PH Stainless Steel Research Articles

The Scratch Resistance of a Plasma-Assisted DUPLEX-Treated 17-4 Precipitation-Hardened Stainless Steel Additively Manufactured by Laser Powder Bed Fusion

The Scratch Resistance of a Plasma-Assisted DUPLEX-Treated 17-4 Precipitation-Hardened Stainless Steel Additively Manufactured by Laser Powder Bed Fusion

Strengthening and precipitation hardening mechanisms of surface-mechanically treated 17-4PH stainless steel

Achieving ultra-high strength without sacrificing too much ductility is the focus of attention in nanostructured materials. Here, the strengthening mechanism and property enhancement of surface-mechanically treated 17-4PH stainless steel (SS17-4PH) were investigated. Our findings show that a grain refinement and elongated lath-like martensitic grain (~ 50 nm thick) could be produced after surface treatment. The grain size remains in the nanoscale, and random crystallographic orientations with the presence of nanocrystallites characterize the nanocrystalline grains formed on the treated sample. This contributes to the property enhancement with a yield strength of about 901 MPa and a reduced elongation to failure of about 17%. The atom probe tomography (APT) characterization unveiled the emergence of high-density precipitate (Cu-rich) at the material surface, with a number density of about 2.6255 × 1024 m−3 and an average radius of 2.22 nm. Besides, the dislocation activities caused by SMAT result in the gradual breakdown of precipitates into smaller sizes and final dissolution in the matrix, increasing the number of nucleation sites and leading to more grain refinement processes. The grain boundary, dislocation densities, and the Cu-rich precipitate greatly influence the strengthening mechanism of surface-treated SS17-4PH.

The effect of weld heat input on the microstructure and mechanical properties of wire arc additively manufactured 15-5PH stainless steel

Precipitation hardening (PH) stainless steels, such as 15-5PH, have a high strength combined with excellent corrosion resistance. These properties make them valuable in critical industries such as defence, construction, aerospace, energy and maritime. Recent advancements in additive manufacturing (AM) technology enable the rapid and cost-effective production of components. In the case of 15-5PH components manufactured using wire arc additive manufacturing (WAAM), the as-deposited mechanical properties are not suitable at present for industrial applications. This paper explores the mechanical properties of this process and alloy combination without post weld heat treatment with the aim of eventual adoption in this condition by industry. The impact of weld heat input on the microstructure and mechanical properties of stainless steel 15-5PH produced using WAAM was investigated. The microstructure was examined using hardness testing in addition to optical and electron microscopy. Furthermore, mechanical properties were measured with tensile and impact testing. Investigations were conducted on material produced using weld heat inputs of 0.223 kJ/mm and 0.565 kJ/mm. These results indicate that reducing the weld heat input leads to a minor decrease in strength but an 80% increase in impact toughness. This reduction in weld heat input is correlated with a 50% reduction in volume fraction of δ-ferrite while also noting a 55% increase in carbide precipitates. In addition, the fracture surfaces were predominantly cleavage or quasi-cleavage in morphology.

Orthogonal array and artificial neural network approach for sustainable cutting optimization machining of 17-4 PH steel under CNC wet turning operations

Sustainable manufacturing strives to increase output while minimizing resource usage, costs, and environmental impact. Tool longevity is crucial, considering material, power, and resource consumption. Challenges like chip removal, heat, and friction necessitate effective solutions. Cutting fluids, like rice bran oil, reduce temperatures, friction, and enhance tool life and surface quality. Research focuses on using rice bran oil with a TiAlN tipped tool to minimize friction and cutting forces. Taguchi's robust design and L-9 orthogonal array reduce experimental trials. Controllable factors include speed, feed, depth of cut, and rice bran oil flow rate, with surface roughness as the performance metric. Taguchi analysis improves turning performance, particularly with 17-4 PH stainless steel. Rice bran oil reduces frictional forces, enabling improved surface quality across all samples, promoting sustainability. Surface roughness (Ra) is notably influenced by feed rate and rice bran oil, contributing 58.06% and 49.5%, respectively. This research underscores the potential of optimizing cutting fluid and process parameters to enhance sustainability in manufacturing.

