M2 Steel Research Articles

Laser Treatment on the Coating Surface Having Been Performed by Means of Plasma Surfacing With Powder Made of M2 Steel

In this study researches were carried out about the impact of pulsed laser irradiation on the surface of M2 steel which had been surfaced beforehand on steel 20 by poweder-pasma surfacing technique. The surface treatment was performed by the single point laser action and by successive imposition of overlapped impulses. During the surfacing the average irradiation power was varied from 15.8 to 21.0 W. The impulse duration in all points was constant and it was 7 msec. In this study it was researched the influence of laser-beam power change on the depth of penetration, changes in the structure and microhardness of treated areas.

Effect of tempering temperature on microstructure and mechanical properties of laser solid formed 300M steel

The microstructure and mechanical properties of laser solid formed (LSFed) 300M steel with tempering treatment was investigated. The microstructure of laser solid formed 300M steel with tempering treatment mainly consisted of the tempered martensite, bainite and a small amount of retained austenite. When the tempering temperature increased from 250 °C to 350 °C, the size of martensite lath and martensite blocks changed little. There are two kinds of tempered martensite. With increase of the tempering temperature, ε-carbide in the general tempered martensite transformed to cementite. In another kind of tempered martensite, ε-carbide were found to be precipitated along specific growth directions, with at least two variants for carbide precipitation. The hardness presented an incomplete linear correlation with the tensile strength and the yield strength for LSFed 300M steel. The hardness in LSFed 300M steel had not shown a significant change with increase of the tempering temperature. The tensile strength and yield strength increased first till the tempering temperature reaches 290 °C–310 °C then decreased with further increasing the tempering temperature. Especially, the strength dramatically decreased when the tempering temperature was above 310 °C. However, the elongation and percentage reduction of area changed little with increase of the tempering temperature. The tensile fracture of LSFed 300M steel with tempering treatment presented a ductile fracture pattern.

MULTIPLE PERFORMANCE CHARACTERISTICS OPTIMIZATION OF HARD TURNING OPERATIONS USING UTILITY BASED-TAGUCHI APPROACH

In order to sustain in the global competitive scenario, the manufacturing industries have beenpracticing the various tools to achieve the high quality products at lower cost. Selection of appropriate cutting conditions is necessary to improve machinabilty of a work piece material. The present work objective is to find out the optimum cutting parameters in turning of hardened AISI M2 steel using cryogenically treated cutting inserts. The Utility concept coupled with Taguchi approach was employed to optimize both surface roughness and power consumption simultaneously. According to Analysis of variance (ANOVA) results, the feed was the major dominant factor followed by the cutting speed on multiple performance characteristics. The necessary optimum conditions for multiple performance characteristics optimization were obtained as cutting speed of 100 m/min, feed 0.04 mm/rev and depth of cut of 0.2 mm.

High-temperature imprinting and superhydrophobicity of micro/nano surface structures on metals using molds fabricated by ultrafast laser ablation

Micro/nano surface structures show great significance in both fundamental research and practical applications. Imprinting technique is widely used to fabricate micro/nano surface structures on polymers at low temperature, but barely implemented on metals. In this paper, femtosecond (fs) laser was used to fabricate micro/nano surface structures on tungsten (W), which served as molds for subsequent solid state imprinting process to replicate the counter structures onto copper (Cu) surface at temperature up to 1000°C. Nano-ripples superimposed on micro-bumps array are fabricated without surface oxidation, and the height of the micro-bumps is adjustable by varying the laser energy input for W molds preparation. The as-prepared Cu surface structures are hydrophobic and turn to superhydrophobic after chemical modification. To demonstrate the feasibility and capability of this technique, similar surface structures were fabricated on A356 aluminum alloy (A356 AA) by liquid state imprinting at 740°C using M2 steel molds prepared by picosecond (ps) laser ablation. This approach combines the advantages of ultrafast laser ablation to fabricate molds with micro/nano surface structures and high-temperature imprinting process to replicate the micro/nano structures onto target metallic surfaces. It opens new possibility for the mass fabrication of functional micro/nano surface structures on metals.

