Surface chemical analysis of prealloyed water atomised steel powder

Karlsson, Henrik; Nyborg, Lars; Berg, Sigurd

doi:10.1179/0032589005x37675

Cited by 66 publications

(55 citation statements)

References 20 publications

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“…The strength of the latter indicates that the surface of the powder was covered with an oxide layer, which likely consisted mostly of Fe oxides based on the strength of the Fe peak. The minute Cr peak does, however, suggest that at least some Cr oxide was also present, with the lower peak intensity likely caused by interference from the O and Fe peaks [6]. Depth profiling by AES can be used to determine the extent to which this oxide layer extends from the surface, with Figure 3 showing the change in Fe, O and Cr with analysis time and particle depth.…”

Section: Aes Analysismentioning

confidence: 99%

“…This facilitates powder compaction, gives good green body strength and makes the powder suitable for near-net shaping of components [6]. However, the interaction of molten metal droplets with water or steam inevitably creates a surface oxide layer during atomization [6][7], and so subsequent reduction is needed to obtain high-purity powder. In this pre-alloyed state, Cr is usually present in solid solution with iron, and so its activity is roughly equal to its content [5].…”

Section: Introductionmentioning

confidence: 99%

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Carbon Co-Deposition During Gas Reduction of Water-Atomized Fe-Cr-Mo Powder

Ali

Choi

Seo

et al. 2017

Archives of Metallurgy and Materials

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The water atomization of iron powder with a composition of Fe-3Cr-0.5Mo (wt.%) at 1600°C and 150 bar creates an oxide layer, which in this study was reduced using a mixture of methane (CH 4 ) and argon (Ar) gas. The lowest oxygen content was achieved with a 100 cc/min flow rate of CH 4 , but this also resulted in a co-deposition of carbon due to the cracking of CH 4 . This carbon can be used directly to create high-quality, sinter hardenable steel, thereby eliminating the need for an additional mixing step prior to sintering. An exponential relationship was found to exist between the CH 4 gas flow rate and carbon content of the powder, meaning that its composition can be easily controlled to suit a variety of different applications.

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Section: Aes Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Carbon Co-Deposition During Gas Reduction of Water-Atomized Fe-Cr-Mo Powder

Ali

Choi

Seo

et al. 2017

Archives of Metallurgy and Materials

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“…In the case of chromium, and being a big difference the Mo base steels of similar characteristics, it can be obtained special steels devoted for carbonitriding or nitriding [83,84]. But the implementation of Cr or Mn in large scale production, despite their fantastic effect on hardenability [85,86], has been limited by their high affinity for the oxygen and the difficulties to reduce de amount of this element.…”

Section: High Oxygen Affinity Alloying Elementsmentioning

confidence: 99%

“…They are cheap materials, abundant, easy to recycle and improve the properties of steels as alloying elements. Their high affinity for the oxygen and the poor control in the atmospheres till mid 90"s, most of these trials have tested through the additions of ferroalloys [73,74,75,76] or master alloys [77,78,79,80,81,82] to reduce their activity during sintering.In the case of chromium, and being a big difference the Mo base steels of similar characteristics, it can be obtained special steels devoted for carbonitriding or nitriding [83,84]. But the implementation of Cr or Mn in large scale production, despite their fantastic effect on hardenability [85,86], has been limited by their high affinity for the oxygen and the difficulties to reduce de amount of this element.…”

