Low Alloy Powder Research Articles

A comparative study of microstructure and texture evolution in low cost titanium alloy swarf and powder recycled via FAST and HIP

A comparative study of microstructure and texture evolution in low cost titanium alloy swarf and powder recycled via FAST and HIP

On the Use of Metal Sinter Powder in Laser Powder Bed Fusion Processing (PBF-LB/M).

Metal Laser Powder Bed Fusion (PBF-LB/M Powder Bed Fusion, Laser-Based/Metal) offers decisive advantages over conventional manufacturing processes. Complex geometries can be produced that cannot, or only to a limited extent, be manufactured with conventional manufacturing processes. One of the main disadvantages of the process are high investment and operating costs. In order to make the PBF-LB/M process accessible to new research areas, the costs need to be reduced. Therefore, this work investigates whether laser beam sources and motion systems in currently established PBF-LB/M systems can be replaced by more cost-effective components. To reduce the operating costs for PBF-LB/M, the studies are carried out based on previous work with water-atomized, process-foreign sinter powder instead of gas-atomized, spherical PBF-LB/M powders. A cost-efficient, low-alloyed powder is selected (Höganäs HP1) and processed on two different PBF-LB/M machines with a restricted process window using process parameter values that current low-cost machines can achieve. The results show that a multimode fiber laser leads to a more stable process and wider melt pools compared to a single mode fiber laser. In addition, a lower sensitivity of the process with respect to modified process parameters is observed for the multimode laser, resulting in a wider range of stable process windows. A Cartesian motion system (gantry) is suitable for use in PBF-LB/M despite lower scan speeds compared to galvanometer scanners. Beam guidance in the XY-plane offers new possibilities for machine and process design that are not possible with usual scanner systems.

Управление эксплуатационными свойствами порошковых материалов для повышения коррозионной стойкости и износостойкости деталей

Introduction. One of the vibration methods for processing loose finely dispersed mineral raw materials is the sepIntroduction. The quality of powder materials made of rare metals is ensured by chemical-thermal treatment, including diffusion chromosilidation. Chemical and thermal treatment of products intensifies the process of diffusion saturation, reduces the processing time and allows the use of products in aggressive and abrasive environments. Methods and materials of research. Systematization, generalization and analysis of theoretical, laboratory and experimental studies, the basis of which is the modeling of processes. Research results. It was found that when using low-alloyed powder, higher strength and viscosity indices of chromosilicated materials were obtained. It is determined that the mechanical properties of powders processed from molten salts are higher than those of materials from powder filling. It is shown that the treatment increases the corrosion resistance of iron-based powders with an established corrosion rate less than the initial one. Discussion of research results. The rapid formation of an oxide film that protects the metal from corrosion is facilitated by quenching and normalization. Porous chromosilicated layers are destroyed and impair the ability of the material to resist corrosion destruction. The operational properties of chromosilicated powders obtained by hot stamping methods increase when using rational parameters of the technological process in an optimal mode. Conclusion. The article contains new proposals for managing the properties of materials to increase corrosion resistance and wear resistance of children. Conclusions on the article. New developments can be recommended for implementation in the production of rare metals and products made from them. Suggestions. The results of the research can be used both in the modernization of production and in the training of specialists in this field.

Iron Carbon Masteralloy as Sintering Activator for Low Alloy Powder Metallurgy Steels

In real industrial environment there is always a difference between ideal theoretical condition and real production condition which bears the risk of producing defective or low quality parts. Getting closer to this ideal situation requires more effort and investment which tends to increase the production cost. In the P/M production lines, the sintering stage is one of the most critical processes. Maintaining an open continuous sintering furnace in an ideal condition is a challenge, and this issue gets more pronounced when using alloy powder containing oxygen-sensitive elements such as Cr or Mn which provide good hardenability at low cost but on the other hand form stable oxides that weaken the sintering contacts if they are not reduced properly. In the present study, using a carbon master alloy as a sintering enhancer in the sintering process of Cr-Mo alloyed powder compacts has been investigated. For clearly depicting the effect of carbon master alloy addition on carbon dissolution and deoxidation, sintering was done in argon as inert atmosphere to avoid other reducing agents such as H2. The physical and mechanical properties of the sintered specimens were investigated, and thermal chemical analysis by DIL/MS and carbon/oxygen measurements were performed. The experiments showed that adding iron-carbon masteralloys promote the sintering processes such as reduction of oxides and carbon dissolution in the early stages of sintering, resulting in better properties after final sintering.