Microstructural and Mechanical Characterization of Selective Laser Melted 17-4 PH Stainless Steel: Effect of Laser Scan Strategy and Heat Treatment

Microstructural and Mechanical Characterization of Selective Laser Melted 17-4 PH Stainless Steel: Effect of Laser Scan Strategy and Heat Treatment

Nanometer-scale porosity evolution and mechanical properties of additively manufactured 17-4PH stainless steel

Understanding of the microstructure and mechanical properties of additively manufactured (AM) 17-4PH stainless steel has matured significantly, but combined wrought-level strength and ductility has yet to be achieved. Identifying the microstructural obstacle(s) impeding this milestone is critical for many future applications and industries interested in this AM alloy. In this work, microstructure, mechanical properties, and fracture behavior is evaluated for AM 17-4PH built via the laser powder bed fusion technique (LPBF) and heat treated via a broad range of techniques to achieve wrought-level 17-4PH strength. The highest strength/ductility was achieved with a two-stage hot isostatic press (HIP) and solution anneal (SA) treatment followed by an aging heat treatment, but wrought-level ductility could not be matched. Persistent nano-porosity (0.06–0.23 μm) was identified and correlated to fracture surface dimpling (R2 = 0.73–0.85) indicating a possible role in this ductility limitation. Contextualization of this study's mechanical properties dataset within the literature suggests that this observation is endemic to the current state-of-the-art processing techniques for AM 17-4PH.

Experimental Study on Turbine Blade Material

This experimental study investigates the nitriding effects on microstructure of wrought 17-4 PH stainless steel. Nitriding was carried out at 560 °C for 2 hours, resulting in significant improvements in hardness. Nitriding improves the hardness on the surface of the 17-4 PH steel and remains constant in the core. As a result of nitriding the harness increased 3.5 times the hardness of the wrought alloy. Microstructural analysis of both untreated and nitrided samples using a scanning electron microscope (SEM) equipped with energy-dispersive X-ray spectroscopy (EDS) revealed the formation of a nitride layer. The results show a relationship between nitriding temperature and nitride layer thickness, with higher temperatures leading to thicker layers.

Effects of heat treatment on the nano-indentation, corrosion and cavitation erosion behavior of 17-4PH stainless steel by laser surface melting

The effects of heat treatment on the microstructure, residual stresses, nano-indentation behavior, the resistance to the corrosion and cavitation erosion (CE) of 17-4PH stainless steel (17-4PH SS) by laser surface melting (LSM) were thoroughly investigated. Experimental results showed that the samples were mainly composed of martensite phase, and the NbC precipitations formed after heat treatment. The distribution of NbC precipitations was more uniform in the sample (S3) after solution treatment 3 h at 1040 °C + aging treatment 3 h at 480 °C. The grain size was increased for the samples after heat treatment. This heat treatment processing significantly reduced the residual stresses generated from the LSM process, and the nano-indentation behavior of the LSM samples after heat treatment was improved compared to that of the LSM sample without heat treatment. The S3 sample displayed the highest corrosion resistance as indicated by the low corrosion current density (icorr), high pitting potential (Epit) and high polarization resistance (Rp). The CE resistance of samples after heat treatment in 3.5 wt% NaCl solution was higher than that of the sample without heat treatment. Among them, the S3 sample exhibited the highest CE resistance, and its CE mass loss was only 59.5 % of the sample without heat treatment. The excellent CE resistance resulted from the appropriate combination of mechanical properties, corrosion resistance and self-recovery ability of the passivation film.

Effect of build-up orientation angle and printing speed on mechanical properties and micro- and macro-defect formation in 17-4 PH stainless steel components manufactured by Bound Metal Deposition

Effect of build-up orientation angle and printing speed on mechanical properties and micro- and macro-defect formation in 17-4 PH stainless steel components manufactured by Bound Metal Deposition

A Comprehensive Study on Microstructure and Wear Behavior of Nano-WC Reinforced Ni60 Laser Coating on 17-4PH Stainless Steel

