Microvoids are holes inside the object which act as internal 'cracks'. Definitely a big concern which is why I've had a brief look into their original patent here:
https://patentscope.wipo.int/search/en/detail.jsf?docId=WO2013149291&tab=PCTDESCRIPTIONThe relevant part is this:
"The average size of the titanium particles that are cold sprayed is likely to influence the density of the resultant deposition on the support member. Preferably the deposition is dense and free from defects, connected micro-voids (leakage) and the like, since the presence of such can be detrimental to quality. Typically, the size of the particles applied by cold spraying is from 5 to 40 microns with an average particle size of about 25 microns. One skilled in the art will be able to determine the optimum particle size or particle size distribution to use based on the morphology of the powder and characteristics of the structure that is to be formed."
My (conservative) guess is that to get the results they announced, they used very high-quality titanium powder that has a very small range variance, i.e. 20-25 microns. The probable supplier is AP&C, as their plasma atomisation process produces the best powders and they provide sieving based on customer requirements. Another potential benefit of the TKF process is that the powders plastically deform at the moment of impact, which may help filling in holes in the previous layer.
I'm not as concerned about differential expansion from different materials, as I expect Titomic is using pre-alloyed powders for most, if not all applications.
Now the downside is the cost of needing high-quality powder supplies from third parties to achieve the very best material results. Titomic is investing in their own gas atomisation plant, but that doesn't have the same quality as plasma atomisation. Still, this is probably only needed for load-bearing aerospace applications, for most parts lower quality powder that still meets ASTM standards should be just fine.
I'd love to see some published papers on their work to determine the specifications and settings they used for their tests. If they outperformed ASTM standards with cheaper powders then their cost advantage would be ludicrously good.
On another note...yeah nah...I'm actually based in Australia
. The nature of the aerospace industry means you'll find plenty of American accents though, particularly at primes like Boeing and Lockheed Martin. And contrary to what some may think, there's a good reason why Boeing have subcontractors and pay CSIRO millions of dollars every year to do research rather than doing everything themselves. I've heard a Boeing person say that at any one time, they don't know what 2/3rds of their workforce are doing. That's just the nature of giant, established companies, and it makes it easier to understand how the 737 disasters happened. Not the mention the 'Senate Launch System'.....
Now while I mentioned Titomic would find better investors in the states, there are advantages to keeping some R&D in Australia. First, the government sees value-adding processes and creating an end to end supply chain for critical minerals such as titanium as a strategic priority. You can find these references in the CRC programs and previous CRC-P grant rounds. I was actually considering doing a titanium powder processing project with CSIRO for a while because of that. Also, while Australia is terrible at commercialising technology as a whole, the support for those who try is not bad. I'll use the 2.6 million agreement with CSIRO, RMIT, and the Innovative Manufacturing Cooperative Research Centre (IMCRC) as an example.
The total cost of the project is $2,611,320, and the IMCRC provided $469,748 cash. If we're being conservative and assume the universities only provided in-kind support rather than cash (still maybe worth $1,000,000), then Titomic spent $2,141,572. The vast majority of this would fall under the R&D tax rebate incentive, so ~40% of the cost is credited by the government as a CASH REFUND every financial year as Titomic is running at a loss. This means Titomic only spent ~$1,300,000 million to gain access to researchers and facilities that give an overall project value of well over $3,000,000.
As for my investment in Titomic, I will probably be reducing my position in a few months, but only because my own startup will need that capital instead. I can see myself being a customer/partner to Titomic in a few years time - I've already got one of their business cards
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