M2 Steel Research Articles

Metal matrix composites for fabricating tooling

The objective of this work is to investigate the fabrication, microstructures and, properties of metal matrix composites (MMCs) net-shaped using a four-step hybrid manufacturing method. The manufacturing method consisted of soft tooling fabrication, slurry casting, debinding-sintering followed by metal infiltration. Firstly, silicone rubber molds were fabricated. Subsequently, WC-Co pellets and stainless steel powders were mixed with polymer-based binders and cast into these rubber molds. After solidification, the parts were removed from the rubber molds, and placed in a furnace for debinding and sintering. Finally, sintered parts were infiltrated with bronze and the ensuing microstructures and properties were evaluated. The dimensional changes and mechanical properties of these MMCs as a function of amount of infiltrant were also examined. The results showed that the wear resistance of the MMC parts was comparable to M2 and D2 steels. Demonstrations of the process for net-shaping MMCs were conducted by fabricating wear-resistant tooling. The implications for fabricating MMCs by directly 3D printing rubber molds soft tooling are presented.

Control of flow lines during the forging process of bearing outer rings with a deviated groove

In this paper, the evolution of flow lines during the forging of bearing rings was investigated. The formation mechanisms of flow-line defects were revealed by a finite element method (FEM) simulation of the entire forging process. To avoid the flow-line disorder caused by the bearing ring manufacturing method, two hot forging processes were employed to optimize the flow-line distribution of an M50 steel bearing ring with a deviated groove. The simulation and experimental results show that the punching die and the location of the punching recess had a significant effect on the flow-line formation. The V-shaped punching pin and punching recess setting at the bottom of the billet resolved the flow-line disorder caused by the punching process. Finally, a bearing outer ring with a reasonable flow-line distribution was obtained. Furthermore, the improved hot forging process reduced the average grain size and improved the M2C carbide-aggregation phenomenon. Given the direction of the flow lines, the bearing ring exhibited mechanical anisotropy in the tensile direction.

Galvanic corrosion of the anodized 7050 aluminum alloy coupled with the low hydrogen embrittlement Cd[sbnd]Ti plated 300M steel in an industrial-marine atmospheric environment

The industrial-marine atmospheric corrosion behavior and mechanism of anodized 7050 Al alloy coupled with low hydrogen embrittlement CdTi (LHE CdTi) plated 300M steel were investigated by means of morphology observations, corrosion product analysis and mechanical property testing. The results showed that the CdTi coating reduced the potential difference between the cathode and the anode, and greatly weakened the galvanic corrosion. Therefore, the self-corrosion of anodized 7050 Al and LHE CdTi plated 300M steel dominated the corrosion process. The pitting and intergranular corrosion (IGC) of the anodized Al were severe, and significantly reduced the strength and elongation. The corrosion products composed of AlOOH, Al(OH)3 and Al2(SO4)3 distributed non-uniformly on the surface. The high concentration of Cl− in the industrial-marine atmosphere destructed the anodized films and induced the pitting corrosion of the Al alloy. Due to the pitting and the micro-galvanic corrosion at the grain boundary, the IGC initiated and propagated. In addition, the sulfide dissolved into the thin electrolyte film and aggravated the pitting and IGC. For the LHE CdTi plated steel, the sacrificial CdTi coating was preferentially corroded, and the further corrosion was inhibited due to the corroded surface composed of cadmium hydroxides, chlorides and sulfates.

Rolling Contact Performance of a Ti-Containing MoS2 Coating Operating Under Ambient, Vacuum, and Oil-Lubricated Conditions

Solid lubricant molybdenum disulfide (MoS2) coatings have been frequently used to lubricate mechanisms operating in environments where oil and grease lubrication are ineffective. This work evaluated the rolling contact performance of a Titanium-containing MoS2 coating under humid ambient, vacuum, and oil-lubricated conditions. Weibull analyses of L50 lifetimes of AISI 52100 steel balls coated with a Ti-MoS2 coating paired with uncoated M50 steel rods were determined to be 3.7, 14.5, and 158.6 million cycles in ambient, vacuum, and oil-lubricated environments, respectively. In the ambient and vacuum tests, failures were determined to be associated with the onset of abrasive wear rather than fatigue or spalling. The L50 lifetimes of tests performed in those environments were found to depend upon the wear rate of the coatings on the balls. That is, the Ti-MoS2 functioned as a barrier to the onset of abrasive wear between the steel alloys until the coating was sufficiently worn away. Under oil-lubricated (boundary lubrication) conditions, L50 was found to depend on the durability and composition of tribofilms formed in-situ on the surfaces of the uncoated M50 rods. The tribofilms were comprised of mixtures of MoS2 crystallites and amorphous hydrocarbon (a-C:H). The crystalline MoS2 in the tribofilm originated from the amorphous Ti-MoS2 coating and likely underwent a thermodynamic phase transition as a result of the applied Hertz stress and frictional heating in the contact. The a-C:H in the tribofilm probably originated from a catalytic scission of the polyalphaolefin (PAO) molecules caused by the d-band character of the Mo or Ti in the coating. Overall, the Ti-MoS2-coated balls were effective at extending the operational lifetimes of M50 rods under ambient, vacuum, and oil-lubricated conditions by an order of magnitude.