The surface of 17-4PH martensitic stainless steel was laser-cladded with Ni60 and Ni60+nano-WC composites and a comprehensive investigation was conducted of the microstructure and wear mechanism. The findings demonstrate that despite the added nano-WC particles being fused and dissolved during laser cladding, they still lead to a reduction in grain size and a decrease in crystallographic orientation strength. Furthermore, the dissolution of nano-WC makes the lamellar M23C6 carbides transform into a rod or block morphology, and leads to the CrB borides becoming finer and more evenly dispersed. This microstructural evolution resulted in a uniform increase in hardness and wear resistance, effectively preventing crack formation. When the nano-WC addition increased to 20 wt.%, there was a 27.12% increase in microhardness and an 85.19% decrease in volume wear rate compared to that of the pure Ni60 coating. Through analysis of the microstructure and topography of wear traces, it can be inferred that as the nano-WC addition increased from 0 wt.% up to 20 wt.%, there was a gradual transition from two-body abrasive wear to three-body abrasive wear, ultimately resulting in adherent wear.

Effects of aging and shot peening on surface quality and fatigue properties of material extrusion additive manufactured 17-4PH stainless steel

Material extrusion additive manufacturing (MEX) gains increasing interest due to its cost-effectiveness. However, concerns arise regarding inherent MEX characteristics potentially affecting mechanical properties. This study investigates the effects of shot peening and heat treatment on MEX 17-4PH stainless steel. After shot peening, surface nanocrystalline and compressive residual stress are induced. Aging results in higher hardness and tensile strength with lower elongation, while shot peening results in higher surface hardness with minimal change in elongation. For fatigue properties of as-sintered specimens, Al2O3 particle contamination dominates at high cycle regimes, while other MEX surface inhomogeneities dominate at low cycle regimes. Furthermore, as-aged properties are dominated by all surface inhomogeneities, resulting in the non-improvement of fatigue performance compared to the as-sintered specimens. However, shot peening on the as-sintered specimens significantly enhances fatigue properties through the formation of surface nanocrystalline structures and the induction of compressive residual stress, albeit with the occurrence of wrapped corners acting as fatigue crack initiation sites. Remarkably, the combination of aging and shot peening yields the most improvement in fatigue performance, exhibiting behaviours akin to as-sintered specimens with shot peening but without the generation of wrapped corners. Instead, fatigue crack initiation sites shift to subsurface region’s inhomogeneities.

Short-term creep approach to redefining the role of 17-4PH stainless steel for high-temperature applications

The creep response of the 17-4PH martensitic age-hardening steel in H1150 state was investigated at 427 and 482 °C. Hardness measurements of the heads of the creep samples demonstrated that the material underwent additional age hardening during the high-temperature exposure. Microstructural investigations confirmed that the additional precipitation of carbides and the G-phase occurred at the lowest temperature. A set of constitutive equations previously developed to describe the creep response of particle-strengthened alloys was successfully used to obtain a comprehensive description of the experimental data. The value of the particle strengthening term was obtained from the hardness measurements and corresponded to the Orowan stress. The model accurately described the observed minimum creep rate dependence on the applied stress and explained the occurrence of lower values of the minimum strain rate observed during variable-load experiments.

Structured porous 17-PH stainless steel layer fabrication through laser powder bed fusion

ABSTRACT This study aimed to fabricate thin, porous layers of 17-4 PH stainless steel with a defined porosity using laser powder bed fusion (LPBF). The central composite design (CCD) approach was utilized to examine the effect of process parameters on porosity. Three different methods were employed to measure the porosity of 17-4 PH stainless steel samples, i.e. theoretical analysis, buoyancy, and X-ray computed tomography (X-CT). A statistical quadratic regression model is generated that correlates with LPBF parameters to forecast porosity with high prediction accuracy. The maximum obtained porosity is 51.25% ± 0.33% with a laser power of 60 W, a scanning speed of 1800 mm/s, and a hatch spacing of 0.115 mm, which resulted in an average pore size of 24.8 ± 0.38 µm. Permeability was also analysed, as the volume energy density decrease ranges from 19.30 to 14.22 J/mm3, the permeability coefficient increases from 1.39 to 9.41 × 10−11 m2. In addition, it is observed that the minimum energy density to fabricate the 17-4 PH SS with the highest porosity and free of defects and fragmentation is 14.2 J/mm3.