Effect on crystalline structure of AISI M2 steel using tungsten–thorium electrode through MRR, EWR, and surface finish

To investigate on the crystalline structure of AISI M2 steel by using tungsten–thorium electrode in electrical discharge machining (EDM) process was studied. Furthermore, the investigation were carried out for finding the value of material removal rate (MRR), electrode wear rate (EWR) and surface roughness (SR) of tool steel material depending upon three variable input process parameters. On the basis of weight loss, the value of MRR and EWR were calculated at optimized process parameter. Subsequently, surface topography of the processed material were examined through different characterization techniques like scanning electron microscopy (SEM), Optical surface profiler (OSP) and Atomic force microscopy (AFM), respectively. In XRD study, broadening of the peak was observed which confirmed the change in material properties due to the homogeneous dispersion of the particles inside the matrix. Lowest surface roughness and MRR of 0.001208mg/min was obtained. Minimum surface roughness was obtained 1.12μm and 2.18427nm by OSP and AFM study, respectively. Also, minimum EWR was found as 0.013986mg/min.

Tribological performance of few layer graphene on textured M2 steel surfaces

In this study, we propose an easy and effective way to enhance the tribological performance of few layer graphene on M2 steel surfaces. Microgrooves with different area ratios were fabricated on M2 steel surfaces by laser surface texturing method. Subsequently, few layer graphene flakes were dripped on the textured surfaces with graphene-containing ethanol solution. The macro-scale tribological performance of graphene was investigated by ball-on-disk tribometer. The results showed that graphene lubrication with appropriate groove area ratios (35% and 56%) were effective in enhancing the wear resistance compared with that of the bare M2 steel, the improvement was attributed to the effectiveness of wear debris entrapment and the formation of protective carbon layer. Especially with 35% groove area, there was sufficient graphene to reduce the friction, meanwhile, enough support to the high contact stress can be provided as well, demonstrating an obvious improvement in the friction behavior. As a result, low coefficient of friction (COF) around 0.22 can be sustained for 870 sliding cycles.

Effect of Aluminum Addition to Nb-Al-C-N Coatings on AISI M2 Steel Obtained by Thermo-Reactive Deposition Technique

In this study, aluminum-doped (1 and 2 wt.%) and Al-free niobium carbo-nitride coatings were applied to the surface of AISI M2 high speed steel using the process of thermo-reactive deposition technique (TRD) at 1000 ◦C during 1–4 h. The obtained coatings were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis and micro hardness test. Nb-Al-C-N layers were compact and homogeneous. X-ray diffraction analysis has shown that the major phases formed in the coating layer are Nb2CN and NbN. The depth of the coating layer had increased with the treatment time and ranged from 6.65 to 9.05 μm. The measured values of the hardness of the coating layers were ranging between 2136 and 2636 HK0.005.

Corrosion behavior of ultra-high strength steel 300M in different simulated marine environments

Corrosion behavior of 300M in neutral corrosion environments containing NaCl simulated by total immersion (TI), salt spraying (SS) and periodic immersion (PI), was investigated by surface analysis techniques, corrosion weight-loss method, and electrochemical measurements. In total immersion environment, rust on the steel consisted of a porous outer rust layer with main constituent of γ-FeOOH, and an inner rust layer of dense Fe3O4 film with network broad cracks. In salt spraying environment, outer rust with main composition of γ-FeOOH/α-FeOOH/Fe3O4 was compact, and inner rust showed dense Fe3O4 film. Rust formed by periodic immersion exhibited a compact outer rust layer with constituent of α-FeOOH/γ-FeOOH/Fe3O4 and an inner rust layer with composition of α-FeOOH/α-Fe2O3; inner rust showed a ultra-dense film adherent to the steel. The corrosion rate showed a rule of vss(salt spraying)>vti(total immersion)>>vpi(periodic immersion) in 0–240 h, and vss≈vti»vpi in 240–720 h. The rust formed by periodic immersion was dense and compact, with stable electrochemical properties, and had excellent protection on the steel. Humidity and oxygen concentration in all the environments played major roles in rust formation.

