Powder Metallurgy High Speed Steel Research Articles

Effect of Heat Treatment on Microstructure and Properties of Powder Metallurgy High-Speed Steel Prepared by Hot Isostatic Pressing

The microstructure and properties of powder metallurgy high-speed steel prepared by hot isostatic pressing with different heat treatments have been studied. The microstructure, phase composition, effect of quenching and tempering parameters, fracture morphology, and mechanical properties of the sample are discussed in detail. The H-HSS sample presents the characteristics of the powder prior to the particle boundary and consists of carbide and ferrite, in which the carbides are fine and evenly dispersed without segregation. The bending strength and hardness of the H-HSS sample are 3112 MPa and 56.3 HRC, respectively. The Q-HSS sample is mainly composed of martensite, residual austenite, and carbides. With the increase in quenching temperature, the grain size of the matrix gradually grows, and the small carbide particles dissolve into the matrix, causing an increase in carbide size and a decrease in quantity. The bending strength and hardness of the Q-HSS sample quenched at 1210 °C achieve the maximum values of 3114 MPa and 68.8 HRC, respectively. After tempering, the martensite is transformed from a quenched lath shape to a needle shape, the residual austenite content decreases, and secondary carbides precipitate from the matrix, resulting in a secondary hardening. The T-HSS sample that is quenched at 1120 °C followed by tempering at 550 °C for 20 min has the best bending strength of 4355 MPa. However, the T-HSS sample that is quenched at 1240 °C followed by tempering at 550 °C for 120 min has a maximum hardness value of 69.5 HRC. The fracture mode of Q-HSS sample is brittle fracture, and the fracture mechanism is cleavage fracture. After tempering, the fracture mechanism of the T-HSS sample presents a transitional fracture mode between the cleavage fracture and micropore aggregation fracture.

Study on Microstructure, Mechanical Properties, Tribological Properties and Service Performance of CrAlN and CrAlBN Coatings Deposited on Powder Metallurgy High-Speed Steel (PM-HSS) and Shaper Cutter by Arc Ion Plating Technique

CrAlN and CrAlBN coatings were prepared on the surface of high-speed steel and shaper cutter by physical vapor deposition (PVD) technique using arc ion source. In the process of coating preparation, the adhesive layers were deposited by low bias voltage (−40 V) and the working layers are deposited by high bias voltage (−130 V). The effects of the addition of B element on the microstructure, hardness, elastic modulus and wear resistance of CrAlBN coating were studied. The results show that B element and its compounds exist in amorphous form in the coating, resulting in lattice distortion of the coating, increase of coating hardness to 37.1 GPa, and decrease of elastic modulus to 406.2 GPa. The addition of B element increases the uniformity of the columnar structure distribution and decreases the width of the columnar structure and grain size. The resistance to elastic deformation and plastic deformation of CrAlBN coating is improved, the wear resistance is improved. The performance of CrAlN and CrAlBN coatings on shaper cutter was studied. It was found that the main failure mode of shaper cutters is boundary wear and the wear mechanism of coatings had changed obviously. CrAlBN coating is mainly due to fatigue induced failure, accompanied by some diffusion wear. The addition of B element makes the CrAlBN coating have excellent resistance to oxidative wear, abrasive wear and diffusion wear during cutting. The results show that the addition of B element can improve the microstructure and mechanical properties of CrAlN coating, and the preparation of CrAlBN coating on the surface of the shaper cutter can significantly improve the service life of the coated shaper cutter, which has significance for the development of the shaper cutter industry.

Effects of sintering temperatures on the microstructure and mechanical properties of S390 powder metallurgy high-speed steel

High-performance complex gear cutters and high-temperature bearings are just some of the applications where high-speed steels (HSSs) shine as a preferred material choice owing to their high hardness and outstanding wear resistance. In this work, the effects of sintering temperature on the microstructure and mechanical properties of S390 HSS prepared via spark plasma sintering (SPS) were investigated with a range of sintering temperatures from 930°C to 1,090°C, a uniaxial pressure of 50 MPa, and a holding time of 5 min. The results demonstrated that the improvements in density, hardness, red hardness, and three-point bending strength were confirmed as the sintering temperature increased from 930°C to 1,090°C. Temperature-induced microstructure evolutions were assessed for their contribution to property enhancement, such as powders with varying dimensions and carbides with diverse morphology and diameter. The specimen with the best comprehensive mechanical properties (67.1 HRC and 1,196.67 MPa) was prepared at 1,050°C via SPS. The wear coefficients decreased as the sintering temperature increased, and the observation results of worn surfaces of test pins confirmed that abrasive wear and oxidation wear dominated the wear experiments. Furthermore, the wear mechanism of dense and porous SPS HSS was illustrated and analyzed in terms of the debris and trapped carbides.