In-situ observations and modeling of metadynamic recrystallization in 300M steel

The metadynamic recrystallization (MDRX) behaviors and microstructure evolution of 300 M steel are studied by hot compression experiments and high temperature laser scanning confocal microscopy (HTLSCM) experiments. The effects of insulation temperature, pre-strain rate and holding time on the MDRX behaviors are discussed in detail. Based on the statistical results of the microstructure evolution, the MDRX kinetics model and recrystallization (RX) grain size model of 300 M steel are established, respectively. It can be confirmed from the in-situ observations that strain-induced boundary migration mechanism and curvature-driven grain boundary migration mechanism are the main MDRX mechanisms of 300 M steel. The MDRX develops rapidly under the high temperature or low pre-strain rate. The insulation temperature has a more important effect on the MDRX rate. The RX grain size increases with the increased insulation temperature, pre-strain rate and holding time. Compared to the pre-strain rate, the effects of insulation temperature on the maximum MDRX fraction and RX grain size are negligible. Comparisons between the experimental and predicted results verify that the proposed MDRX kinetics models and RX grain size model can quantificationally reveal the MDRX behaviors of 300 M steel well.

The formation of heterogeneous wear-resistant coatings by the additive technology method

The microstructure, hardness property and wear resistance coatings of WC, Ni-Cr and Fe powders deposited by laser cladding at varying processing parameters were investigated. The results of the present study revealed the prospects of multilayer cladding of R6M5 high-speed tool steel (analogy of M2 steel) onto low-alloy steel with the use of a laser beam. Controlling thermal cycles of laser cladding, it is possible to obtain a clad coating made of high-speed steel having the structure of high-alloy austenite martensite mixture with disperse inclusions of carbides up to 10 mm thick, i.e., it is actually possible to create bimetal structures. The wear resistance of the laser-clad self-fluxing PG-10N-01 (Ni-Cr-B-Si-C) alloy increases by a factor of 5 due to additional hardening by cast tungsten carbide with spherical particles. As a result, it becomes higher than the wear resistance of high-speed steel by more than a factor of 3.

Characterization of Friction Surfaced Deposits on Low Carbon Steel

Surfacing With Friction Is A Process Derived From Friction Welding With Advantages Over Commercial Fusion Welding Processes, With Solid Phase Bonding. Here An Experiment Is Conducted To Produce Friction Surface Coating For Three Different Materials Like Aluminum And Stainless Steel And Tool Steel M2 Coating On Low Carbon Steel By Friction Surfacing. The Aim Of This Work Deposition Of Different Materials Is To Identify The Feasibility Of Friction Surfacing And Industrial Applications, Testing Of Deposits For Quality Evaluation Are Carried Out.

Effect of shot peening on short crack propagation in 300M steel

The short crack growth behaviour of high strength martensitic 300M steel was studied for as-machined, polished and 2 peening conditions subjected to axial fatigue at 2 stress amplitudes. It was observed that prior austenite grain boundaries acted as barriers to short crack propagation in peened specimens within the peening induced compressive residual stress layer, causing crack decelerations upto 6 grains. Using the da/dN-ΔK trend of the short cracks, fatigue lives of the peened specimens were predicted at both the stress amplitudes. These analytical predictions (which reflect the effect of microstructure and compressive residual stresses) were within 15% of the experimental fatigue lives.

A new M50 matrix composite sintered with a hybrid Sns/Zno nanoscale solid lubricants: an experimental investigation

To improve the tribological behavior of AISI M50 steel (M), ZnO and SnS nanoscale solid lubricants were added to M50 matrix and sintered using spark plasma sintering technique (SPS) to fabricate two self-lubricating composites: M50 + SnS (MS) and M50 + ZnO + SnS (MZS). Friction tests were performed on a pin-on-disk tribometer using a silicon nitride ceramic under different loads (3, 6, 9, and 12 N) and different speeds (0.2, 0.4, 0.6, and 0.8 m s−1) to figure out the effects of theses parameters on the tribological performance of the developed composites. FESEM, EPMA, EDS, and XRD tests were performed to analyze the worn surface morphology and to understand the friction-reduction and anti-wear mechanisms of the developed composites. Wear and dry friction properties of MS and MZS were found to be superior at high loads and sliding speeds. Applied loads and sliding speeds change widely the wear mechanisms of M50 steel. Excellent tribological characteristics of the developed composites were attributed to the synergistic effects of ZnO-SnS and the created lubricious oxides, carbonates, and molybdenites on wear track surfaces.

