Surface Coating on Cold Work Tool steel AISI D 2 using Packed Boriding Process with Applied Direct current

Recently, a cold work tool steel AISI D2 is used normally for metal forming process which surface damage is found frequently. Thus, surface treatments to improve a tool life are performed generally on tool steels before an operating process. A packed boriding process is one of the most well-known thermochemical surface treatments which possess a very high hardness layer at the surface. However, the boriding process has to operate at a high temperature with a prolonged soaking time to create a greater thickness taking into account the diffusion theory. An applied direct current field is a possible method to enhance diffusion rate of boron atom. For this reason, in this research, effects of an applied direct current field during boring process was investigated on the cold work tool steel AISI D2 by the การประชุมวิชาการข่ายงานวิศวกรรมอุตสาหการ ประจ าปี พ.ศ. 2555 17-19 ตุลาคม 2555 ชะอ า เพชรบุร ี 1537 applied direct current in the range of 0-5.5 A at a temperature of 900 C with boriding time of 4 hr. Afterwards, microstructure and hardness values were investigated using optical microscope and microvicker harness tester, respectively. It was found that a double phase (FeB and Fe2B) was detected on the boride layer. The near surface hardness value of about 1800 HV was measured A greater thickness of boride layer was detected if a direct current was applied.