AISI 440C Martensitic Stainless Steel Research Articles

Experimental investigation on the performance of AISI 440C martensitic stainless steel against the formation of white etching areas under sliding dynamic loading

ABSTRACT Bearings fail prematurely in transient operating conditions, as a result of flaking that causes changes in subsurface microstructure. In this type of failure, the formation of White Etching Cracks (WECs) is preceded by the formation of White Etching Areas (WEAs). Typically the WEAs are formed due to the dissolution of cementite into the matrix in AISI 52100 bearing steel. This feasibility work investigates the performance of AISI 440C steel against WEAs formation using dynamic load Pin-on-Disc tribometer. Experiments were performed at 4.5 Hz loading frequency, Hertzian pressure 2.02 GPa and sliding velocity of 0.2 ms-1 under the boundary lubrication using Poly Alpha Olefins (PAO). From post-test analysis, it is found that AISI 440C steel trapped more hydrogen than AISI 52100 bearing steel. The comprehensive analysis of materials and lubricants revealed that the performance of AISI 440C stainless steel against WEAs formation is better than that of AISI 52100 bearing steel.

Failure analysis of AISI 440C strand dies used in twin screw extruders during polymer compounding

In view of excellent wear and corrosion resistance, AISI 440C Martensitic Stainless steel finds wide use as Dies in Twin Screw Extruders in Polymer, Food and Pharma applications, especially when either additives, which could be corrosive, are added to aid compounding of polymers or moisture and/or free radicals are present in the processing material. Two AISI 440C Die Plates part of Strand Die Assembly in a φ40 mm size Twin Screw Extruder abruptly cracked during operation in succession disrupting regular production with the second failure occurring after about two years of the Extruder in service. While visual examination of the failed Die Plates showed presence of surface / sub-surface cracks and marks of corrosion, the sectioned Die Plate revealed multiple internal cracks. The hardness survey on the failed Die Plates confirmed values between 30 and 36 HRC, which are about 20–25 HRC lower than the hardness measured in as-supplied condition. Macro-examination of the sectioned Die Plate revealed multiple micro-crack origin locations together with strong evidence of corrosion. The microstructural examination showed carbide network along grain boundaries in a matrix consisting of tempered martensite and revealed intergranular fracture. Fractographic observations using Scanning Electron Microscopy on the cracked Die Plate clearly revealed segregation of fine carbides along crack boundaries. Based on detailed analyses, which included site data collection and investigation, the failure of Die Plates was attributed to Stress Corrosion Cracking. Finally, recommendations were proposed to prevent recurrence of such failures in service.

Microstructure and mechanical properties of low temperature carburizing layer on AISI 440C martensitic stainless steel

In this study, the microstructure and mechanical properties of AISI 440C martensitic stainless steel with low temperature carburizing (LTC) layers were investigated by microscopes, X-ray diffraction (XRD), Vickers indenter and pin-on-disc test device, etc. LTC treatment was conducted at 420 °C for 10–40 h on the quenched-tempered steel samples by pack method. Results indicated that the LTC layers formed on base metal exhibited compact and regular morphology, and carbon-expanded martensite (α′c), Fe3C and Cr23C6 compounds were examined in the LTC layers by XRD analysis. Besides, the layer hardness from 1430 to 1720 HV0.025 with processing time increased, which was approximately three times higher than that of the specimen without LTC treatment. However, as the processing time increased, the adhesion strength of LTC layers deteriorated and the indentation grade decreased from HF1 to HF3. In addition, the wear resistance was significantly improved after the LTC treatment, and the wear rate of the LTC layer decreased by 93.7% in comparison with the untreated condition.

Effect of Deposition Time on Properties of ZrO<sub>2</sub> Coating Prepared Using Electrolytic Method

AISI 440C martensitic stainless steel is one of the most widely studied engineering materials for its tribological properties. It is capable of attaining the best mechanical properties such as high strength and hardness compared to other martensitic grades. Unfortunately, the corrosion resistance of this 440C steel is the lowest among the stainless group, which results in the precipitation of carbide phases. AISI 440C were coated using electrolytic ZrO2 layer deposition method in ZrO(NO3)2 aqueous solution. In order to preserve the high mechanical properties of this steel, various heat treatment processes applied to the coated samples. After drying and annealing, the ZrO2 coated samples were evaluated using SEM, hardness tests and corrosion tests. Some mud-crack had been indicated in all samples. However, it become more homogeneously on the sample which undergoes longer deposition time. This difference resulted in a significant improved on corrosion resistance of ZrO2 coated sample.

