Duplex coating of AISI 316 and 420 die for hot mold stamping

Prehardened AISI-316 and AISI-420 materials are proposed as a new mold-die material especially for hot mold-stamping of oxide glasses. First, high-density plasma nitriding is developed to preharden the initial AISI-316 and AISI-420 raw materials after cleaning and polishing. The hardness range from 600 HV to 800 Hv is attained by this plasma nitriding in relatively low temperature. In second, this prehardened substrates are further DLC-coated by using the RF-sputtering or unbalanced magnetron sputtering. The thickness of coating is kept to be nearly constant by 0.4 to 0.6 mm. In addition to hardness testing, tribological testing is also performed to prove that low frictional state by m = 0.1 to 0.15 should be attained by this duplex coating. In final, optical polymers and oxide glasses are employed to make mold-stamping test to demonstrate the high temperature strength of this duplex-coated mold die.