Effect of Different Rolling Passes on Microstructure and Mechanical Properties of M390 Powder Metallurgy High-Speed Steel

Effect of Different Rolling Passes on Microstructure and Mechanical Properties of M390 Powder Metallurgy High-Speed Steel

Quantitative investigation of influence of Al2O3 non-metallic inclusions on bending strength of powder metallurgy highspeed steel

The types, dimensions and quantities of inclusions have been examined to quantitatively investigate their influence on the bending strength and impact toughness of HIPed high-speed steel. MgSiO3 inclusion was found to be less harmful than Al2O3 inclusion in terms of mechanical properties. Additionally, the inclusion of Al2O3 of 0-20 μm under 0.02 vol.% showed a slight influence on the bending strength of certain HSS.

Microstructure and mechanical properties of high carbon M2 powder metallurgy high-speed steel prepared by the carbide addition

ABSTRACT This paper used carbonyl iron powder and carbide powder as raw materials to prepare high carbon M2 powder metallurgy high-speed steel through the cold compaction-sintering method. The evolution of microstructure and properties of the material at different sintering temperatures were emphatically studied. The results show that: The microstructure of the samples is that different types of carbides are uniformly dispersed in the matrix. Since the dissolution of the original carbides is a continuous process, the precipitated carbides are constantly changing with the increase of sintering temperature. Moreover, M2 steel achieves sintering densification near the solidus temperature, the sintering window is expanded to 10–15°C. In the sintering temperature range, the carbides in the samples are fine and uniformly dispersed. The material sintered at 1225°C has the best mechanical properties, with a bending strength of 2754 MPa, and a hardness of 51 HRC. In addition, mechanical properties are greatly improved by heat treatment.

Effects of niobium addition on microstructure and properties of CPM121 powder metallurgy high-speed steel

Effects of niobium addition on microstructure and properties of CPM121 powder metallurgy high-speed steel

A Comparative Study of Various Flow Instability Criteria in Processing Map of the Powder Metallurgy High Speed Steel

The deformation behavior of the 1.15C-4.00Cr-3.00V-6.00W-5.00Mo powder metallurgy high speed steel in hot working processes was investigated by the isothermal compression tests carried out at the temperature of 1000-1150°C and the strain rate of 0.001-1.0s−1 with the height reduction of 60%. The processing maps were constructed, identification of the instability regions and optimization of hot deformation parameters. Different types of instability criteria of PRASAD, MALAS, GEGEL, MURTY and SEMIATIN were compared. It was found that the hot working process of the steel can be carried out safely in the domain of 1040-1130 °C/0.01-1.0 s−1. Furthermore, the temperature and the strain rate had a great effect on microstructures. To obtain a homogeneous microstructure with fine grain, the hot working process should be carried out under the condition of 1050-1100 °C/0.01-0.06 s−1.

Laser surface remelting of powder metallurgy high-speed steel

Laser surface remelting of powder metallurgy high-speed steel

Effect of Vanadium Carbide on Sintering Properties and Microstructure Evolution of Powder High Speed Steel

The effects of different proportions of vanadium carbide(VC) particles instead of V powder on the density, microstructure and properties of powder metallurgy high-speed steel(PM HSS) were studied in this paper. The difference of strengthening phase composition and the mechanism of material properties under different sintering time were analyzed. The testing results show that the bonding state between elemental V and matrix is improved and the sintering densification of HSS is effectively promoted with the increasing proportion of VC particles. When holding time is 90 minutes, a large number of lath-like M2C carbides appear in the sample structure with VC particles. When holding time is extended to 120 minutes, the M2C carbides in the high-speed steel structure decompose completely, and a large number of fine M6C and MC carbides are produced. The mechanical properties of HSS can be improved by increasing the proportion of VC particles. The maximum strength of HSS is up to 2597 MPa when the proportion of VC particles is 150% and the sintering time is 120 minutes. The hardness of HSS is mainly related to density and properties of strengthening phase. The hardness of HSS prepared in this experiment is about 51~52 HRC.