Effect of construction angles on the microstructure and mechanical properties of LPBF-fabricated 15-5 PH stainless steel

In this study, 15-5 PH stainless steel were fabricated by laser powder bed fusion (LPBF) at different construction angles (0°, 30°, 45°, 60°, and 90°). Effects of construction angles on the microstructure, mechanical properties, electrochemical properties and surface characterization of 15-5 PH stainless steel were investigated. The LPBF-fabricated 15-5 PH stainless steel exhibited a “track-track” overlap trajectory on the horizontal plane, and the vertical plane displayed the “layer-layer” overlap of the melt pool. All samples were composed of martensitic and austenite phases. Irregular grains and random grain orientation were found in each sample. In fact, the construction angle has an important role in the microstructure. The 0° sample has the lowest martensite content (75.8%), since fewer deposited layers correspond to less number of thermal cycles. Due to the largest amount of martensite (90.1%), the 45° sample exhibits the highest hardness of 308.9HV0.2. The similar tensile strength and yield strength are achieved for samples fabricated at different forming angles. Layer by layer melt pool boundary (MPBs) contributes to the ductile deformation, whereas track by track MPBs is favorable for brittle deformation. Samples with a larger construction angle have more layer by layer MPBs, resulting in the increased elongation. Therefore, the 0° sample shows a minimum elongation of 20.1%, but the 90° sample reaches a maximum elongation of 23.9%. The construction angle affects the corrosion resistance of the 15-5 PH SS by influencing the martensite content. As a result, the 0° sample, with the highest austenite content (24.2%), shows the best corrosion resistance and lowest roughness.

Study on bending fretting fatigue behaviour of 15-5PH stainless steel with different fretting regimes

The failure of the aircraft spline shaft was attributed to overstressing, cyclic bending loads, and other complex conditions. This study investigates the bending fretting fatigue behaviours and failure mechanisms of 15–5PH stainless steel. The study analysed the residual stress, microstructure, morphology, and chemical state of the worn surface and the fatigue failure mechanisms. The results showed that fretting wear significantly reduces the bending fatigue life. The surface residual stress transitions from compressive to tensile stress states. The value of residual stress increased, and the oxygen content of the worn surface was higher in the mixed fretting regime. Fatigue fractures occur at a depth of 50–100 µm below the surface in the present experiment.

Analysis of the causes determining dimensional and geometrical errors in 316L and 17-4PH stainless steel parts fabricated by metal binder jetting

This work aims at investigating the causes affecting the dimensional and geometrical accuracy of holes in metal binder jetting stainless steel parts. Parallelepiped samples with a through hole were produced using AISI 316L and 17-4PH powders, differing for diameter (3, 4, 5 mm), and position of the axes with respect to the building plane (6, 9, 12 mm distance). Dimensions and geometrical characteristics were measured at green and sintered state by a coordinate measuring machine, determining the dimensional change and the geometrical characteristics. As expected, the shrinkage of linear dimensions is anisotropic; moreover, change in volume and sintered density are significantly affected by the position in the printing chamber. Higher shrinkage was measured along building direction (Z) – 18.5 ÷ 19.5%, than in the building plane – 16.5 ÷ 17.5%, and slightly higher shrinkage – 0.5 ÷ 0.8% was measured along powder spreading direction (X) than binder injection direction (Y). A variation up to 3% in relative density of sintered parts depending on the position in the building plane was observed in 316L. The dimensional change of diameters generally confirmed the shrinkage predicted by the model previously developed—difference between real and expected dimensional changes lower than 3%, except for three geometries (4 ÷ 6%). The cylindricity form error of sintered parts was strongly underestimated by the prediction model (up to 0.15 mm), but underestimation was considerably reduced (generally lower than 0.05 mm) adding the cylindricity form error due to printing. Dimensional and geometrical accuracy of holes are strongly affected by shape distortion of the parallelepiped geometry, in turn due to layer shifting and inhomogeneous green density during printing, and to the effect of frictional forces with trays during sintering. Gravity load effect was also observed on the holes closest to the building plane. Future work will improve the reliability of the prediction model implementing the results of the present work.