Solidification Structures in Low-Alloyed Powder Metallurgy Steels Obtained through Permanent Liquid Phase Sintering Using a Master Alloy Containing Boron

Abstract Powder metallurgy (PM) steels containing boron form an attractive group of alloys because of the important densification that can be achieved through permanent liquid phase sintering (LPS). However, upon solidification, such liquid phase is known to form borides or borocarbides. Recent works have shown that some alloying elements have significant interactions with the LPS of PM steels containing boron. More specifically, it is suspected that the concentration of prealloyed molybdenum influences the formation of boride/borocarbide upon cooling at the end of the sintering cycle. Therefore, the main objective of this work is to describe the relationship that exists between the concentration of prealloyed molybdenum and the crystal structure of the boride/borocarbide eutectic component that typically forms in PM steels containing boron. A master alloy made of iron-manganese-nickel-boron-carbon was utilized to introduce boron, thus providing enhanced sintering through LPS. Characterization in optical and scanning electron microscopy combined with electron-backscattered diffraction and energy-dispersive X-ray spectrometry (EDS) revealed that increasing the prealloyed molybdenum content not only increased the volume fraction of liquid phase but also modified the morphology and the nature of the boron-rich eutectic. Changing the prealloyed molybdenum content from 0.5 to 0.85 wt.% transformed the discontinuous M2B boride to a continuous M23(C,B)6 borocarbide phase, causing a drastic decrease in strength despite the higher densification observed at 0.85 wt.% molybdenum. The effect of molybdenum on the LPS process of boron PM steels is undeniable and was found to occur after the initial formation of the liquid phase. Indeed, differential scanning calorimetry revealed no difference in the endothermic melting peaks temperature for both concentration of molybdenum.

Thixotropic properties of multi-functional binder and compaction behaviour of the low alloyed binder-treated powder

ABSTRACTA new multi-functional binder with adhesive and lubricant effect was designed, and the thixotropic properties of the binder components and the resulting binder, the adhesive effect and compaction behaviour of the binder-treated powder were investigated. The results demonstrate that the thixotropic components in the binder are polyethylene wax and microcrystalline wax. With the increase of polyethylene wax content, the critical solid–liquid shear stress of binders decreases gradually. The main lubrication components in the low-pressure and high-pressure stages during the compaction process are found to be polyethylene wax and microcrystalline wax, respectively. The fine metal or graphite additives are effectively bonded on the surface of iron particles and filled in the pits. The green density reaches 7.25 g cm−3 at 600 MPa when the content of polyethylene wax is 30%. From 400 to 750 MPa, the content of polyethylene wax corresponding to the minimum ejection pressure decreases from 20 to 0%.

Manufacturing of Valve Bridge Component Utilizing Lean Alloyed Powders and Vacuum Sintering

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.

Effect of the shell-core-structured particle design on the heating characteristic of nickel-based alloy particle during plasma spraying

In-flight particle temperature is a vital factor controlling the formation of the interface bonding and therefore the overall properties of thermally sprayed coatings. In our previous study, a novel shell-core-structured powder approach was proposed which was designed by cladding low melting point alloy NiCr powders with refractory Mo shell to significantly raise the in-flight particle temperature during plasma spraying to improve the interface bonding within the plasma-sprayed coating. Previous results revealed that the significantly improved interface bonding was obtained for the plasma sprayed NiCr-Mo coating. Therefore, in this study, in order to clarify the effect of Mo-cladding on the temperature evolution of the Ni-based alloy particle, the heating history of the Mo-clad-NiCr particle injected into plasma jet during in-flight process are numerically simulated and further experimentally measured. Effect of particle surface vaporization on the heating characteristic of particle was examined. As a result, both the numerical and experimental results show that through such novel particle design, the elemental vaporization of NiCr core is effectively suppressed and the Ni-based alloy particle is definitely heated up to an ultra-high temperature, 2920K, which is comparable to that of molten Mo particles and is about 500K higher than that of conventional NiCr particle. Consequently, an almost fully-dense NiCrMo coating with excellent interface bonding can be obtained by plasma spraying of this ultra-high temperature Mo-clad-NiCr particle.

The possibility of modifying the elements of the bearing assembly with nanoparticles in order to reduce the friction coefficient

Recent study considers the tribological characteristics of the sintered bushings used in the connecting nodes brake lever system of railway cars. Particular attention is paid sleeves low content of alloying elements. Bushings had been prepared by powder metallurgy route by using low alloyed powders of Fe-Cu-C system. Porosity after sintering was about 20%. Generally, before using material was impregnated by industrial mineral oil in order to improve friction condition.In the recent study we use new lubricating compositions for impregnating in sintered bodies. Such compositions consist of basic mineral oil with addition of 4 wt.% of layered tungsten dichalcogenides (WS2 and WSe2) nanoparticles, which were ultrasonically dispersed. Tungsten disulphide nanoparticles have spherical shape with the diameter of 30-50 nm, and diselenide nanoparticles have a flat shape with the mean dimensions of 5x70 nm. Tribological testing of the product was provided. Sintered bushings impregnated with commercial oil and suspension of nanoparticles were tested in the spinning friction conditions in the couple with bearing steel at the load of 210 N and spinning rate of 200 rpm.The friction test in couple with steel exhibited the value of friction moment to be about 2 times less as compared with commercial oil. The additions of tungsten disulphide nanoparticles also significantly decrease oscillations the friction torque.

