| 1. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Characterization of surface oxides on water-atomized steel powder by XPS/AES depth profiling and nano-scale lateral surface analysis
- 2013
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332. ; 268, s. 496-506
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Tidskriftsartikel (refereegranskat)abstract
- Characterization of oxide products on the surface of water-atomized steel powder is essential in order to determine the reducing conditions required for their removal during the sintering stage which in turn will result in improved mechanical properties. Pre-alloyed powder with 3 wt% Cr and 0.5 wt% Mo was chosen as the model material. Investigation of the powder surface characteristics with regard to composition, morphology, size and distribution of surface oxides was performed using X-ray photoelectron spectroscopy, Auger electron spectroscopy and high resolution scanning electron microscopy combined with X-ray microanalysis. The analysis revealed that the powder is covered by a homogeneous (similar to 6 nm thick) Fe-oxide layer to similar to 94% whereas the rest is covered by fine particulate features with the size below 500 nm. These particulates were further analyzed and were divided into three main categories (i) Cr-based oxides with simultaneous presence of nitrogen, (ii) Si-based oxides of "hemispherical" shape and (iii) agglomerates of the afore mentioned oxides.
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| 2. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Effect of Atmosphere Composition on the Surface Interactions during Sintering of Chromium-alloyed PM Steels
- 2011
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Ingår i: Proceedings of EURO PM 2011 International Powder Metallurgy Congress & Exhibition, 9th-12th October 2011, Barcelona. - 9781899072231 ; 3, s. 111-117
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Konferensbidrag (refereegranskat)abstract
- Chromium is extensively used today in PM steels, nevertheless its high affinity to oxygen requires strict atmosphere control during the sintering process. Nitrogen-based atmospheres with different hydrogen contents (0, 3 and 10%H2) were used during sintering of chromium-alloyed water atomized steel powders with continuous atmosphere monitoring in the sintering furnace. Fracture surface of pressed and sintered specimens were studied using high resolution scanning electron microscopy (HRSEM) equipped with EDX in order to investigate the development and characteristics of the reaction products formed. The investigation was complemented with thermal analysis using DTA/TG. The formation of particulate reaction products containing strong-oxide forming elements such as Cr, Si and Mn was detected for all conditions. Enhanced oxide reduction was observed in samples processed in hydrogen containing atmospheres independently of the actual content. Obtained results show that significant reduction of the oxygen content can be achieved by adjusting the atmosphere purity/composition.
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| 3. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Effect of process parameters on surface oxides on chromium-alloyed steel powder during sintering
- 2013
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Ingår i: Materials Chemistry and Physics. - : Elsevier BV. - 0254-0584. ; 138:1, s. 405-415
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Tidskriftsartikel (refereegranskat)abstract
- The use of chromium in the PM steel industry today puts high demands on the choice and control of theatmosphere during the sintering process due to its high affinity to oxygen. Particular attention is requiredin order to control the surface chemistry of the powder which in turn is the key factor for the successfulsintering and production of PM parts. Different atmosphere compositions, heating rates and greendensities were employed while performing sintering trials on water atomized steel powder pre-alloyedwith 3 wt.% Cr in order to evaluate the effect on surface chemical reactions. Fracture surfaces of sinteredsamples were examined using high resolution scanning electron microscopy combined with X-raymicroanalysis. The investigation was complemented with thermogravimetric (TG) studies. Reactionproducts in particulate form containing strong-oxide forming elements such as Cr, Si and Mn wereformed during sintering for all conditions. Processing in vacuum results in intensive inter-particle neckdevelopment during the heating stage and consequently in the excessive enclosure of surface oxidewhich is reflected in less good final mechanical properties. Enhanced oxide reduction was observed insamples processed in hydrogen-containing atmospheres independent of the actual content in the rangeof 3e10 vol.%. An optimum heating rate was required for balancing reduction/oxidation processes. Asimple model for the enclosure and growth of oxide inclusions during the sinter-neck development isproposed. The obtained results show that significant reduction of the oxygen content can be achieved byadjusting the atmosphere purity/composition.