Microstructures and properties of friction surfaced coatings in AISI 440C martensitic stainless steel

While martensitic stainless steel AISI 440C is an attractive material for wear protection in many industrial applications, it is difficult to realize satisfactory coatings in this material using conventional weld overlay processes. Friction surfacing, a promising solid-state process, can help in this regard. In the current study, alloy 440C coatings were successfully made on low carbon steel substrates using friction surfacing. Bend and shear tests on coated specimens indicated excellent coating/substrate bonding. Microstructures, corrosion behavior, and wear performance of these coatings were compared with standard heat treated alloy 440C bulk material. While friction surfaced coatings in alloy 440C exhibited superior corrosion resistance to standard heat treated alloy 440C bulk material, their wear resistance was found to be somewhat inferior. Apart from these studies, experiments were conducted to assess the potential of the process for wide area coverage. Studies show that it is possible to achieve well-bonded coatings consisting of multiple overlapping tracks with excellent inter-track bonding. Overall, the current study demonstrates that friction surfacing is a very useful process for producing wear resistant coatings in difficult-to-fusion-deposit materials such as alloy 440C martensitic stainless steel.

Microstructure and sliding wear resistance of an Al–12 wt.% Si/TiC laser clad coating

Metal matrix composite coatings consisting of an Al–12wt.% Si-alloy matrix reinforced with TiC were prepared by laser cladding from mixtures of Al–12wt.% Si alloy and TiC powders. For the processing parameters used (power density 200MW/m2 and interaction time 0.3s), a small proportion of TiC dissolves in the melt, resulting in a microstructure composed of 34vol.% of TiC and 3vol.% of Ti3SiC2 particles dispersed in a matrix consisting of proeutectic α-Al dendrites and α-Al+Si eutectic. The coating material presents a hardness of 165HV and a wear coefficient of 2.24×10−5mm3/(Nm) in ball-on-plate dry sliding wear tests, using quenched and tempered AISI 440C martensitic stainless steel as the counterbody material. Analysis of the worn surfaces showed that the sliding motion of the contacting bodies leads to the formation of a tribolayer consisting of Fe oxides, as well as metallic phases. On the basis of theoretical calculations it is suggested that the primary material removal mechanism involves the propagation of cracks through the thickness of this tribolayer, followed by crack channeling and debonding of tribolayer fragments.

Performance of CBN and PCBN Tools on the Machining of Hard AISI 440C Martensitic Stainless Steel

In this study, flank wear on CBN and PCBN tools due to cutting forces were studied. Turning tests were carried using cutting speeds of 100, 125, 150, 175 and 200 m/min with feed rates of 0.10, 0.20 and 0.30 mm/rev and constant depth of cut. The performances of tools were evaluated based on the flank wear and cutting forces. There is clear relationship between flank wear and cutting forces while turning hard martensitic stainless steel by CBN and PCBN tools. Low cutting forces leads to low flank wear formation and low cutting forces provided good dimensional accuracy of the work material including low surface roughness. Flank wear formation was mostly caused by abrasion and adhesion. The built up edges formed reduced the cutting forces and also causes the heat generated at tool tip and work interface. High cutting forces are identified and this may be due to heat and flank wear combinations. Flank and crater wear on the rake face and hard metal deposition due to diffusion of metals on the cutting tool surface are the damages occurred during process.

Tribological behavior of hafnium diboride thin films

Transition metal diborides and their coatings offer an excellent combination of high hardness, high chemical stability and high thermal conductivity, thus they are excellent candidates for a wide range of tribological applications. In this work, stoichiometric hafnium diboride films were grown by chemical vapor deposition from a single-source, heteroatom-free precursor Hf(BH 4) 4 under conditions that afford highly conformal and smooth films. HfB 2 films of thickness ∼ 0.6 μm deposited on steel substrates were subjected to pin-on-disk wear testing against a counter face disc of AISI 440C martensitic stainless steel. Based on wear measurements, both as-deposited (X-ray amorphous) and annealed (nanocrystalline) samples showed very high wear resistance compared to uncoated samples. For the annealed samples, SEM analysis indicated the formation of a wear resistant composite body in the wear scar, even at depths far exceeding the film thickness, which appears to dramatically improve wear resistance. No mild-to-severe wear transition was observed which indicates that mild wear occurred throughout the wear test. This ensemble of results, when considered in the light of high contact pressures (∼ 700 MPa) used in the study, makes the HfB 2 material potentially attractive for wear-resistant applications.

