METHOD FOR DUPLEX SURFACE THERMAL TREATMENT BY PLASMA STEEL GRADE OF AN H13 TOOL.

摘要

The present invention discloses a duplex plasma treatment method for a grade steel of an H13 tool, which comprises a first step of plasma heat treatment in a temperature range of up 470°C to 530°C, for four hours at a two Torr pressure. All of that in a gaseous atmosphere of nitrogen and hydrogen, at a current density of up between 1.0 mA / cm2. The said first stage promotes the formation of a surface layer consisting of Fe3N and Fen type iron nitrides. Also, it comprises a second step by plasma heat treatment in a temperature range of up 470°C to 530°C for one hour at a two Torr pressure in a gaseous atmosphere of oxygen and hydrogen, using a current density of up to 0.5 mA /cm2. This second step promotes the formation of a layer of surface oxides of the type Fe2O3 and Fe3O4. The pieces treated under the duplex treatment exhibit a decrease in the value of the friction coefficient at 37.5% concerning the untreated material and 40% of the value obtained for the nitride material, and co ncerning the surface hardness, it exhibits properties with values at 190% of above the untreated material.