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| 4. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Effect of reducing agents on the sintering of chromium alloyed PM steels
- 2013
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Ingår i: Proceedings EURO PM2013 Congress & Exhibition, 15-18 September 2013, Gothenburg, Sweden. - : European Powder Metallurgy Association (EPMA). ; 2, s. 297-302
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Konferensbidrag (refereegranskat)abstract
- The control of the surface chemistry during sintering is the key factor for the successful and efficientproduction of PM parts, especially for powders containing elements with high affinity to oxygen such as chromium.The effect of different reducing agents was investigated by performing sintering trials on water atomized steel powder pre-alloyed with 3 wt.% Cr with and without the addition of graphite as well as using atmospheres with varying hydrogen content. The use of thermal analysis and photoacoustic spectroscopy in combination with results from fractographic investigation showed that oxide reduction is enhanced with the presence of hydrogen even if the main reduction mechanism is the carbothermal reactions. Oxides rich in Cr, Mn and Si were formed during sintering for all appliedconditions. The findings are summarized in a simple model describing the enclosure of oxides during the sinter-neckdevelopment and the changes in surface chemistry during the process.
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| 5. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Effect of Sintering Atmosphere on the Transformation of Surface Oxides during the Sintering of Chromium Alloyed Steel
- 2010
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Ingår i: Powder Metallurgy Progress. - 1335-8987. ; 9(2009):3, s. 141-155
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Tidskriftsartikel (refereegranskat)abstract
- Chromium is the one of the most attractive alloying elements for PM steels. Nevertheless, its high affinity to oxygen during sintering, especially during the heating stage, has to be considered. The present study relates surface products formation and their transformation to the employed sintering atmosphere. The study consists of the investigation of the type, morphology and distribution of reaction products on the fracture surfaces of specimens pressed and sintered at different temperatures between 700 and 1200°C, for various times, as well as the evaluation of the metal surface – sintering atmosphere interactions in terms of gas composition and temperature. Specimens were sintered in three different atmospheres - nitrogen, nitrogen/10% hydrogen and vacuum. Fractographic investigation of fracture surfaces of specimens sampled at different temperatures, by means of HR SEM combined with EDX analysis, show that the presence of hydrogen has clearly a positive effect on the early reduction of surface iron oxide during the heating stage, which is reflected in lower amounts of oxides present as well as lower carbon loss after sintering. The amount of oxide inclusions is higher after high temperature sintering in the case of vacuum due to pronounced development of inter-particle connections during the heating stage, above 900°C, which led to enclosure of the surface oxide layer inside the necks. A change in the morphology and size of oxide inclusions was observed during the heating stage and after sintering the oxides were mainly encountered as small (
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| 6. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Efficient Sintering of Cr-Prealloyed Powders by Careful Adjustment of Process Parameters
- 2014
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Ingår i: Advances in Powder Metallurgy & Particulate Materials-2014. - 9780985339760 ; 5, s. 142-153
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Konferensbidrag (refereegranskat)abstract
- Controlling the surface chemistry during sintering is of paramount importance for the production of PM parts from powders containing oxidation sensitive elements such as Cr. Sintering trials were performed on compacts from water atomized steel powder pre-alloyed with 3 wt.% Cr. Two different compact densities and three different heating rates were investigated in order to evaluate the effect of these process properties in connection with the sintering atmosphere. Using thermal analysis and photoacoustic spectroscopy in combination with results from the fractographic investigations showed that increasing the heating rate up to a certain extent leads to decreased enclosure of surface oxide inside the developing sinter necks. For the samples of higher density the less efficient atmosphere replenishment is responsiblöe for the larger amounts of enclosed Cr-Mn-Si-rich oxides encountered inside the sinter necks. The adjustment of the process parameters in line with the sample density leads to improved mechanical performance.
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| 7. |
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| 8. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Fractographic Investigation of Chromium-alloyed PM Steels Sintered in Atmospheres with Varying Hydrogen Content
- 2011
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Ingår i: Powder Metallurgy Progress. - 1335-8987. ; 11:1-2, s. 32-41
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Tidskriftsartikel (refereegranskat)abstract
- Chromium usage in PM steels is extensive today due its attractive properties. On the other hand its high affinity to oxygen requires a strict control over the sintering atmosphere used. In order to investigate the effect of the atmosphere composition in terms of hydrogen content (0%-3%-10%) on the characteristics of the reaction products, the fracture surface of pressed and sintered specimens of chromium-alloyed water atomized steel powders was studied using high resolution scanning electron microscopy combined with energy dispersive EDX analysis (SEM+EDX). For all applied conditions the formation of particulate reaction products, rich in strong oxide-forming elements, was identified. The oxide reduction was enhanced in the samples processed in hydrogen containing atmospheres. The study shows that careful adjustment of the sintering atmosphere in terms of purity and composition leads to the significant reduction of the oxides content and so better developed inter-particle necks.