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confidence: 99%

From Sintered Iron to High Performance PM Steels

Torralba

Oro

Campos

2011

MSF

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Keywords: powder metallurgy steels, low alloyed steels, high performance, master alloys.Abstract. Since low alloyed sintered steels were introduced in the market of the structural parts, we have followed the evolution of a material with poor mechanical properties and any uniformity (in the sense of reproducibility) to materials that today are produced with high reliability and performance. The working efficiency could be equivalent in many cases with the best wrought steel, and maintaining a good margin in terms of cost and competitively. In this paper a complete review of the topic is accomplished, from the early times when the first parts were made by plain iron or iron-carbon, going through the different alloying systems: Fe-Cu, Fe-P, Fe-Cu-Ni-Mo, and more recently Fe-Cr-Mo and Fe-Mn. The development in processing routes has been considered too. The main milestones in the field of new alloying systems have been: 1) the introduction of Cu in 60-70"s, 2) the new complex systems with Cu-Ni-Mo in the 80"s and 3) the introduction of alloying elements with high oxygen affinity (in the late 90"s). Regarding the milestones in processing could be considered: 1) the development of new mixing procedures, 2) the warm compaction and high velocity compaction, 3) the improvements in sintering control and high temperature sintering. Several decades of research and innovation, acting on the processing system (mixing, pressing, sintering, post-sintering operations,…) and on the alloying system (from the earliest times with plain iron to complex systems used today), has allowed us to have a highly competitive materials, in terms of performance, and processes in terms of cost. The future is still open to new developments. First sintered steels.Iron based powder metallurgy (PM), were developed in the previous years to the II World War, being the absence of raw materials the pushing effect, and it was the origin of a new materials family (PM Steels) that today can be considered a high performance materials. The first sintered part was introduced in the car industry by General Motors in 1937 and was an oil gear for oil pump [1]. One of the first components introduced was one iron part for an electrical engine in 1945 [2].Till late 60"s were manufactured by PM simple parts, that were based on Fe-C and Fe-Cu-C systems. The knowledge of these systems was developed from works that analyze the possible formation of liquid phase during sintering with the aim of improving the densification and to promote sintering activation [3] as well the diffusion mechanisms in plain systems and selfdiffusion of Fe [4,5]. To analyze and to understand the sintering steps were use iron wires that can reproduce the sintering model based on spheres [6].Looking for the improvement in the mechanical properties, at that time considering the available technology two basic requirements for new alloying systems were stated: poor or null affinity for the oxygen -sintering atmospheres were not enough dried [7]-and the possibility of controlling dimensionally the s...

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“…5a for mixes containing water-atomized metallic Fe with 0.5 mass/% graphite. The surface of different Fe-based atomized powders has been characterized in several studies by Nyborg et al using surface sensitive analysis techniques [18][19][20][21]. Water-atomized powders are typically covered by a homogeneous iron oxide layer formed by Fe 2 O 3 with a thickness of around 6-8 nm and disperse particulate oxides of a higher stability (mainly Cr-, Mn-and Si-containing oxides) with an average size of 200 nm [22].…”

Section: °Cmentioning

confidence: 99%

Application of thermal analysis techniques to study the oxidation/reduction phenomena during sintering of steels containing oxygen-sensitive alloying elements

Calderon

Gierl‐Mayer

Danninger

2016

J Therm Anal Calorim

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For the consolidation of steel parts manufactured by powder metallurgy (PM) techniques, removal of the surface oxides covering metallic powder particles is a necessary prerequisite. In PM steels with conventional compositions, reduction of the oxides is easily achieved in traditional sintering furnaces. However, processing steels containing alloying elements with a high oxygen affinity represents a big challenge that requires a deeper understanding of the chemical processes occurring during sintering. In the present work, thermogravimetry analysis coupled with mass spectrometry is used to describe the oxidation/reduction phenomena that take place when sintering steel powders and how these processes are modified by the addition of admixed particles containing oxygensensitive elements. Carbothermal reduction processes are studied using pure oxides (Fe 2 O 3 , MnO 2 , Cr 2 O 3 and SiO 2 ) as well as water-atomized Fe powders mixed with small amounts-4 mass/%-of Cr, Mn and Si powders or FeMn-Si-(Cr) master alloy powders. The results show that there is an oxygen transfer from the base iron particles to the oxidation-sensitive elements-''internal getter effect''-taking place mostly through the gas phase. Different alloying elements (Cr, Mn, Si) show different temperature ranges of susceptibility to oxidation. Combination of these oxygen-sensitive alloying elements in the form of a master alloy powder reduces their sensitivity to oxidation. Also, the use of master alloys promotes the concentration of the oxides on the surface of the alloying particles and not in the grain boundaries of the surrounding iron particlesas occurs when using Mn carriers-which should have a beneficial impact on the final mechanical performance.

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Surface chemical analysis of prealloyed water atomised steel powder

Cited by 66 publications

References 20 publications

Carbon Co-Deposition During Gas Reduction of Water-Atomized Fe-Cr-Mo Powder

Carbon Co-Deposition During Gas Reduction of Water-Atomized Fe-Cr-Mo Powder

From Sintered Iron to High Performance PM Steels

Application of thermal analysis techniques to study the oxidation/reduction phenomena during sintering of steels containing oxygen-sensitive alloying elements

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