From experimental data, the mechanics relationships describing the behaviour of four different low alloyed steel powders during uniaxial cold compaction

ABSTRACTThis work aims at determining the constitutive model of four commercial water atomised low alloyed steel powders during cold compaction. Single-action experiments were performed, obtaining cylindrical specimens with different H/D ratios. The distribution of axial and radial stresses was investigated, and the relationships describing both the radial stress transmission coefficient and the flow stress as functions of the relative density were determined. The radial stress transmission coefficient also confirmed the hypothesised value of Poisson’s coefficient. The friction coefficient between the powder column and the die wall was determined, also highlighting the influence of the H/D ratio. Measuring the axial and radial strains due to spring-back, the axial and radial elastic moduli were determined, as functions of the relative density. The results obtained for the four materials were compared, also highlighting both differences and similarities.

Design and Processing of FGCM Materials for Applications Subjected to Intensive Abrasive Wear

The present work shows the design criteria of FGCM, respectively selection criteria of PM (Powder Metallurgy) matrix, and use of reinforcement particles in correlation with the mechanical stresses resulting in moulds and punches used for steel cold extrusion, powder compaction, sheet metal stamping and series production of parts processed with these tools. Therefore, sintered and repressed state are analysed, and the microstructural and mechanical properties of steel powders used for matrices development, grade High Speed Steels (HSS), AISI M2 and AISI M4, and low alloyed steel powders Ancorsteel 2000 and Ancorsteel 4600 V are defined. Also there are analysed the physical and mechanical properties of the reinforcement particles TiC, WC, Al2O3, B4C, SiC, etc. Are presented the manufacturing methods, the technological parameters for development of functionally graded materials in vertical and horizontal plans, compacting to 500-600 MPa,, sintering temperature to 1050 °C for SiC reinforcement and 1100-1150 °C for matrix reinforced with Al2O3 , repressing to 600 MPa/1100 °C of sintered preforms, heat treatment and wear properties of FGCM materials as Ancorsteel 2000 and Ancorsteel 4600 reinforced with Al2O3 and SiC particles

A New Approach to Heat Treatment of High-Strength Powder Steels

Wear (pin-on-disk) tests of low-alloy powder steels (with 0.5 and 0.65% C) are performed after vacuum sintering combined with hardening. The studied alloying systems are 0.65% C + 1.5% Cr + 0.2% Mo, 0.65% C + 0.9% Ni + 0.9% Mo + 0.2% Mn and 0.5% C + 4% Ni + 1.5% Cu + 0.5% Mo. The wear resistance of the steels after the hardening sintering is an order of magnitude higher than after the conventional sintering. The wear resistance of the steels increases in the following order: pearlitic, pearlitic-bainitic, and martensitic structures. Accordingly, the hardness grows from 98 to 105 HRB.

Relationship between microstructure and mechanical properties of iron–1.8 chromium PM materials

Lean sintered steels can be defined as low alloyed steels with a content of alloying elements <3 wt.-%. Chromium is widely used as an alloying element in low alloyed wrought steels, since it gives good mechanical properties at a low cost. Chromium as alloying element in PM steel is of great interest because of the positive effect on hardenability of PM parts and recyclability of the scrap. However, the use of chromium in low alloyed powder metallurgy steels is very limited. The reason is that chromium has a high affinity to oxygen, which makes the materials sensitive for oxidation during the sintering process.

Mechanical and Acoustical Properties of Bushings Made of Low-Alloyed Materials and Used in Brake Systems of Transport Vehicles

The increasing freight volumes and the speed of transport, as well as increasing demands with regard to safety have made the search and development of new anti-friction materials a topical task. The main requirements to the bearing assemblies include reliability, durability, simplicity and ease of maintenance. The paper considers the features of the manufacture of braking sliding sleeves/ bushings for transport vehicles made from sintered low-alloy powder materials based on Fe-C-Ni with Ni and Mo contents of 0.3%. The paper presents data on the microstructure of the sintered samples of the products and research of some physical and mechanical properties. Surface quality and friction coefficient were evaluated by surface profiling and tribological tests, correspondingly. Particular attention is paid to the use of ultrasonic testing for quality control of the products.