FNN model for carbide size of M50 steel during hot deformation

Isothermal compression of M50 steel was carried out on a Gleeble-3500 simulator at the deformation temperatures ranging from 1223 to 1423 K and the strain rates ranging from 10 to 70 s− 1. The relationship between the deformation temperature, strain rate, strain and the carbide size of M50 steel was acquired by simulating the isothermal compression via finite element method, and a fuzzy neural network model for predicting the carbide size during hot deformation was established. The maximum and average difference between the experimental and the predicted carbide size were 9.2 and 4.1% respectively. Applying the present fuzzy neural network model, the effect of the deformation temperature, strain rate and strain on the carbide size of M50 steel during hot deformation was analysed.

Effects of annealing temperatures on the morphological, mechanical, surface chemical bonding, and solar selectivity properties of sputtered TiAlSiN thin films

Quaternary sputtered TiAlSiN coatings were investigated for their high temperature structural stability, surface morphology, mechanical behaviors, surface chemical bonding states, solar absorptance and thermal emittance for possible solar selective surface applications. The TiAlSiN films were synthesized, via unbalanced magnetron sputtered technology, on AISI M2 steel substrate and annealed at 500 °C - 800 °C temperature range. SEM micrographs show nanocomposite-like structure with amorphous grain boundaries. Nanoindentation analyses indicate a decrease of hardness, plastic deformation and constant yield strength for the coatings. XPS analysis show mixed Ti, Al and Si nitride and oxide as main coating components but at 800 °C the top layer of the coatings is clearly composed of only Ti and Al oxides. Synchrotron radiation XRD (SR-XRD) results indicate various Ti, Al and Si nitride and oxide phases, for the above annealing temperature range with a phase change occurring with the Fe component of the substrate. UV–Vis spectroscopy, FTIR spectroscopy studies determined a high solar selectivity, s of 24.6 for the sample annealed at 600 °C. Overall results show good structural and morphological stability of these coatings at temperatures up to 800 °C with a very good solar selectivity for real world applications.

The effect of sliding speed on the wear behavior of pulse electro Co-deposited Ni/MWCNT nanocomposite coatings

In this study, Ni/MWCNT nanocomposite coatings were prepared from a modified Watt׳s type electrolyte by using pulse current (PC) plating technique. The influence of multi walled carbon nanotube (MWCNT) content in the electrolyte on the tribological properties of nanocomposites were tested by using a reciprocating ball-on disk apparatus, sliding against to M50 steel ball (Ø 10mm). Coatings were characterized using Raman spectroscopy, X-ray diffraction (XRD) and scanning electron microscope (SEM) analysis before and after wear testing. Nanocomposite coatings showed wear rate decrease between 1.31 and 1.40 times compared with pure Ni coatings. Friction coefficient decreased from 0.883 for pure Ni coating to 0.419 for the Ni/MWCNT nanocomposite because of graphitization and self lubrication effect of the MWCNTs.

Experimental investigation of transient contact heat transfer between 300M and 5CrNiMo

The contact heat transfer between 300M steel and 5CrNiMo die steel has an important influence on the hot forging process of 300M steel. The accurate thermal contact conductance data are needed for the optimal design and numerical simulation of the hot forging process of 300M steel. Consequently, in this study, a set of new experimental apparatus and relevant procedure were developed to measure the thermal contact conductance at the interface between 300M and 5CrNiMo based on the transient method. The effects of the initial temperature of the 300M specimen, the interfacial pressure, the oxide layer and the graphite lubricant on the thermal contact conductance were evaluated.