In-situ VN reinforced powder metallurgy M30 steels prepared from water atomized powers via pressureless sintering

ABSTRACTIn this paper, in-situ VN reinforced powder metallurgy high-speed steel was fabricated from water atomised powder via pressureless sintering. During sintering, N would replace C to react with V, resulting in the formation of in-situ VN phase. According to the first-principles calculations, the formation energy of VN was – 9.45 eV while that of VC was – 9.08 eV. The relative density of as-sintered samples reached up to 99%. Homogeneous microstructure and fine reinforced phases were obtained. Ultrafine VN phase (0.5 μm) was uniformly distributed in the matrix. As a result, the mechanical properties were improved. The optimal mechanical performance was obtained in the sample with 1.0 wt.% C addition. The hardness, bend strength and impact energy were 65 HRC, 3011 MPa and 18–22 J, respectively. Besides, the sintering window significantly increased from ∼10 to 30∼50°C.

Complex-shaped high speed steel with high mechanical performance fabricated by gelcasting sintering

Abstract Hot isostatic pressing is the most common method to prepare powder metallurgy high speed steel. However, due to the limitation of the steel capsule, it is still a challenge to directly produce complex-shaped high speed steel. Therefore, a gelcasting sintering process is proposed in this study. Complex-shaped high speed steel parts were prepared. First, fine powders (10 μm) were employed to prepare a gelcasting slurry. Then, the slurry was poured into a silicone mould followed by debonding and pressureless sintering. Nearly full densification was achieved in the gelcasting sintered samples. Homogeneous microstructure was observed with fine carbides (1 – 2 μm) evenly distributed in the matrix. Compared to traditional samples prepared by hot isostatic pressing, the bend strength increased from 2 800 MPa to 3 800 MPa. Additionally, the oxygen content of the sintered samples was lower than 100 ppm.

Cutting performance of deep cryogenic treated and nitrided HSS cutting tool inserts

High speed steel (HSS) is a very important industrial tool material and has been constantly improved for different wear resistance applications and cutting tools, i.e. drills, milling cutters, hobs and for the cutting tools in which the economical cutting speed is too low for choosing the carbide tools. The properties of HSS depend significantly on the parameters of the conducted heat treatment. In this paper, the influence of deep cryogenic treatment in combination with nitriding of metallurgical powder metallurgy HSS on the wear resistance was measured. Additionally, the cutting performance in a single point cutting tool machinability test at the configuration of the dry low-speed turning of steel was investigated. The results showed that deep cryogenic treatment itself, and in combination with nitriding, resulted in the reduction of the wear rate. The results of the single point cutting tool machinability test showed that deep cryogenic treated and nitrided HSS inserts performed worse than the classically heat-treated inserts and deep cryogenic treated HSS inserts exhibited approximately the same flank wear as the nitrided ones.

Diffusion welding of powder metallurgy high speed steel by spark plasma sintering

A diffusion welding of HS 6-7-6-10-0.1LaB6 powder metallurgy high speed steel (PMHSS) is successfully achieved by spark plasma sintering (SPS) for the first time in this research. The effect of welding process in terms of bonding temperature, pressure and time on microstructure evolution and tensile strength of the samples are studied in detail. Results indicate that the temperature plays a vital role on the welding quality. A complete welding can be obtained at 1100℃ within varied ranges of pressure and time. When welded at 1100℃, 30 MPa for 30 min, the tensile strength of the sample after heat treatment reaches 2183.5 MPa, higher than that of the base material, which is further confirmed by the subgrain strengthening effect in SPS from TEM analysis.

Effect of Boride Layer on PM HSS AISI M2 on the Mechanisms Acting in the Transverse Rupture Strength Test

Herein, it was conducted a study in order to examine the main fracture characteristics in the transverse rupture strength test (TRS) of a high speed steel (HSS) AISI M2 produced by powder metallurgy (PM) and with boriding treatment. Four conditions have been studied: as-sintered, borided, normalized and borided + TiN. The TRS tests were conducted in accordance with ASTM B528-12 standard. Density, Vickers hardness and transverse rupture strength properties were evaluated. Fractography was observed by scanning electron microscope (SEM). TRS test in the as-sintered condition had the best performance. The fractography of samples showed very irregular appearance, with interconnected porosity for the matrix of the samples and the boride layer had a smooth surface with low porosity. It was observed on the boride layer, the growth of boride layers inside the pores, filling them, which is a positive factor on the TRS. However, cracks were observed in the FeB/Fe2B interface of boride layer, which embrittle the material and reduce the TRS. In fractography of borided samples, it is observed that two fracture modes occur, mode I and mode II. This should be explained owing to the difference between the elasticity modulus of FeB and Fe2B interface.