Deciphering deformation mechanisms of hierarchical dual-phase CrCoNi coatings

Hierarchical CrCoNi medium entropy alloy (MEA) thin films with a dual-phase face-centred cubic (FCC) and hexagonal closed-packed (HCP) nanostructure were prepared on M2 steel substrates by closed field unbalanced magnetron sputtering. Nanoindentation tests show an ultra-high hardness of 9.5 GPa, attributable to large amounts of innate planar defects (i.e., growth twins and stacking faults) impeding dislocation motion in the coatings. A deep analysis of undeformed and post-mortem samples reveals grain refinement as the dominant deformation mechanism in FCC dominated regions, while phase transformation and shear banding played major roles in regions occupied by HCP phase. The grain refinement was facilitated by twin/matrix lamellae, with dislocations piling up and arranging into interconnecting grain boundaries. The shear banding was accelerated by innate planar defects in the HCP phase due to a lack of slip systems. Of particular interest is the observation of HCP → FCC phase transformation, which was catalysed by deformation-induced grain reorientation with innate stacking faults acting as embryos to grow the FCC phase. The results of this work suggest that multiple deformation pathways could be activated in CrCoNi coatings with assistance of growth defects, thereby imparting these technically important coatings appreciable ductility.

On origin of delta eutectoid carbide in M2 high-speed steel and its behaviour at high temperature

Abstract Delta eutectoid can affect mechanical properties of high-speed steels. Nevertheless, the morphology and the origin of the carbide formed in delta eutectoid, as well as its microstructural changes under the effect of high temperatures, have not been completely investigated till now. To overcome it, the morphology and origin of the carbide in the delta eutectoid of M2 steel were thoroughly examined. The results showed that both M2C and M6C carbides could simultaneously form delta eutectoid. During annealing at 1200 °C, M2C decomposed into the mixture of M6C and V-rich carbides.

Boriding Kinetics of FeB and Fe2B Layers on AISI M2 Steel by the Integral Diffusion Model

Boriding Kinetics of FeB and Fe2B Layers on AISI M2 Steel by the Integral Diffusion Model

Hot Workability of 300M Steel Investigated by In Situ and Ex Situ Compression Tests

In this work, hot compression experiments of 300M steel were performed at 900–1150 °C and 0.01–10 s−1. The relation of flow stress and microstructure evolution was analyzed. The intriguing finding was that at a lower strain rate (0.01 s−1), the flow stress curves were single-peaked, while at a higher strain rate (10 s−1), no peak occurred. Metallographic observation results revealed the phenomenon was because dynamic recrystallization was more complete at a lower strain rate. In situ compression tests were carried out to compare with the results by ex situ compression tests. Hot working maps representing the influences of strains, strain rates, and temperatures were established. It was found that the power dissipation coefficient was not only related to the recrystallized grain size but was also related to the volume fraction of recrystallized grains. The optimal hot working parameters were suggested. This work provides comprehensive understanding of the hot workability of 300M steel in thermal compression.

High Temperature Wear Resistance of Cobalt-Based Cladding Layer Surfacing on H13 Steel

In order to improve the wear resistance of H13 steel, a layer of cobalt-based cladding layer was deposited on the surface of H13 steel by plasma transfer arc welding technology. High-temperature wear test was carried out on H13 steel and cladding layer under 300N loading force, and the two materials were ground at different temperatures with 300M steel. The experimental results show that under 300N loading force, the wear resistance of the cladding layer and H13 steel decreases first and then increases with the increase of temperature, which is related to the softening and oxidation of the material. At 350°C,the material softens and the oxide layer fails to entirely cover the wear surface, so the wear resistance of the cladding layer and H13 steel is lowered. At 500°C and 650°C, the wear surface is covered by a dense oxide layer, which protects the surface of the material from direct wear. The higher the temperature is, the thicker the oxide layer is and the better the protection effect is. At various experimental temperature, the wear resistance of the cladding layer is better than that of H13 steel. The surfacing of a cobalt-based cladding layer on the surface of H13 can improve the wear resistance of H13 steel.