Analysis of a New High-Toughness Ultra-high-Strength Martensitic Steel by Transmission Electron Microscopy and Atom Probe Tomography

The microstructure of a new martensitic high-strength steel (Fe-0.40C-3.81Ni-1.31Cr-1.50Si-0.75Mn-0.52Mo-0.51Cu-0.30V) with high fracture toughness is characterized by transmission electron microscopy and atom probe tomography (APT). MC, M6C, and M23C6 precipitates form inside the martensitic lath matrix. The fracture toughness is insensitive to the dissolution of M23C6 precipitates at austenitizing temperatures above 1164 K (891 °C). APT reveals that solute segregation at the prior austenite grain boundaries (PAGB) is not uniform, with C, Mo, Si, Ni, and/or P enrichment varying at different areas of the PAGB. Si depletion is detected in the same area as the highest C enrichment. Carbon also segregates at lath boundaries. Segregation of C indicates the presence of retained austenite films at both PAGB and lath boundaries. Regions enriched in C up to 10 pct were found within the laths; however, no regions were enriched to the level expected of cementite or e-carbide. The observed C distribution and high fracture toughness indicates that the tempering behavior is significantly different than that observed in 300M steel. The effect of Si, Ni, and Cu on the formation and stabilization of the regions of C enrichment and retained austenite require further study, as it may be key to the increased toughness.

Effect of change in temperature on the tribological performance of micro surface textured DLC coating

Abstract

Influence of Residual Stress and Temperature on the Cyclic Hardening Response of M50 High-Strength Bearing Steel Subjected to Rolling Contact Fatigue

Microstructural and mechanical characterization investigations on three variants of a through-hardened M50 bearing steel are presented to compare and contrast their performances under rolling contact fatigue (RCF) loading. Baseline (BL) variant of M50 steel bearing balls is subjected to: (i) a surface nitriding treatment and (ii) a surface mechanical processing treatment, to obtain distinct microstructures and mechanical properties. These balls are subjected to RCF loading for several hundred million cycles at two different test temperatures, and the subsequent changes in subsurface hardness and compressive stress–strain response are measured. It was found that the RCF-affected subsurface regions grow larger in size at higher temperature. Micro-indentation hardness measurements within the RCF-affected regions revealed an increase in hardness in all the three variants. The size of the RCF-affected region and intensity of hardening were the largest in the BL material and smallest in the mechanically processed (MP) material. Based on Goodman's diagram, it is shown that the compressive residual stress reduces the effective fully reversed alternating stress amplitude and thereby retards the initiation and evolution of subsurface plasticity within the material during RCF loading. It is quantitatively shown that high material hardness and compressive residual stress are greatly beneficial for enhancing the RCF life of bearings.

Research on the High Temperature Constitutive Model of 300M Ultrahigh Strength Steel

300M ultrahigh strength steel has good mechanical properties. It has been widely used in the force bearing components of aircraft. In this paper, By using Gleeble1-500D thermal simulator, we studied the change regularity of stress-strain curve of 300M steel using hot compression deformation when temperature is from 800°C to1100°C, strain rate is from 0.001 S-1to 1 S-1 and the strain is 0.7.The experimental results showed that when the strain rate is constant, the flow stress and the peak stress decrease with the increase of deformation temperature. When the deformation temperature is constant, the flow stress and peak stress increase with the increase of strain rate. From the test, we got the true stress-strain curve, calculated the thermal deformation constants such as the deformation activation energy of 300M ultrahigh strength steel. Eventually, we built the thermal deformation constitutive model in hyperbolic sine form of 300M steel.

Comparison of Mechanical and Microstructural Characteristics in Maraging 300 Steel Welded by PAW and GTAW Processes Submitted to Repair

