Improvement in Surface and Tribological Properties of Fe-1%C Steel Produced by Powder Metallurgy Method by Thermal Spray Coating

Abstract

In this study, the surface properties of Fe–1wt.%C based components produced by powder metallurgy (P/M) were enhanced using a NiCrBSi alloy deposited via the Powder Flame Spray (PFS) technique. Detailed examinations revealed that the inherent surface roughness of the P/M substrates promoted strong mechanical interlocking between the molten spray droplets and the substrate. X-ray diffraction (XRD) analyses confirmed the formation of Cr₂B (chromium boride) and various nickel–chromium silicide phases (Cr₃Ni₂Si and Cr₃Ni₅Si₂), which developed as a result of the rapid solidification occurring during the spraying process. Microhardness measurements indicated a significant increase in surface hardness from approximately 250 HV for the uncoated substrate to about 550 HV after coating, corresponding to an improvement of nearly 110%. This hardness level exceeds the conventional benchmark value of 40 HRC (≈400 HV), demonstrating that superior mechanical performance can be achieved through spray-induced energy transfer even in the absence of post-deposition heat treatment. Tribological evaluations showed that the coefficient of friction (COF), which ranged between 0.8 and 1.0 for the uncoated surface, was markedly reduced to approximately 0.2 with a coating thickness of 150 µm. Scanning electron microscopy (SEM) observations revealed severe material loss and deep abrasive grooves on the uncoated samples, whereas the NiCrBSi-coated surfaces maintained structural integrity owing to the presence of hard intermetallic phases, resulting in a more stable and improved wear regime. Overall, the results demonstrate that high wear resistance and low friction performance can be effectively achieved in powder metallurgy components through appropriate coating parameters, without the need for additional heat treatment.

Keywords

• Thermal Spray Coating
• NiCrBSi
• tribology
• powder metallurgy
• powder flame spray

Toz Metalurjisi Yöntemiyle Üretilen Fe-%1C Çeliğinin Yüzey ve Tribolojik Özelliklerinin Termal Püskürtme Kaplama Yöntemiyle İyileştirilmesi

Abstract

Bu çalışmada, toz metalurjisi (P/M) ile üretilen Fe–1wt.%C bazlı bileşenlerin yüzey özellikleri, Toz Alev Püskürtme (PFS) tekniğiyle kaplanmış bir NiCrBSi alaşımı kullanılarak iyileştirilmiştir. Detaylı incelemeler, P/M alt tabakalarının doğal yüzey pürüzlülüğünün, erimiş püskürtme damlacıkları ile alt tabaka arasında güçlü mekanik kenetlenmeyi teşvik ettiğini ortaya koymuştur. X-ışını kırınımı (XRD) analizleri, püskürtme işlemi sırasında meydana gelen hızlı katılaşma sonucu oluşan Cr₂B (krom borür) ve çeşitli nikel-krom silisit fazlarının (Cr₃Ni₂Si ve Cr₃Ni₅Si₂) oluşumunu doğrulamıştır. Mikro sertlik ölçümleri, kaplamasız alt tabaka için yaklaşık 250 HV olan yüzey sertliğinin, kaplamadan sonra yaklaşık 550 HV'ye yükseldiğini ve yaklaşık %110'luk bir iyileşme sağladığını göstermiştir. Bu sertlik seviyesi, geleneksel 40 HRC (≈400 HV) referans değerini aşarak, kaplama sonrası ısıl işlem olmaksızın bile püskürtme kaynaklı enerji transferi yoluyla üstün mekanik performans elde edilebileceğini göstermektedir. Tribolojik değerlendirmeler, kaplamasız yüzey için 0,8 ile 1,0 arasında değişen sürtünme katsayısının (COF), 150 µm kaplama kalınlığı ile yaklaşık 0,2'ye önemli ölçüde düştüğünü göstermiştir. Taramalı elektron mikroskobu (SEM) gözlemleri, kaplamasız numunelerde ciddi malzeme kaybı ve derin aşındırıcı oluklar ortaya koyarken, NiCrBSi kaplı yüzeyler, sert intermetalik fazların varlığı sayesinde yapısal bütünlüğünü koruyarak daha kararlı ve gelişmiş bir aşınma rejimi sağlamıştır. Genel olarak, sonuçlar, uygun kaplama parametreleri ile toz metalurjisi bileşenlerinde ek ısıl işleme gerek kalmadan yüksek aşınma direnci ve düşük sürtünme performansının etkili bir şekilde elde edilebileceğini göstermektedir.

Keywords

• Termal sprey kaplama
• NiCrBSi
• toz metalurjisi
• toz alev sprey
• triboloji

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