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| 9. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Methodology for Evaluating the Oxide Distribution in Water Atomized Steel Powder
- 2009
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Ingår i: Proceedings of EURO PM 2009 International Powder Metallurgy Congress & Exhibition. - 9781899072071 ; 2, s. 181-186
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Konferensbidrag (refereegranskat)abstract
- A method for characterizing the oxide composition and distribution in both the surface and the interior of water-atomized powder was developed. Pre-alloyed powder with 3wt.% Cr and 0.5 wt.% Mo was chosen as the model material. Surface sensitive analytical techniques (high resolution electron microscopy in combination with EDX-analysis, X-ray photoelectron spectroscopy and Auger electron spectroscopy) were used in order to study the type, composition, morphology and distribution of oxide products. The analysis revealed that the powder particles were mainly covered by a homogeneous (~6 nm) thick Fe-oxide layer and some spherical particulate features with size up to 200 nm that were complex Fe-Cr-Mn-Si-oxides. Using EDX Smart-Maps tool, inclusions below 1μm in size and rich in Cr and Mn were observed rarely in the interior of the powder particles. By means of the method, the distribution of surface bound and bulk oxygen is realised.
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| 10. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Optimisation of sintering atmospheres for controlled sintering of PM steels
- 2013
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Ingår i: Proceedings EURO PM2013 Congress & Exhibition, 15-18 September 2013, Gothenburg, Sweden. - : European Powder Metallurgy Association (EPMA). ; 2, s. 339-346
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Konferensbidrag (refereegranskat)abstract
- The use of elements with high oxygen affinity such as Cr or Mn in PM steels has been met with skepticism although such grades are attractive options for structural applications. They require strict control of the used atmosphere during the sintering process. Various techniques such asphotoacoustic spectroscopy (PAS) and continuous CO/CO2/H2O measurements have been implemented for atmosphere monitoring during sintering trials of Cr-alloyed steel powder. The used atmospheres were nitrogen-hydrogen blends (0,3,10 and 100% H2) as well as vacuum. The progress of the oxidation/reduction processes was also followed with thermogravimetric studies. The pressed and sintered samples were examined using optical and electron microscopy in combination with EDX in order to evaluate the formed reaction products. The presence of hydrogen, even in smallamounts, is positive for the oxide reduction. Results show that careful adjustment of the used atmosphere leads to efficient production of steel components based on Cr -prealloyed powders.
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| 11. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Oxide Distribution in Prealloyed Water Atomized Steel Powder
- 2010
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Ingår i: World Powder Metallurgy Congress and Exhibition, World PM 2010; Florence; Italy; 10 October 2010 through 14 October 2010. - 9781899072194 ; 1, s. 61-69
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Konferensbidrag (refereegranskat)abstract
- A method for evaluation of the oxygen distribution in both the surface and the interior of water-atomized powder was developed. Pre-alloyed powder with 3wt.% Cr and 0.5 wt.% Mo was chosen as the model material. Surface chemical composition with regard to composition, morphology, size and distribution of surface oxides was studied by means of surface analytical techniques (XPS, Auger, SEM and EDX). The analysis revealed that the powder particles are covered by a homogeneous (~6 nm thick) Fe-oxide layer and some spherical particulate features with size up to 200 nm that were complex Fe-Cr-Mn-Si-oxides, surface coverage of which is
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| 12. |
- Chasoglou, Dimitris, 1982
(författare)
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Surface Characteristics of Water Atomized Pre-alloyed Steel Powders and their effect on Sintering
- 2010
