, was double-­belted in the right front seat with his mother.

Parenthetically, FAR 91.107, which concerns seat belts, does not explicitly forbid the practice of double-­belting. The rule says everyone (except children under 2) must occupy a seat with safety belts, but does not stipulate that all passengers be in different seats. After this accident, the National Transportation Safety Board urged the FAA to amend the rule, but the FAA chose not to do so.

The 310 is intended to carry only six people, including the pilot, but despite the overpopulation the NTSB concluded that the airplane’s weight and CG location were within limits and loading was not the cause of the accident. The cause was, instead, a familiar and banal one: The pilot got too slow, and the airplane stalled and departed into an incipient spin. “Contributing to the accident,” the NTSB went on, “was the pilot’s limited experience in the airplane make and model.”

I would suggest, however, that the loading probably did have something to do with it.

The private pilot, 49, had around 850 hours. In an insurance document associated with his acquisition of the 310 three months before the accident, he reported 156 hours of multiengine time, including five hours in Cessna 310s. The pilot’s insurance policy required that he receive five hours of dual instruction in the 310 (three of them instrument dual, although he did not have an instrument rating) before he would be covered to fly solo. Two months before the accident, he logged 3.1 hours of instruction in the accident airplane; no record of subsequent flights was found.

That the pilot did not feel entirely familiar with the airplane is suggested by the fact that he and one passenger took off from the 3,600-foot runway of their hometown — in flat country, near sea level — and flew 20 miles to another airport with a 5,700-foot runway to emplane the other five. If this was a precaution, it was a superfluous one; even at gross weight, the T310R clears a 50-foot obstacle in less than 1,700 feet from brake release.

The density altitude at Ruidoso was 9,500 feet when the 310 arrived. The pilot radioed on the common traffic advisory frequency to report 30 miles out, then 10 miles, and said that he intended to land on Runway 24. The wind at the time was 050 at 5 knots, so he would be landing with a slight tailwind.

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New York, LA Seen by Delta as Bases for Newest Bombardier Jet

Delta Air Lines Inc. is eyeing New York and Los Angeles as the main bases for Bombardier Inc.’s new jetliner next year, offering a glimpse of how carriers can add service economically with the midsize plane.

Dallas is also likely to get a lot of C Series flights, Delta said in an internal memo to pilots, a copy of which was reviewed by Bloomberg News. That sets up a test of the carrier’s ability to use the single-aisle aircraft to attract customers in the backyard of American Airlines Group Inc. and Southwest Airlines Co. 

Delta is the first major U.S. carrier to buy the C Series, a midrange aircraft that offers roomier interiors than regional jets while typically carrying fewer passengers than a plane from the Boeing Co. 737 or Airbus SE A320 families. The Bombardier aircraft, which the Montreal-based company has spent at least $6 billion to develop, should enable airlines to offer comfy rides to midsize cities without flooding the market with too many seats.

“From the standpoint of operating costs, from the standpoint of ownership costs, it’s an ideal aircraft for these not-quite-mainline markets,” said Robert Mann, an aviation consultant and former airline executive. “If it performs as advertised, reliably, it’s going to be a real game-changer.”

Morgan Durrant, a spokesman for Delta, declined to comment on the memo or how the company will use the C Series. The aircraft is scheduled to enter service for the Atlanta-based airline in the second quarter of 2018, according to the Aug. 7 notice to pilots, which described preliminary plans for the planes.

Delta climbed 1.3 percent to $50.13 at 12:36 p.m. in New York. Bombardier advanced 2 percent to C$2.61.

Boeing Complaint

The U.S. airline ordered at least 75 of the CS100 models last year in a deal valued at $5.6 billion, before the discounts that are customary for large aircraft purchases. Ordering the C Series was a bit of an anomaly for Delta under former Chief Executive Officer Richard Anderson, who had historically preferred more tested airplanes over new models. He handed over the reins as CEO to Ed Bastian days after the order was announced.

The purchase threw a lifeline to Bombardier after the C Series program came in two and a half years late and more than $2 billion over budget. But the transaction also prompted Boeing to file a trade complaint with the U.S. government, accusing Bombardier of selling Delta the planes at “absurdly low” prices while benefiting from unfair Canadian government subsidies and calling for tariffs. Bombardier has denied the allegations.

Air Baltic Corp., which began flying CS300 planes in December, has seen a 21 percent improvement in fuel economy compared with the Boeing 737-300s that the model is replacing, Chief Executive Officer Martin Gauss has said. Bombardier had promised a 19 percent boost. Passenger feedback has focused on lower noise levels, a brighter interior and bigger spaces for stowing baggage, Gauss added.

Deutsche Lufthansa AG’s Swiss unit, which last year became the first operator of the CS100, has also praised the jet’s performance.

Regional-Jet Replacement

Delta will place the new CS100 planes on popular routes now served by the airline’s largest 76-seat regional jets, which will free up those planes to replace 50-seat aircraft around Delta’s system, President Glen Hauenstein said last month. He said New York would get the first CS100, without providing additional details. The plane has 108 seats in a standard dual-class configuration, according to Bombardier.

In Dallas, Delta may see a chance to poach some business customers from hometown carriers American and Southwest, potentially taking a bite out of their profit margins, said aviation consultant George Hamlin.

“Southwest is very much a thorn in Delta’s side in its home market in Atlanta,” Hamlin said. “The airline business is about margins, so if you can pry a modest amount of business from your competitor, the margin in that market may become problematic for the incumbent.”

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