Microstructure Characterization and Corrosion Properties of Nitrocarburized AISI 4140 Low Alloy Steel

作者：Fattah M^*; Mahboubi F

来源：Journal of Materials Engineering and Performance, 2012, 21(4): 548-552.

DOI：10.1007/s11665-011-9922-3

• AISI 4140 steel
• austenitic plasma nitrocarburizing
• corrosion resistance
• electrochemical property
• ferritic plasma nitrocarburizing
• hardness

Plasma nitrocarburizing treatments of AISI 4140 low alloy steel have been carried out in a gas mixture of 85% N-2-12% H-2-3% CO2. All treatments were performed for 5 h at a chamber pressure of 4 mbar. Different treatment temperatures varying from 520 to 620 A degrees C have been used to investigate the effect of treatment temperature on the corrosion and hardness properties and also microstructure of the plasma nitrocarburized steel. Scanning electron and optical microscopy, x-ray diffraction, microhardness measurement, and potentiodynamic polarization technique in 3.5% NaCl solution were used to study the treated surfaces. The results revealed that plasma nitrocarburizing at temperatures below 570 A degrees C can readily produce a monophase epsilon compound layer. The compound layer formed at 620 A degrees C is composed of two sub-layers and is supported by an austenite zone followed by the diffusion layer. The thickest diffusion layer was related to the sample treated at 620 A degrees C. Microhardness results showed a reduction of surface hardness with increasing the treatment temperature from 520 to 620 A degrees C. It has also been found that with increasing treatment temperature from 520 to 545 A degrees C the corrosion resistance increases up to a maximum and then decreases with further increasing treatment temperature from 545 to 620 A degrees C.

• 出版日期2012-4