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Powder Metallurgy (PM) is an efficient method, in terms of cost and raw material utilization, for the production of structural parts that have strict dimensional tolerances and complex geometries. In the common processing route, steel powder is fabricated by water atomization and then pressed and sintered into the final component. Due to the production method the powder surface is covered by a surface oxide that plays a vital role in the development of inter-particle connections during the sintering and thus on the final properties of the part. The materials under investigation are Cr-alloyed PM steels. The aim is to first establish a solid methodology for evaluating the surface characteristics of metal powders by means of surface sensitive analytical techniques like X-ray photoelectron spectroscopy, Auger electron spectroscopy and scanning electron microscopy combined with X-ray microanalysis. Focus was also put into investigating the oxide distribution in the interior of the powder. The analysis revealed that the powder particles were mainly covered by a homogeneous thin (~6 nm) Fe-oxide layer and some spherical particulate features with size up to 200 nm that were complex Fe-Cr-Mn-Si-oxides. Additionally inclusions below 1μm in size and rich in Cr and Mn were observed rarely in the interior of the powder. During sintering the surface oxide undergoes some changes which depend on the sintering temperature and time and the sintering atmosphere. The presence of hydrogen in the sintering atmosphere has a clear positive effect on the early reduction of surface iron oxide during the heating stage, which is reflected on lower amount of oxides present as well as carbon loss after sintering. In the case of vacuum pronounced development of inter-particle connections during the heating stage above 900°C leads to early enclosure of surface oxide layer inside the necks. As a consequence a larger amount of inclusions and agglomerates is observed after sintering. The morphology and size of oxide inclusions change during the heating stage and after sintering they were mainly encountered as small (
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| 13. |
- Chasoglou, Dimitris, 1982
(författare)
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Surface Chemical Characteristics of Chromium-alloyed Steel Powder and the Role of Process Parameters during Sintering
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Powder Metallurgy (PM) is a cost efficient method suitable for sustainable production of structural parts that have strict dimensional tolerances and complex geometries. It has been a common practice to utilize Ni and Cu as alloying elements in PM steels, but the high and fluctuating prices of Ni and the concerns around it associated with health hazards as well as the difficulty in recycling Cu lead the PM industry to search for effective alternatives such as Cr and Mn. However the use of Cr has been met with scepticism due to its affinity to oxygen which can lead to the formation of stable oxides on the powder surface. Such oxides can act as barriers for the development of sinter necks and as a consequence they are of major importance for the production of structural components through the press-and-sinter route. Thus particular attention is required in order to control the surface chemistry of the powder which is the key factor for the successful sintering and production of PM parts. The research work presented in this thesis was aimed at acquiring fundamental knowledge concerning the surface chemistry of metal powder and how it changes during the heating/sintering stage and finally how and why different process parameters can affect the reduction/oxidation mechanisms and thus the mechanical performance of the sintered part. High-resolution analytical techniques (scanning electron microscopy with X-ray microanalysis, X-ray photoelectron spectroscopy and Auger nanoprobe analysis) were used to investigate the powder surface characteristics with regard to composition, morphology, size and distribution of surface oxides. It was revealed that the Cr-alloyed powder is predominantly covered by a homogeneous (~6 nm thick) Fe-oxide layer up to ~94% whereas the rest is covered by fine particulate features with size below 500 nm which were rich in strong oxide forming elements such as Cr, Mn and Si. Hence, most of the contacts between the metal particles comprising the compacted powder will be comprised of Fe-oxide rather than the more stable oxides.Sintering trials on water atomized steel powder grades pre-alloyed with Cr using varying process parameters showed that the most critical stage is during the heating between 800-1000ºC due to the risk of enclosure of surface oxide inside the developing inter-particle connections and further transformation of any residual Fe-based oxides into the more stable Cr-Mn-spinels which at elevated temperatures can coalesce into larger agglomerates. The balance between the developed “microclimate” and the mass transport phenomena is the decisive factor for the efficient reduction of the surface oxide and is greatly affected by the existing conditions such as the atmosphere composition and temperature as well as the different process parameters like the heating rate and green density. Provided that proper pre-cautions are taken in this respect, good mechanical performance of the produced component can be achieved.
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| 14. |
- Chasoglou, Dimitris, 1982, et al.