Investigating the microstructure and mechanical properties in furnace brazing Ti–6Al–4V to 17-4 PH stainless steel dissimilar joint with BNi-2 filler metal

Due to the distinct physical and metallurgical characteristics of titanium and steel, the welding of these two materials poses challenges and holds significant importance. This study investigates the impact of brazing time and temperature on the microstructure and mechanical properties of dissimilar brazing between 17-4 PH stainless steel and Ti–6Al–4V using BNi-2 as a filler metal, focusing on the formation of brittle compounds like FeTi and Fe2Ti during the brazing process. The joint between these materials is commonly utilized in various industrial applications. The assessment involved the use of optical microscope, scanning electron microscope, shear – tensile test, microhardness test, and wettability measurement. Brazing of the base metals was conducted at temperatures of 1050/1100 °C for durations of 15 and 30 min to determine the optimal temperature and time combination. The results indicated that the best joint properties were achieved at 110 °C for 15 min, with an average shear strength of 38.46 MPa. Contact angle measurements revealed that BNi-2 exhibited superior wettability on 17-4 PH compared to Ti–6Al–4V. Furthermore, increasing the temperature from 1050 to 1100 °C led to a reduction in contact angle from 9.98 to 8.83° for 17-4 PH, and from 16.51 to 10.12° for Ti–6Al–4V indicating an improvement in wettability.

The Microstructure and Mechanical Properties of a 15-6 PH Stainless Steel with Improved Thermal Aging Embrittlement Resistance.

The evolution of the microstructure and the mechanical properties of a 15-6 martensite precipitated hardened (15-6 PH) stainless steel after thermal treatment and long-term aging at 480 °C were investigated. Compared with 17-4 PH steel, the content of Cr decreased and Ni increased in the newly developed 15-6 PH steel; therefore, reversed austenite formed after thermal treatment at 620 °C of the solution-treated 15-6 PH steel. Although the reversed austenite may reduce the strength of the steel, it is very beneficial for the inhibition of the aging brittleness of the steel. During the accelerated thermal aging at 480 °C, the Cu-rich phase gradually coarsened, and its crystal structure changed, while the reversed austenite phase sightly increased and the Charpy impact energy maintained a rather high value. The increase of the reversed austenite content can offset the reduction of the strengthening effect of the Cu-rich phase and therefore maintain an excellent impact property of the material after thermal aging.

Characterization of Microstructural and Mechanical Properties of 17-4 PH Stainless Steel by Cold Rolled and Machining vs. DMLS Additive Manufacturing

The 17-4 PH stainless steel is widely used in the aerospace, petrochemical, chemical, food, and general metallurgical industries. The present study was conducted to analyze the mechanical properties of two types of 17-4 PH stainless steel—commercial cold-rolled and direct metal laser sintering (DMLS) manufactured. This study employed linear and nonlinear tensile FEM simulations, combined with various materials characterization techniques such as tensile testing and nanoindentation. Moreover, microstructural analysis was performed using metallographic techniques, optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). The results on the microstructure for 17-4 PH DMLS stainless steel reveal the layers of melting due to the laser process characterized by complex directional columnar structures parallel to the DMLS build direction. The mechanical properties obtained from the simple tension test decreased by 17% for the elastic modulus, 7.8% for the yield strength, and 7% for the ultimate strength for 17-4 PH DMLS compared with rolled 17-4 PH stainless steel. The FEM simulation using the experimental tension test data revealed that the 17-4 PH DMLS stainless steel experienced a decrease in the yield strength of ~8% and in the ultimate strength of ~11%. A reduction of the yield strength of the material was obtained as the grain size increased.

Corrosion Fatigue Behavior of 6000 HP Fracture Pump of the Valve Body Under Different Plunger Stroke Times and Acid Fracture Fluid Environment

Abstract As a key equipment for oil and gas extraction, the fracture pump is prone to failure due to fatigue crack in the crossbore of valve body. First, under acid fracture fluid and different loading frequencies, the fatigue crack growth rate of 17-4PH stainless steel was obtained by test, and the test data were used the modified Paris law. Then it is applied to numerical simulations to research the fatigue crack growth behavior of the valve body. The results show that the higher the loading frequency in the fracture fluid, the lower the fatigue crack growth rate, which is consistent with the test results. The influence of the working pressure on the stress intensity factor of the crack front is greater than that of the plunger stroke times. The model accurately predicts the fatigue crack orientation and corrosion fatigue crack growth life of the valve body.