Maraging steels are a special class of ultrahigh-strength steels which presents a combination of high mechanical strength, excellent toughness, high temperature strength and corrosion resistance. The joint of sheets/plates by welding processes are fundamental for aeronautical and industrial products in addition Brazil has been developing technologies in welding ultrahigh-strength steels such as AISI 4340ESR and SAE 300M steels for its domestic space launch program and has currently decided for the replacement of these steels by Maraging 300 steel in some projects. In this work, we studied the welding process of the Maraging 300 steel for two different routes: Tungsten Inert Gas (TIG or GTAW) and Plasma Arc Welding (PAW). Filler additions were used for both processes. Procedure after any welding demands non destructive testing and sometimes non approved defects considering the usage of the product require for welding repair. Verification of the effects of this operation was made through a simulation of a welding repair for both types of welding. Specimens were submitted to heat treatment consisting of a solution annealing and aging and their microstructures were examined. The microhardness measurements were made on samples with and without repair characterized the fusion and heat affected zones. Specimens were submitted to tensile testing and the fractured surfaces were examined by a scanning electron microscope. Results of microstructure exam revealed the presence of austenite (γ) in FZ (Fusion Zone). After the welding repair simulation, a new different colored zone appeared in the HAZ (Heat Affected Zone) for both processes due to reheating of the sheet provided by the repair process. In the HAZ near FZ an important grain growth due to the heating occurred. Also, close FZ that was submitted to new heating due to repair it was noted an apparent growing of grain size relative to original grain size. The microhardness measurements showed that there is a reduction in hardness in the FZ and the region immediately (fusion line) compared to base material values. After the aging heat treatment a recovery of hardness values took place in these regions but the values themselves remain smaller than the base material. It was observed an increase of values of the microhardness in dark regions in the HAZ provoked by a phenomenon of aging locally due to the dissipation of the heat of the welding process and posterior repair. After aging, those differences disappeared. It was observed that there was not a large difference between the yield and strength limits considering both processes of welding, as well as between both situations after repair. It could be seen that the rupture began in the region near FZ and followed in the direction of the weld bead. The analysis of the fracture surfaces showed that this happened by ductile way, forming dimples.

The structure and toughness of TiN coatings prepared by modulated pulsed power magnetron sputtering

Titanium nitride (TiN) coatings were prepared on different substrates (Si wafer, M2 steel, glass) by modulated pulsed power (MPP) sputtering and continuous dc magnetron sputtering (dcMS). The structure and properties were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), nanoindentation and the Vickers indentation test. It was found that the structure was transformed from the columnar growth to the branched growth as the peak target current density (Id) increased to 0.4 A/cm2. The results of plasticity index δH and microindentation crack showed the toughness was improved. MPP TiN coating could withstand the maximum load of 4.9 N when microindentation crack was first discovered at 0.4 A/cm2 while 0.49 N at 0.02 A/cm2 in dcMS condition. This indicated that the high ion flux bombardment of the MPP plasma could be applied to change the structure and toughen TiN coatings.

Bending properties of functionally graded 300M steels

The bending behavior of compositionally-graded martensitic steel was investigated in partially decarburized sheets of alloy 300M. The best combination of strength and bendability was obtained when the thickness of the inner hard core was reduced to one third of the sheet thickness. The improved bending behavior of the compositionally-graded sheet is attributed to (a) the suppression of crack propagation by introducing a more ductile phase at the surface and (b) the spreading of plasticity along the circumferential direction as a result of the presence of a yield stress gradient in the thickness direction. The bendability of the graded material was limited by the initiation and rapid propagation of fracture within the hard core of the sheet. Unlike traditional materials in which the springback angle increases remarkably with increasing yield strength, the compositionally graded material had a small springback angle which is comparable to that of steels having a low yield stress similar to that of the soft decarburized surface layer.

Comparative research on dry sliding wear of hot-dip aluminized and uncoated AISI H13 steel

In order to improve the elevated-temperature wear resistance of steels, an aluminized coating consisting of FeAl and Fe3Al was prepared on AISI H13 steel by hot-dip aluminizing and subsequently high-temperature diffusion. Dry sliding wear tests were conducted for the aluminized and uncoated AISI H13 steel against AISI M2 steel at room temperature and 600°C, respectively. Compared with the uncoated H13 steel, the aluminized steel possessed excellent elevated-temperature wear resistance, in spite of worse room-temperature wear performance. As the load increased, the wear rate of the aluminized steel rapidly increased at room temperature, but maintained extraordinarily low values at 600°C. On the contrary, with an increase of load, the wear rate of H13 steel marginally increased at room temperature, but rapidly increased at 600°C. The aluminized steel seemed to be suitable to the applications involving elevated-temperature sliding. Interestingly, the excellent elevated-temperature wear performance of the aluminized steel was noticed to be attributed to the protection of the thin tribo-oxide layer with a strong support from high thermal-strength intermetallic compound.