Effects of Titanium Nitride Surface Coating on High Speed Impact Induced Damage of Magnesium Alloys at Cryogenic Temperature

This reports a summary of our recent high speed impact tests aiming to clarify the impact characteristic of magnesium alloy with titanium nitride coating. We placed 100 mm x 100 mm and 3 mm thick magnesium alloy plates, ZK60A-T5 at 298 K, 223 K and 153 K, which were coated with 1 micron thick titanium nitride layer based on a hollow cathode discharge method. We also tested with uncoated magnesium plates. The plates were impinged by 8 mm diameter aluminum alloy (Al2017-T4) spheres at impact speeds of 0.5 to 1.7 km/s in a two-stage light gas gun in the SWRC, IFS, Tohoku Univ. Two specimens were installed at 100 mm interval vertically to the spheres in a cryogenic test chamber [1]. Impact phenomena were visualized with shadowgraph arrangements and recorded with ImaCon 200. As a result, the effect of surface coating on surface fracture was examined. We found the increase of hole areas in proportional to the impact speed and a clear difference of penetration hole and fracture patterns between impact speed of 0.5 km/s and higher impact speeds.~The titanium nitride coating was effective to favorably control the damage process. [1] Numata,D. et al., Shock Waves (2008), 18:169-183.