(författare)
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Surface Interactions during Sintering of Chromium-alloyed PM Steels in Different Atmospheres
- 2010
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Ingår i: World Powder Metallurgy Congress and Exhibition, World PM 2010; Florence; Italy; 10 October 2010 through 14 October 2010. - 9781899072194 ; 2, s. 3-12
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Konferensbidrag (refereegranskat)abstract
- Chromium is the one of the most attractive alloying elements in PM steels, nevertheless its high affinity to oxygen during sintering, especially during the heating stage, have to be considered. The type, morphology and distribution of the reaction products on the fracture surface of the pressed and sintered specimens of chromium-alloyed water atomized steel powders were studied by means of high resolution scanning electron microscopy (SEM including EDX). Specimens were sintered in three different atmospheres – nitrogen, nitrogen/10%hydrogen and vacuum. In all materials formation of particulate reaction products containing strong-oxide forming elements such as Cr, Si and Mn was detected. Positive effect of hydrogen on the oxides reduction during heating stage was observed. Preferred location of the inclusions inside the dimples of inter-particle ductile fracture indicates that they originate from fine particulates on the original powder surface that were enclosed during heating stage. Obtained results indicate that oxygen content can be significantly reduced by adjustment proper atmosphere purity/composition or high-temperature sintering.
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| 15. |
- Hryha, Eduard, 1980, et al.
(författare)
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Hot Isostatic Pressing of the Water Atomized Steel Powder: Possibilities and Challenges
- 2018
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Ingår i: 2018 World Congress on Powder Metallurgy. ; , s. 286-291
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Konferensbidrag (refereegranskat)abstract
- Gas atomization provides spherical powder with the high purity and hence these grades are typically used for hot isostatic pressing. Water atomized steel powder is significantly cheaper but has some drawbacks when it comes to the powder purity, irregular powder surface, difficulty to produce high alloyed materials, etc. Recent advancement in the water atomization allows manufacturing of iron and low-alloyed steel powders with the purity, close to gas atomized powder from the surface oxide composition point of view. The presented paper reviews the potential of application of the water atomized steel powders for HIP, advantages and challenges connected to the application of such a material. As the model material, industrial water atomized steel powder, prealloyed with 3 wt.% Cr and 0.5 wt.% Mo, is used in this study. Graphite powder is admixed to the base powder (0.4 wt.%) in order to achieve required steel composition and further HIPed as well. Microstructure and fracture surface of the HIPed material are studied in details. The mechanical properties of the HIPed material are evaluated and results are discussed with regard to the influence of residual surface oxides and microstructure. Results indicate that full density components can be easily obtained in case of water atomized powder with the good mechanical performance. Further efforts to improve powder filling are necessary to get full advantage of the HIPing of water atomized powders.
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| 16. |
- Magnusson, Hans, et al.
(författare)
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Atmosphere control during hot isostatic pressing of capsule-free materials
- 2019
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Ingår i: Euro PM 2019 Congress and Exhibition.
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Konferensbidrag (refereegranskat)abstract
- Producing components via powder yields a final product with few process steps. In order to get improved mechanical properties, final consolidation using hot isostatic pressing (HIP) is often performed. In this work, the aim is to include atmosphere control for HIP of capsule-free materials, e.g., additively manufactured components or conventionally pressed and sintered materials. Atmosphere control is applied for various purposes, such as carburising, e.g., traditional case hardening, or introducing an inert furnace atmosphere for HIP of sensitive materials. Carburisation experiments have been performed in a HIP-unit using methane as carbon source. The material response has been evaluated based on varying ratios of methane, time for carburising, ingoing densities, and alloy composition. The results show that porosity has a strong influence on carbon uptake, and lower density yields more carbon. As expected, a strong relation between added methane content and carbon uptake is also seen. Carburisation times of a few minutes gave little effect, however, 60 minutes gave approximately 500µm carburisation depth.
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| 17. |
- Magnusson, Hans, et al.
(författare)
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Atmosphere control during hot isostatic pressing of capsule free materials
- 2020
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Ingår i: Proceedings - Euro PM2020 Congress and Exhibition.
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Konferensbidrag (refereegranskat)abstract
- Producing components via powder metallurgy yields a final product with few process steps. In order to get improved mechanical properties, a final compaction using hot isostatic pressing (HIP) is often made. Capsule free HIP can be used for components produced via consolidation processes that yield a closed porosity at the surface, such as additive manufacturing (AM) or press and sinter methods that achieve high density. Without capsule, the compacted material is exposed to the atmosphere during HIP and it is, therefore possible to adjust the surface properties by carburising or nitriding before gas quenching, similar to conventional case hardening processes. The potential of this process has been evaluated in this work. More than 20 different HIP trials have been performed with variations of atmosphere, time, and temperature. Sinter steels and tool steels have been included in the trials. The materials are characterised and evaluated, and thereafter used to optimise this new process.
