Effect of Boron Nitride Addition on the Microstructure and Mechanical Properties of PM Steels

Abstract

In this work, the effects of boron nitride additions on the microstructures and tensile behaviours of microalloyed powder metallurgy (PM) steels were investigated. The microstructure of the microalloyed PM steels was characterised by optic microscope, SEM and EDS. Results indicated that the addition of boron nitride in the percentage of 0.1 and 0.2 increases the yield strength (YS) and ultimate tensile strength (UTS) of the PM steels in the sintered conditions. Elongation also tends to improve with increasing boron nitride content. In addition, the presence of boron nitride in different proportion prevented grain growth during sintering or cooling after sintering. However, a further increase in BN to 0.5 wt.% reduced the yield strength (YS), ultimate tensile strength (UTS), percentage elongation and hardness due to higher amount of precipitation strengthening. Toz Metal Çeliklerin Mikroyapı ve Mekanik Özelliklerine Bor Nitrürün Etkisi Anahtar kelimeler Toz Metal Çelikler, BorNitrür, Mikroyapı, Mekanik Özellikler. ÖzetBu çalışmada, Mikroalaşımlı Toz metal (TM) çeliklerin mikroyapı ve çekme davranışları üzerine bor nitrür ilavesinin etkileri incelenmiştir. Mikroalaşımlı TM çeliklerin mikroyapıları optik mikroskop, SEM ve EDS analizleri kullanılarak karakterize edilmiştir. Sonuçlar; yüzde 0,1 ve 0,2 oranında bor nitrür ilavesinin TM çeliklerin akma dayanımını (YS) ve çekme mukavemetini (UTS) artırdığını göstermiştir. Ayrıca % Uzama oranı bor nitrür ilavesinin artmasıyla artma eğilimindedir. Buna ek olarak, farklı oranda bor nitrür varlığı sinterleme sırasında veya sinterleme sonrasında tane büyümesini engellemiştir. Ancak ağırlıkça % BN oranını 0,5 olduğunda akma dayanımı (YS), çekme dayanımı (UTS), % uzama ve sertlik değeri çökelme sertleşmesine bağlı olarak azalmıştır.

Effect of TiC, TiN, and TiCN on microstructural, mechanical and tribological properties of PM steels

“…The addition of 0.5 % TiC, TiN ve TiCN also led to an enhancement of strength. The obtained results were consistent with previous studies [16,17,25]. Ozdemir et al [25] and Erden et al [17] added NbC and BN to the iron matrix composites, respectively.…”

“…The obtained results were consistent with previous studies [16,17,25]. Ozdemir et al [25] and Erden et al [17] added NbC and BN to the iron matrix composites, respectively. Results show that NbC and BN particles were observed in SEM images and the increase in mechanical properties was attributed to dispersion strengthening of these particles.…”

“…However, a decrease in strength was observed when the reinforcement rate was increased from 0.2 to 0.5 %. It was noted that excessive precipitation at grain boundaries can cause this decline [17]. In another study, enhancement of strength of PM steel was obtained with the addition of low amount (0.1-0.2 %) titanium addition.…”