Effects of laser treatments on cavitation erosion and corrosion of AISI 440C martensitic stainless steel

Laser surface treatments with high and low fluence were employed to induce melting and transformation hardening on 440C. While melting could bring about better improvement in corrosion resistance, transformation hardening was more effective in enhancing the cavitation erosion resistance. Compared with conventional heat treatment, laser treatments resulted in higher corrosion resistance with a wide passive range in NaCl solution, and also in higher cavitation erosion resistance in both deionized water and NaCl solution.

Laser transformation hardening of AISI 440C martensitic stainless steel for higher cavitation erosion resistance

Surface hardening of AISI 440C martensitic stainless steel was achieved by laser transformation hardening (LTH) using a high-power CW Nd:YAG laser. A hardened layer of a few 100 μm thick, composed of martensite, retained austenite and fine carbides was formed. The microstructure and hardness of the laser-treated layer were dependent on the laser processing parameters, with the hardness values reaching the range 600–800 HV. Compared with conventionally heat-treated samples, the laser-treated samples contained more retained austenite and finer carbides due to a higher degree of carbide dissolution. The cavitation erosion resistance of AISI 440C was significantly improved after laser treatment, and was approximately three-fold higher compared with that achieved by conventional heat treatment. The high erosion resistance was attributable to a desirable microstructure, which exhibited a favorable combination of hardness and toughness, and contained fewer weak sites for erosion attack.

Effect of processing conditions on the corrosion performance of laser surface-melted AISI 440C martensitic stainless steel

Laser surface melting of AISI 440C martensitic stainless steel was achieved using a 2.5-kW continuous wave Nd:YAG laser. The pitting corrosion behavior of laser surface-melted specimens processed under different processing conditions in 3.5% NaCl solution at 23 °C was studied by potentiodynamic polarization technique. The corrosion resistance of all laser surface-melted specimens was significantly improved, as evidenced by a shift from active corrosion to passivity, a wide passive range and a low passive current density. The pitting potential of the laser surface-melted specimens P08-440C-25 (laser power=0.8 kW, scanning speed=25 mm/s) and P12-440C-25 (laser power=1.2 kW, scanning speed=25 mm/s) was increased to 260 and 200 mV (SCE), respectively, and was much higher than that of the conventionally heat-treated AISI 440C. The pitting corrosion characteristics of the laser surface-melted specimens were strongly dependent on the processing conditions which resulted in different microstructures. The enhanced corrosion resistance was attributed to the dissolution or refinement of carbide particles and the presence of retained austenite. The amount of carbides in the melt layer, which indirectly determine the Cr content in solid solution and hence, the corrosion resistance, was related to the amount of C remaining in solid solution and to decarburization. The pit morphology of the laser surface-melted specimen was also studied.

X-ray photoelectron spectroscopy characterization of high dose carbon-implanted steel and titanium alloys

A study has been made of the depth dependence of the atomic fraction and chemical bonding states of AISI 440C martensitic stainless steel and Ti–6Al–4V alloy implanted with 75 keV C + at very high doses (above 10 18 ions cm −2), by means of X-ray photoelectron spectroscopy combined with an Ar + sputtering. A Gaussian-like carbon distribution was observed on both materials at the lowest implanted dose. More trapezoidal carbon depth-profiles were found with increasing implanted doses, and a pure carbon layer was observed only on the titanium alloy implanted at the highest dose. The implanted carbon was combined with both base metal and carbon itself to form metallic carbides and graphitic carbon. Furthermore, carbon-enriched carbides were also found by curve fitting the C 1s spectra. The titanium alloy showed a higher carbidic contribution than the steel implanted at the same C + doses. A critical carbon concentrations of about 33 at.% and 23 at.% were measured for the formation of C–C bonds in Ti–6Al–4V and steel samples, respectively. The carbon atoms were bound with metal to form carbidic compounds until these critical concentrations were reached; when this C concentration was exceeded the proportion of C–C bonds increased and resulted in the growth of carbonaceous layers.