A Microstructure Obtained on AISI 1018 and AISI M2 Steel by Powder Paste Pack Boriding Process

A Microstructure Obtained on AISI 1018 and AISI M2 Steel by Powder Paste Pack Boriding Process

TiN and Boride Layers Obtained by Dehydrated Paste-Pack Boriding and PVD Treatments Formed on AISI M2 Steel

TiN and Boride Layers Obtained by Dehydrated Paste-Pack Boriding and PVD Treatments Formed on AISI M2 Steel

High Temperature Plastic Deformation Behavior of As-Cast 300M Steel Based on Friction Correction

Hot deformation behavior of as-cast 300M steel was investigated in the temperature range of 850-1200°C and strain rate range of 0.01-10 s-1 using Gleeble-3800 thermo-mechanical simulator. Based on the true stress-strain curves corrected for friction, flow stress behavior and deformation mechanism were analyzed, and the constitutive model of as-cast 300M steel was established based on the Arrhenius model and Zener-Hollomon parameter (Z). The microstructure after deformation was observed by Olympus GX51 microscope. The experimental results show that the flow stress of as-cast 300M steel decrease with the increase of deformation temperature and the decline of strain rate. The dynamic recrystallization is more likely to occur at higher temperatures and lower strain rates. By regression analysis, the hot deformation activation energy (Q) of the as-cast 300M steel was calculated to be 360.332 kJ/mol. Microstructure evolution is greatly affected by deformation temperature and strain rate. The dynamic recrystallized grain size increases with the enhancement of deformation temperature and the decrease of strain rate.

Effect of microstructure on the Charpy impact properties of directed energy deposition 300M steel

Direct manufacturing techniques, such as directed energy deposition (DED), are able to produce complex components efficiently. In this study, microstructure evolution and impact toughness of DED 300M ultra-high strength steel are investigated. The results show that the microstructure of the as-deposited DED 300M ultra-high strength steel is mainly composed of martensite and some blocky bainite. The micro-segregation of elements is observed within the interdendritic area. After heat treatment, the microstructure becomes uniform and consists of martensite and lower bainite. The impact toughness of the as-deposited DED 300M ultra-high strength steel is 9 J/cm2, while it is significantly increased to 25 J/cm2 after heat treatment. Furthermore, it is observed that the fracture mode of the as-deposited sample is quasi-cleavage fracture. During the process of propagation, the main cracks would go across the martensite packet and deflect in the another one, and secondary cracks also deflected in the high-angle grain boundaries. By contrast, the fracture mode of heat-treated DED 300 M steel is ductile fracture.

Lubricity of Low-Viscosity Aviation Fuel JP-10 and Tribological Behaviors of Silver (Ag) Films in JP-10

To increase the thrust-to-weight ratio and reliability of gas turbine engines, conventional oil-lubricated bearings are desired to be replaced by fuel-lubricated bearings in fuel pumps. The present study aimed to examine the lubricity of low-viscosity aviation fuel JP-10 with ball-on-disc (Si3N4 ball/M50 steel disc) friction tests at ambient temperature and evaluate the tribological performance of self-lubricious silver (Ag) films while sliding in JP-10 against an Si3N4 ball. Four hundred–nanometer-thick Ag film was deposited on M50 steel by magnetron sputtering and high-current pulsed electron beam (HCPEB) was employed to alloy the as-deposited Ag film. Coefficients of friction (COFs) and wear topographies indicate that JP-10 had decent boundary and hydrodynamic lubrication performance, which was significantly better than that of deionized water but far weaker than that of professional lubricant. In JP-10, the counterpart almost immediately tore the as-deposited Ag film down from the M50 steel substrate, but the wear of the exposed steel surface was slight compared to that of bare M50 steel. Transferred Ag on the friction interface was probably responsible for the significant wear reduction but cannot effectively decrease the COF. The HCPEB-treated Ag film exhibited low friction (0.12) and effective wear protection in JP-10, but it can only function in a relatively short time in low-load conditions because of rapid wear. After wear-out, the COF rapidly rose higher than 0.2. The present work suggests that both types of Ag films are potential tribological surface modification approaches to raceways of fuel pump hybrid bearings for short-range applications.

The effect of ultrasonic nanocrystal surface modification on low temperature nitriding of ultra-high strength steel

In this research, a surface plastic deformation layer was induced on 300M ultra-high strength steel using ultrasonic nanocrystal surface modification (UNSM). The UNSM-treated and control specimens were then nitrided at 450 °C for 6 h. After gas nitriding, the microstructure, corrosion and wear resistance of 300M steel with and without UNSM pre-treatment were investigated. After nitriding, the UNSM-treated specimens generated a dense surface nitride layer that was thicker than that of the control specimens. The high defect density and refined lath martensite induced by UNSM were found to accelerate the nitrogen diffusion and efficiency. X-ray diffraction patterns revealed that α-Fe phase occupied the largest proportion in the nitriding layer of specimens without UNSM pre-treatment. However due to the higher nitriding efficiency, the main phase of UNSM-treated specimens after nitriding was found to be ε-Fe2-3N. Compared with the specimens without pre-treatment, UNSM-treated specimens exhibited higher surface hardness as well as higher corrosion and wear resistance after nitriding.