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| 18. |
- Shvab, Ruslan, 1985, et al.
(författare)
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Influence Of Cr Alloying Content On The Surface Oxide Composition In Case Of Water-atomized Steel Powder
- 2016
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Ingår i: World Powder Metallurgy 2016 Congress and Exhibition, World PM 2016; Hamburg; Germany; 9 October 2016 through 13 October 2016. - 9781899072477
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Konferensbidrag (refereegranskat)abstract
- Utilization of chromium as an alloying element for water atomized steel powder improves cost and performance efficiency for PM steels. However, presence of Cr puts strict demands on the component manufacturing process due to high oxygen sensitivity of chromium. Hence its effect on surface oxide distribution is of vital importance for the tailoring of the sintering process. A number of experimental steel powders, alloyed with 0 to 4 wt.% of chromium, were prepared by water atomization with subsequent annealing in lab-scale equipment. Powder manufacturing process conditions were kept the same for all the powders. The effect of chromium content in the powder on the surface oxide layer thickness and distribution of particulate oxides features on the powder surface was studied by XPS and HRSEM+EDX.
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| 19. |
- Shvab, Ruslan, 1985, et al.
(författare)
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Manufacturing of Valve Bridge Component Utilizing Lean Alloyed Powders and Vacuum Sintering
- 2018
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Ingår i: Powder Metallurgy Progress. - : Walter de Gruyter GmbH. - 1335-8987 .- 1339-4533. ; 18:1, s. 31-39
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Tidskriftsartikel (refereegranskat)abstract
- Increasing the application area of powder metallurgy (PM) steels for manufacturing of high-performance structural components results in material saving, reduction in energy consumption, etc. In this study, feasibility of the manufacturing of valve bridge component for heavy duty engine utilizing lean alloyed powders and novel vacuum sintering approach, followed by low pressure carburizing, is studied. Three low alloyed steel powders were processed by conventional uniaxial pressing and sintering at 1120 and 1250°C in industrial vacuum furnace. The components were tested under high cycle fatigue testing, simulating real conditions of operation. Fatigue properties did not show significant dependence on the sintering temperature and were comparable to currently used reference cast material. Fracture surfaces of broken samples were analyzed to detect crack initiations and fracture mechanisms as well as quality of sintering. Results showed preferentially ductile failure, well developed sintering necks and clean pore surfaces, indicating good sintering. Tested material in combination with novel vacuum sintering process show to be an attractive alternative for manufacturing of this type of components for heavy duty engine applications.
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| 20. |
- Vattur Sundaram, Maheswaran, et al.
(författare)
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Effect of Density and Processing Conditions on Oxide Transformations and Mechanical Properties in Cr–Mo-Alloyed PM steels
- 2022
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Ingår i: Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science. - : Springer Science and Business Media LLC. - 1073-5623. ; 53:2, s. 640-652
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Tidskriftsartikel (refereegranskat)abstract
- To improve the mechanical properties and performances of water-atomized powder metallurgy steels, it is necessary to enhance the density. Consolidating water-atomized steel powders via conventional pressing and sintering to a relative density level > 95 pct involves processing challenges. Consolidation of gas-atomized powders to full density by hot isostatic pressing (HIP) is an established process route but utilizing water-atomized powders in HIP involves challenges that result in the formation of prior particle boundaries due to higher oxygen content. In this study, the effect of density and processing conditions on the oxide transformations and mechanical properties from conventional press and sintering, and HIP are evaluated. Hence, water-atomized Cr–Mo-alloyed powder is used and consolidated into different density levels between 6.8 and 7.3 g cm−3 by conventional die pressing and sintering. Fully dense material produced through HIP is evaluated not only of mechanical properties but also for microstructural and fractographic analysis. An empirical model based on power law is fitted to the sintered material properties to estimate and predict the properties up to full density at different sintering conditions. A model describing the mechanism of oxide transformation during sintering and HIP is proposed. The challenges when it comes to the HIP of water-atomized powder are addressed and the requirements for successful HIP processing are discussed.
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