On the tribological behavior of nanoalumina reinforced low alloy sintered steel

Powder metallurgy (PM) technique offers progress of new material processing for applications requiring various combinations of properties. Demanding for applying ceramic materials in tribological concept is increasingly growing over last two decades. Unique characteristic of ceramic materials such as low density, high hardness, low thermal expansion, high corrosion and tribological resistance is the rudimentary reason. In this study, different weight percentage of alumina nanoparticles was added to low alloy powder steel (Astaloy 85Mo) as reinforcement agent. Microstructure and tribological behavior of the metal matrix composite has investigated at dry condition and room temperature for different loads by reciprocating tribometer. Sintered specimens possess homogenous microstructure with bainitic and partial ferrite feature in retained austenite matrix. Outcomes show improvement in wear resistance by increasing of alumina nanoparticles containing 3wt.%, porosity level of 15.38% and micro hardness of 105.4HV which demonstrates the best wear resistance properties. Tribological behavior of PM steel parts is so complex due to existing pores. Not only do surface pores deteriorate the wear resistant as inherent characteristic but also the properties could enhance at optimum porosity level. An important role of surface porosities which have crucial influence on decreasing wear rate is trapping wear debris causes severe wear. Mixed mode of abrasive, adhesive and oxidation mechanisms were distinguishing according to electron image analysis.

Making the most of manganese

Joe Capus looks at a useful alternative to low-alloy powder metallurgy steels and examines how its potential was discussed at PowderMet2011.

Behaviour of Some Unalloyed and Alloyed Sintered Steels at Static and Dynamic Loads

The behaviour of alloyed and unalloyed sintered steels in static and dynamic loading is influenced by their macro and microstructure. The characteristics of the used powder, their chemical composition, the conditions of shaping by pressing, and the parameters of the sintering process are some factors determining the structure of the steels [1, 2]. Under the same technological conditions, sintered materials were produced using iron powder of different particle size or in different powder mixtures for establishing the structure influence on some mechanical properties, The results obtained shows that the sintered materials present a higher sensitivity towards the dynamic and variable loads [2]. In the same time, it was shown that a material made from a fine powder fraction behaves, at mechanical loads, almost in the same way as an elaborated material from the same powder but with a wider particle size distribution or particles size. Using of the different powder mixtures lead to some microstructures with better mechanical properties at the intergranulars necks. Using the copper powder or the low or high alloyed iron powder in a mixture with the basic iron powder determines an improvement of the mechanical properties by changing the materials microstructure. It was found that the addition of high alloyed steel powder has the strongest effect on the fatigue resistance.

High Resistance Porous Pieces Obtained by PM, Reinforced with Metallic Yarns

The paper presents the results of the experiment in the fields of new technologies of obtaining PM reinforced with metallic yarns pieces. This type of high resistance porous pieces are made from a base part from recovered low alloyed steel or iron powder reinforced in the border zone with high alloyed steel yarns. For the reinforcing have been used solid yarns Φ 0,3 mm and mixed yarns Φ 0,45 mm. There have been obtained parallelipipedic samples reinforced with four yarns placed as in fig.1.1. The samples have been pressed at 300-600 MPa pressure. The pressing has been made orthogonal onto the placement direction of the yarns. The compacting has been made in an unidirectional compression mould with section of 7x51mm. The sintering was made at 1200 degree Celsius in an argon medium. The sintered samples have densities of 5,72g/cm3 (pressed at 300MPa) and 6,72 g/cm3 (pressed at 600MPa). There have been made mechanical bending tests. There were obtained bending strengths σi=490…800 MPa. From the things previously presented it can be observed that this type of reinforced with yarns pieces have high bending strength, though they have high porosity (low density).

ANCORSTEEL 2000

Abstract Ancorsteel 2000 is a water atomized low-alloy powder metal containing Ni, Mo, and Mn and is useful in powder metal parts requiring greater hardenability. In the powder production process used to make Ancorsteel, molten steel is atomized into irregular, homogeneous particles which are then annealed to produce uniform, dependable steel powders. Ancorsteel grades are designed for powder metallurgy parts requiring densities exceeding 6.7 g/cm^3 (0.24 lb/in.^3). This datasheet provides information on composition, physical properties, hardness, and tensile properties as well as fracture toughness. It also includes information on powder metal forms. Filing Code: CS-157. Producer or source: Hoeganaes Corporation.

High-strength low-alloy powder steel with a composite structure

The influence of carbon, nanodisperse Ni-Cu alloy, and ZrO2 nanoparticles on the sintering and properties of sprayed iron powder is investigated. The mechanical properties of the new steel with a composite structure exceed by a factor of 2-3 those for the steel of the same composition produced from a mixture of ordinary powder.