In situ synthesis and strengthening of powder metallurgy high speed steel in addition of LaB6

A novel technology which was characterized by the vacuum solid state sintering was developed for powder metallurgy high speed steels production. During sintering, both the WC and Mo2C reacted with Fe and transformed to W and Mo rich M6C carbides which were the common hard phases in high speed steels. Also, a high number of W, Mo and Fe were dissolved in VC, forming the MC carbides. The densification of the material mainly relied on the solubility effect during the M6C and MC carbides formation. By alloying with a 0.1 wt% of LaB6 to the steel, the bending strength and the fracture toughness were improved from 3290 MPa and 25.6 MPam1/2 to 4018 MPa and 29.4 MPam1/2, respectively. The TEM analysis demonstrated three types of reaction products by the LaB6 addition: the amorphous phase, the core-shell structure and the La2O3 phase. The impurity elements such as the Mg, Al, Si, S, Ca, and O were absorbed following the LaB6 addition. Moreover, the deoxidization effect caused by the LaB6 addition promoted the sintering at a high-temperature period which contributed to the bending strength and fracture toughness improvement.

A New Piecewise Dynamic Constitutive Equation of Powder Metallurgy High Speed Steel

In order to optimize the hot working technology of powder metallurgy high speed steel, The hot deformation behavior of powder metallurgy (PM) high speed steel was investigated by Gleeble-1500D simulation at the temperature range of 1000-1150°C, strain rates between 0.001 s-1 and 1.0 s-1 and deformation rate of 60% of the samples. The flow stress under different temperatures and strain rates were analyzed. The results show that the flow stress is influenced strikingly by deformation temperature and strain rate. Both the peak stress and the corresponding strain decrease with the increase of temperature and the decrease of strain rate. Deformation temperature, strain rate and deformation activation energy have a great affect on the microstructure. The value of deformation activation energy is 750.67 kJ/mol. The mathematical model of the strain corresponding to the peak stress was set up. The relationship between the strain corresponding to the peak stress and the strain corresponding to the critical stress can be described as: ec=0.606 ep. The segmental dynamic constitutive equation under different strain was established based on the idea of subsection.

Machinability of Powder Metallurgy Steels Using PcBN Inserts

Primary manufacturing of steels by powder metallurgy (PM) is of increasing interest for a wide range of industrial applications. Especially in automotive parts and tools, PM materials are utilized, as they show advantageous behavior regarding chemical, mechanical and functional properties as well as resource efficiency. Consequently, machining of these materials is an emerging topic for both, industry and science. This paper addresses the machinability of PM steels. Two PM high speed steels (HSS) were characterized and machined varying the machining parameters and edge preparation (PcBN inserts) in longitudinal and orthogonal hard turning. Furthermore, the influence of manganese sulfides (MnS) in the PM material was analyzed by comparing experiments applying alloys with defined content of MnS. Besides tool life and achievable surface roughness, the surface integrity was assessed. The results reveal that the amount and shape of carbides as well as the porosity of the PM steels play an important role in the wear mechanism when machining this kind of materials. As expected, addition of MnS leads to a decrease of cutting forces and allows for significantly higher tool life. The influence of machining parameters and the tool edge geometry is discussed. Based on the results, suitable cutting conditions for machining of PM steels can be derived.

Effect of Annealing on Properties of the TiN & TiAlN Coatings Deposited on Powder Metallurgy High Speed Steel ( S790 )

To improve the mechanical properties of the physical vapor deposition (PVD) coatings deposited on fine-blanking tools and increase the tool life, TiN and TiAlN coatings were deposited on the powder metallurgy high speed steel S790 substrates by Multi-arc ion plating, and then annealed at the temperature of 500°C for one hour in vacuum enviroment. The phase variation, residual stress, morphology, surface microhardness and adhesion strength of coatings were respectively analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), Vickers hardness tester and automatic scratch tester. The preferred orientations in the coatings are not changed after annealing, indicating no disparities in the crystal structure of the coatings. The residual stress of coatings released a little after annealing, however the adhesion strength between the coatings and substrates increased obviously, which indicated that the properties of the TiN and TiAlN coatings deposited on S790 steel were improved.

The Impact of Grinding on Surface Integrity of Powder-Metallurgy High-Speed Steel (S390)

The paper presents an experimental study on the relationship betweenprocess parametersand surface integrity of powder-metallurgy high-speed steel S390 in ultraprecision grinding. The optimal machining parametershave been obtained based on the Taguchi quality design method.The affected layerinduced by ultraprecision grinding has a uniform white layerand an inconspicuous dark layer; there are some carbides in the white layer of some samples; a compressive residual stress field exists on the ground surface. In addition, experiments confirm that lapping can remove the white layer effectively and increase the compressive residual stresses with a growth rate of 65%.The derived results satisfy the real requirements in practice.