Pack-Boronizing of AISI 4140 Steel: Boronizing Mechanism and the Role of Container Design

Abstract

In this study, pack-boronizing of AISI 4140 steel was done. Three mild-steel containers with different size, namely, small-size container (SC), medium-size container (MC), and big-size container (BC) were used. Steel specimens were boronized at 950°C for 2 or 3 h. Preconditioning of the containers was observed to be essential before doing final pack-boronizing of steel. MC was found suitable for the formation of monophase Fe₂B layer while BC produced unwanted FeB phase along with Fe₂B layer. Fe₂B phase showed the columnar morphology. Continuous decrease in the hardness from surface to nonboronized core was observed. Maximum surface hardness of about 1367 HV_0.1 was obtained (hardness of nonboronized core was about 252 HV_0.1) for the boronized steel. As compared to the normalized and hardened–tempered (HT) AISI 4140 steel pins, boronized steel pin showed the lowest “specific wear rate” (0.89 × 10⁻⁶ mm³/Nm) and coefficient of friction (COF) (0.55).

Keywords:

• Alloys
• Boride
• Boron
• Hardening
• Hardness
• Microstructure
• Morphology
• Steel

Notes

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