TWI Industrial Member Report Summary 1031/2013
By R. Fairclough, P. McNutt
In this report, two titanium alloys are examined to investigate their suitability for laser metal deposition. These are Ti-8Al-1Mo-1V (Ti-811), a near ? alloy and Ti-5Al-5V-5Mo-3Cr (Ti-5553), a near ? alloy. A nickel-based alloy, Mar-M247, is also used as a candidate material due to its high aluminium and titanium content which makes it very susceptible to crack formation and propagation during high temperature processing.
There is an industry requirement to repair and refurbish aerospace components which are manufactured from the latest types of high strength alloys. The materials investigated in this report fall into this category and development of techniques to successfully repair them could offer substantial cost savings in the overhaul of aero-engines and structural components.
- Both Titanium alloys deposited very well, producing test blocks that were shown to be fully dense and free from cracks and fusion defects.
- The as deposited microstructure of Ti-5553 consisted of large columnar and equiaxed prior ? grains, which following heat treatment consisted of large prior ? grains separated by grain boundary ?, with precipitation of very fine scale a inside the ? grain.
- The as deposited microstructure of Ti-811 consisted of massive prior ? grains containing fine acicular ? and heat treatment increased the volume fraction of ? from approximately 65% in the as deposited state to 92%.
- It was not possible to deposit Mar-M247 without severe cracking, using any parameter combination, with crack propagation being inter-granular and appearing to follow the dendrites, possibly using MC carbides to aid propagation
- Deposition of Mar-M247 at higher laser power appears to decrease the crack density, but not to a point that could be considered a success