Papers by Keyword: Stainless Steel

Abstract: In this paper a comparative study regarding the temperature in milling process for some types of aluminum alloys and an austenitic stainless steel is presented. In order to measure the temperature two methods are used, non-contact method, using an infrared thermometer and a contact method with six thermocouples installed along the workpiece. From the point of view of cutting parameters, for the both methods, different rotational speed and depth of cut were used, while feed speed was kept constant.

Abstract: Diamond-like carbon (DLC) coatings are valued for their excellent wear resistance and ability to extend the life of mechanical components, supporting resource conservation. However, high residual stress and poor adhesion limit their practical use. Silicon-doped DLC (Si-DLC) can reduce stress and improve adhesion, though excess silicon lowers hardness, creating a trade-off. This study aimed to optimize both adhesion and hardness by adjusting the silicon-containing gas ratio and the number of stacked layers. Si-DLC was deposited on austenitic stainless steel (SUS304) using acetylene (C₂H₂) and tetramethylsilane (TMS) via plasma enhanced chemical vapor deposition (PECVD) at 170 °C with a 1.2 µm thickness. Higher TMS ratios increased silicon and hydrogen content in the Si-DLC layer. More layers reduced hardness and low-load wear resistance but enhanced durability under high loads.

Abstract: Conventional plasma nitriding can induce defects due to direct plasma formation on the surface of the treated material. To address this issue, the screen-assisted direct current plasma nitriding (S-DCPN) method was developed, which generates plasma on both the sample and a surrounding screen, thereby reducing such defects. In this study, S-DCPN was applied to ferritic stainless steel (SUS430) using austenitic stainless steel (SUS304) as the screen material. Treatments were performed at 633 K for 15 hours under gas pressures of 200 and 600 Pa, with varying gas compositions of 75 % N₂ – 25 % H₂, 50 % N₂ – 50 % H₂, and 25 % N₂ – 75 % H₂. To evaluate the effects of gas composition and pressure, a range of analyses was conducted, including X-ray diffraction (XRD), cross-sectional microstructural observations, glow discharge optical emission spectrometry (GD-OES), hardness testing, and corrosion testing. The results revealed the formation of the α_N phase, a supersaturated solid solution of nitrogen in ferrite, under all conditions. Nitrogen diffusion and surface hardness increased with higher hydrogen content, and corrosion resistance was notably enhanced under the 25 % N₂ – 75 % H₂ condition. These findings demonstrate the effectiveness of S-DCPN in improving the surface properties of ferritic stainless steel while maintaining or enhancing corrosion resistance.

Abstract: During the study of laser cladding processes for manufacturing of structural elements from high-alloy corrosion-resistant steel on a thin-walled base, the issue of reduction of the powder material corrosion durability, applied by such technologies, during their use in corrosive environments, was considered. The aim of this study is to determine the effect of laser radiation intensity, used to form a deposited layer on a thin-walled base made from AISI 316L high-alloy corrosion-resistant steel, on its corrosion resistance. Samples, utilizing a laser cladding method, developed for creation of structural elements on pre-made thin-walled parts, were tested for pitting and intergranular corrosion (IGC) resistance using standard methods. IGC resistance was assessed by optical metallography. According to the results of corrosion tests, it was determined that samples of the layers of high-alloy corrosion-resistant steel AISI 316L, applied utilizing laser cladding technology on a thin-walled base, made from high-alloy corrosion-resistant steel, can be considered resistant to pitting and intergranular corrosion, while maintaining the range of values of power density at 30...50.0 kW/cm². These results align with the results of various studies by other authors who have been testing similar cases in other industries. The results of this study were used for further development of laser surfacing technologies for thin-walled parts used in various extreme conditions and further deepening of knowledge about modern laser cladding processes and expansion of the scope of this technology.