Changes in tribological properties of an AISI 440C martensitic stainless steel after ion implantation of carbon at very high doses

Ion implantation of N + or C + has been proven to be a suitable technique for improving tribological properties of steels. In the case of C + implantation at very high doses, amorphization and a carbonaceous layer can be formed on the surface, the latter of which reduces adhesion when like-on-like material contact conditions occur, thereby decreasing surface wear and friction. A study to determine the influence of C + ion implantation at very high doses (exceeding 10 18 ions cm −2) on tribo-mechanical properties of AISI 440C steel is presented in this work. Ball-on-disc wear and friction tests using an AISI 440C steel ball showed a decrease of wear with increasing dose of more than one order of magnitude. A reduction in friction coefficient was also measured, from 1.0 down to 0.4. C 1s spectra from XPS analyses showed the presence of C-C bonds in the ion-implanted samples, suggesting the formation of a graphitic layer on the surface, responsible for the decrease in surface wear and friction after ion implantation.

Wear mechanism maps of 440C martensitic stainless steel

AISI 440C martensitic stainless steel is the material of choice for the high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME). Tests have been done over a range of sliding speeds from 0.5 to 2.0 m s −1, initial hertzian stresses from 0.915 to 3.66 GPa, and bulk temperatures from −184 °C (liquid oxygen temperature) to 760 °C, which cover the variations thought to exist in the HPOTP. Data are presented in the form of contour wear maps to allow a more direct view of the interdependencies of the major tribological variables than can be obtained with wear data presented vs. a single variable. Wear maps are used as a tool to aid in the determination of regions dominated by a given wear mode. Parametric combinations that result in transitions between wear modes are more easily detected with the use of wear maps. Wear maps can simplify design by identifying combinations of speed, load, and bulk temperature that need to be avoided, because of undesirable wear modes.

A low cycle fatigue criterion based on non-linear fracture mechanics: Lundstrom, A. and Tryding, J. Eng. Fract. Mech. 1991 39 (4) 769–781

AISI 440C martensitic stainless steel is the material of choice for the high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME). Tests have been done over a range of sliding speeds from 0.5 to 2.0 m s−1, initial hertzian stresses from 0.915 to 3.66 GPa, and bulk temperatures from −184 °C (liquid oxygen temperature) to 760 °C, which cover the variations thought to exist in the HPOTP. Data are presented in the form of contour wear maps to allow a more direct view of the interdependencies of the major tribological variables than can be obtained with wear data presented vs. a single variable. Wear maps are used as a tool to aid in the determination of regions dominated by a given wear mode. Parametric combinations that result in transitions between wear modes are more easily detected with the use of wear maps. Wear maps can simplify design by identifying combinations of speed, load, and bulk temperature that need to be avoided, because of undesirable wear modes.

A strip model for fatigue crack growth predictions under general load conditions: Wang, G.S. and Blom, A.F. Eng. Fract. Mech. 1991 40 (3) 507–533

AISI 440C martensitic stainless steel is the material of choice for the high pressure oxygen turbopump (HPOTP) of the space shuttle main engine (SSME). Tests have been done over a range of sliding speeds from 0.5 to 2.0 m s−1, initial hertzian stresses from 0.915 to 3.66 GPa, and bulk temperatures from −184 °C (liquid oxygen temperature) to 760 °C, which cover the variations thought to exist in the HPOTP. Data are presented in the form of contour wear maps to allow a more direct view of the interdependencies of the major tribological variables than can be obtained with wear data presented vs. a single variable. Wear maps are used as a tool to aid in the determination of regions dominated by a given wear mode. Parametric combinations that result in transitions between wear modes are more easily detected with the use of wear maps. Wear maps can simplify design by identifying combinations of speed, load, and bulk temperature that need to be avoided, because of undesirable wear modes.

Corrosion behavior of surface films on Boron-implanted high purity iron and stainless steels

Boron (dose, 2 × 10 17 ions cm −2) was implanted into high purity iron, AISI 316 austenitic stainless steel and AISI 440C martensitic stainless steel at 40 keV. The film structure of implanted samples was examined and characterized by contrast and diffraction analyses utilizing transmission electron microscopy. The effect of B + ion implantation on the corrosion behavior was studied using the potentiodynamic polarization technique. Tests were performed in deaerated 1 N H 2SO 4 and 0.1 M NaCl solutions. Scanning electron microscopy was used to examine the morphology of the corroded surfaces after testing.