Surface engineering of tool steel & duplex stainless steel

Abstract

The approach of the present work is directed towards the tribological study of two different steel materials viz. AISI H13 tool steel majorly used in hot forging and forming industries and AISI 2205, duplex stainless steel used in petrochemical, marine, nuclear, chemical, automotive, and paper industries. AISI 2205 duplex SS steel contains nearly same amounts of austenite ‘γ’ and ferrite ‘α’ and thus, dualphase microstructure leads to an excellent combination of mechanical properties and better corrosion resistance lagging with its reliable performance against frictional forces. Surface modification of steel surfaces introduces better response against wear degradation phenomenon. Improved surface characteristic of the material was achieved by deploying different surface treatments like surface mechanical attrition treatment (SMAT), plasma-nitriding and a subsequently a duplex treatment (SMAT + plasma-nitriding). In current work, ion plasma nitriding was performed at 460oC for 5 hrs and 525oC for 10 hrs in case of H13 tool steel and DSS 2205 steel specimen, respectively. Different specimens were characterized using optical microscopy, FESEM, XRD, hardness. Plasma-nitriding introduces hard nitride layer of average thickness ≈14 µm and ≈9 µm in H13 tool steel and DSS 2205 steel specimen respectively. Surface hardness, approximately two and three times in HRC scale was achieved as a result of plasma-nitriding for H13 and DSS 2205 respectively. Fe3N, CrN and Cr2N are nitride phase was formed after the nitriding treatment in case of H13 whereas expanded austenite also present in DSS 2205 steel material. Dry-sliding wear test was performed on both bare as well as nitrided specimen using various applied load and sliding velocity. Steel surfaces with hard nitride layer shows better wear performance compared to untreated one. Plasma nitrided AISI H13 shows maximum 98% of improvement in wear resistance than as-received at 0.5 m/s sliding velocity and 15 N applied load. However, duplex treated AISI 2205 steel shows 97% enhancement in wear resistance at 1 m/s sliding velocity and 10 N applied load. Therefore, Plasma nitride AISI H13 and duplex treated AISI 2205 steels can be used in tribological applications in dry sliding conditions.