What Could Make Cold Spray Additive Manufacturing (CSAM) Better? – UAM Post Processing

By Sarah Jordan

Cold spray additive manufacturing (CSAM) is a new process.  It is based on traditional cold spray technology.  The process works by accelerating powder particles to nearly the speed of sound.  This gives the particles the needed energy to bond to a material.

CSAM has been adopted for use in repair.  It is also used for component manufacturing.  It is a solid-state process.  This means that no melting occurs.  Typically, the temperature is below 400℉.  CSAM has been shown to work with most metals and alloys.  It also can work with metallic glasses, metal matrix composites (MMCs), and even polymers. The process has several benefits including:

  • High deposition rate of up to 100 lbs. per hour. 
  • There are larger build envelopes due to not needing an inert gas or vacuum.  This means larger parts can be made.
  • Low energy use.
  • Parts do not have heat affected zones.  They do not require a post process heat treatment.  This saves time, prevents distortion, and makes repairs easier.
  • The process can join different metals to make new metal matrix composites.

With such beneficial capabilities, CSAM is utilized in many industries.  These include aerospace, defense, tooling applications, and more. 

A problem with CSAM has been that the material can fall short of the expected properties.  This is particularly true for harder metals which tend to have more porosity and less bonding. Attempts have been made to address this with post-processing.  Current techniques, however, can cause cracks, distortion, and thermal-induced metallurgy problems.  The application of heat is an issue for any CSAM that involves multiple metals.  When heat is applied the two metals can diffuse into one another, creating undesirable brittle intermetallics. 

Ultrasonic additive manufacturing (UAM) has recently been utilized as an alternative post-process technique.  Normally UAM is used to consolidate metal foils into a solid piece of metal.  The process uses high-powered ultrasonic vibrations (20,000 to 30,000 Hertz) in combination with downward pressure.  This creates a friction bond that joins the foils together. 

In the case of UAM as a post process, the metal foils were removed.  The UAM head was used on the CSAM surface to further consolidate the cold spray material.  The benefits of UAM as a post process are that it has similar characteristics to CSAM.  UAM is also fast, has large build envelopes, does not require an inert gas or vacuum, has low energy use, and is a solid-state process.

In the study, cold spray was used to produce MMCs made of two blends of metal powders.  The powders used were Cu-38Ni and CrC-30NiCr.  Then UAM was performed on cold spray deposits to further consolidate the material.  Testing included hardness, adhesive strength, tensile properties, porosity, and resulting microstructure.

The application of the UAM post-process showed great results:

  • The ability to compress and level the surface coating and improve the surface finish.
  • Hardness showed a slight increase of 2-5%.
  • Adhesive strength increased 8-13%. 
  • Yield strength increased 4-11%.   
  • The grain size was also shown as being refined which can potentially improve the corrosion resistance. 

This is an initial study to use UAM as a post process.  The results appear very promising!

My Experience as a 3D Printing Intern

By Guest Blogger Matthew Burkhart October 2021

My name is Matthew Burkhart, and I spent the summer of 2021 working as an engineering intern for Fabrisonic. I am currently a senior at The Ohio State University pursuing a bachelor’s degree in Aerospace Engineering.

Prior to applying to Fabrisonic, I had little knowledge of additive manufacturing. I applied to Fabrisonic in January of 2020 for a part-time student machine operator position. This was a step outside of my comfort zone as I had never operated a CNC mill.  The minimal 3D printing experience I had was from high school.

After getting hired, I was introduced to Fabrisonic’s ultrasonic additive manufacturing (UAM) technology, and it immediately drew my curiosity. I began working on Fabrisonic’s SonicLayer 4000 producing early-stage production parts that involved welding aluminum sheets onto parts with various geometries. This was a great opportunity to expand my knowledge of UAM. I also worked with our great team of engineers and technicians to help develop my intuition into the additive manufacturing process.

Figure 1 Fabrisonic SonicLayer 4000

My experience as a part-time operator opened the door for me to become an engineering intern for Fabrisonic. As an engineering intern for Fabrisonic, I was immediately given a good amount of responsibility. I was tasked with building a SonicLayer 1200 machine. The SonicLayer 1200 is based on a Tormach 1100 MX CNC mill that is retrofitted with Fabrisonic’s UAM assembly. It is Fabrisonic’s smallest machine with its 10 x10 x 10-inch build volume. The SonicLayer 1200 is a very user-friendly machine and is a less expensive option for UAM capabilities.

Working on the SonicLayer 1200 has been a great experience for me to develop my skill set as an engineer. The responsibility that I was given on this project as an intern has been my favorite part of working with Fabrisonic. At larger companies, it is rare that an intern would be given this amount of responsibility. The startup environment of Fabrisonic gave me the opportunity to develop hands-on experience and play a part in the development of several projects.

My work has involved placing work orders with machine shops, developing electrical circuits, routing pneumatic lines, constructing the UAM components such as the weld head assembly below.  I also aided in the final assembly of the machine. I followed the lead of our production engineer Dan King, but I was expected to contribute a large role in the overall development of the machine.

Figure 2 Fabrisonic UAM weld head assembly

We recently finished the assembly of this machine and running test programs to certify its completion. It has been a great experience working on this project from its start and seeing the final product in operation. The machine recently shipped to its new home. 

Figure 3 Fabrisonic prepares to ship a SonicLayer 1200 machine

Now that my senior year has started, I look to apply my newfound knowledge about additive manufacturing to the senior design project. The introduction to additive manufacturing has helped me find my path within the vast aerospace field. I believe the application of UAM in the aerospace field will continue to grow and I want to be a part of this growth.

There are currently many design challenges facing the aerospace industry that I believe UAM can help solve. One of these challenges is heat dissipation. This is especially true for hypersonic flight conditions where temperatures can reach upwards of 2000 °C. With current subtractive manufacturing techniques, it is very difficult to create complex geometries within the structure of an aircraft. Using additive manufacturing techniques, it is possible to develop much more effective cooling channels that could be utilized within hypersonic aircraft such as with the heat exchanger examples below.

Figure 4 3D metal printed heat exchangers from Fabrisonic

My internship at Fabrisonic has been a very rewarding experience. It has helped me develop a background in additive manufacturing and given me the opportunity to expand my skillset. The future of additive manufacturing is very promising, and I am very grateful for the opportunity I was given to work with Fabrisonic’s great team of engineers and technicians.