Scientists in northwest China have doubled the service life of high-temperature, high-pressure artillery barrels by refining a chromium plating technique first used by the Chinese military before 200BC.
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Bronze swords buried with the Terracotta Army of China’s first emperor, Qin Shi Huang, remained sharp and untarnished after more than 2,000 years underground.
Microscopic analysis revealed a thin layer of chromium salts – just 10 to 15 micrometres thick – on their surfaces, protected by an underlying oxide film that had all but halted corrosion, seen as evidence of a sophisticated surface treatment technique mastered by ancient Chinese metallurgists.
According to a study published in the July issue of Acta Armamentarii, China’s top defence tech journal, researchers have now upgraded this ancient method into a cutting-edge solution for one of modern artillery’s most persistent challenges – barrel erosion.
High-velocity cannons and advanced howitzers face extreme conditions with every firing. Inside the barrel, temperatures soar past 3,000 degrees Celsius (5,432 degrees Fahrenheit) and pressures exceed tens of thousands of atmospheres.
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The combined effect of chemical erosion from propellant gases, mechanical abrasion from projectiles and thermal shock from repeated firings leads to rapid wear, microcracking and eventual degradation of the bore.