Abstract: Food-grade piping and water transportation systems extensively use dissimilar welding between stainless steel and carbon steel, where cost-effectiveness and corrosion resistance are essential consideration. However, the fusion zone of dissimilar welds often observed microstructural inhomogeneities and hardness changes, thus compromising mechanical qualities and corrosion resistance. This study was seperated in two phases to investigate and optimize dissimilar welding between carbon steel and stainless steel in both plate and pipe applications. Phase 1 studied welding A36 carbon steel plate and A304 stainless steel using gas tungsten arc welding (GTAW) with ER308L filler metal, the effect of post-weld heat treatment (PWHT) holding time on the mechanical and microstructural propertie. PWHT was performed at 650 °C for 20 and 60 minutes. The 20-minute condition yielded an optimal combination of mechanical strength and microstructural refinement, while the 60-minute condition led to grain coarsening and reduced strength. Phase 2 extended the findings to pipe welding applications, adopting the 20-minute PWHT condition. Welding was performed on dissimilar joints between A106-B carbon steel pipe and A312 TP304L stainless steel pipe (2-inch OD) using ER308L and ER309L filler metals under 99.99% argon shielding. Tensile and hardness testing indicated that welds with ER309L offered superior mechanical performance. Microstructural analysis revealed delta-ferrite and stabilized austenite in the fusion zone, with enhanced Cr and Ni concentrations contributing to improved corrosion resistance, as confirmed by electrochemical testing.

Abstract: In this study, Taguchi-L18 design is applied to cut AISI 304 stainless steels based on surface roughness under the effects of main control factors through un-coated carbide (K10 grade) and TiAlN coated carbide. The orthogonal array and analysis of variance are utilized to examine the performance characteristic when turning steel bars. A linear regression analysis is carried out to find out the relationship between input parameters and output. In addition, the chips are collected by both cutting inserts to see the morphology. The experimental results indicated that optimal levels were determined at 190 m/min speed, 0.076 m/rev. feed rate, 1.4 mm depth of cut when used TiAlN coating insert for surface roughness. Pareto chart and analysis of variance results revealed that feed rate was dominant, followed by coated tool and cutting speed in analyzing the surface roughness, but the coating was more effective than that of the speed. Further, it was concluded that correlation coefficients were around 93.8% for output. Confirmation tests were provided by Taguchi method and regression analysis. Moreover, the chips collected by TiAlN carbide inserts showed long narrow chips, leading to lower surface roughness because of obtaining the lowest feed rate/moderate speed and insert hardness in addition to providing the larger chip radius and chip length.

Abstract: Magnesium alloys are used more and more in automotive industry due to specific strength (ratio between tensile strength and density) of 158kNm/kg versus 46kNm/kg in case of structural steel [1]. Another advantage of magnesium alloys is machinability, aspect and automated caste/extrusion. With this last procedure is possible to achieve high rate of productivity for complicate pieces, needed in automotive sector. Technologically, a big issue of magnesium alloy is its reactivity in contact with carbon steel, accentuated by high temperature and pressure from extrusion chambers.

Abstract: Welding is the process of permanently joining materials and tungsten inert gas (TIG) welding is widely used due to its precision, controlled heat input, and cost-effectiveness. This study investigates the stress corrosion behavior of TIG-welded 304L stainless steel in a saline environment, analyzing factors contributing to material degradation. The research involved tensile testing and fractographic analysis to characterize fracture modes and determine the key influences on mechanical strength. Additionally, a microstructural analysis of the heat-affected zone (HAZ) was conducted to assess changes induced by welding. The results indicate that exposure to a chloride-rich environment led to a reduction in mechanical properties, primarily due to the formation of corrosion-related compounds and material thinning. Fractographic analysis revealed a transition in fracture modes, highlighting the influence of corrosion on failure mechanisms. Furthermore, microstructural examination showed significant alterations in the HAZ, which affected the overall integrity of the welded joints. These findings contribute to a better understanding of corrosion-induced degradation in welded 304L stainless steel and provide insights for optimizing welding parameters to improve durability.

Abstract: This study investigates the surface roughness, hardness, and fatigue performance of AISI 316L walls produced via wire arc additive manufacturing (WAAM) under three different surface conditions: as-built, severe shot peened (SSP), and machined. The WAAM-printed walls exhibit typical layered structures with some surface irregularities due to thermal cycling. Surface roughness measurements show that the machined surface has the lowest roughness values (Ra = 0.43 µm), while the as-built surface displays significant roughness (Ra = 37.56 µm), which is decreased by SSP (Ra = 34.67 µm). SSP slightly improves overall smoothness but does not eliminate major surface irregularities. Hardness measurements indicate that the base material has uniform hardness across the wall, ranging from 200 to 220 HV, while SSP significantly increases surface hardness to 450 HV near the edges due to localized work hardening. SSP-treated surfaces improve fatigue resistance by inducing compressive residual stresses, with a fatigue limit of 198 MPa, compared to 75 MPa for the as-built surface. However, machined surfaces exhibit the best fatigue performance, with a fatigue limit of 223 MPa, owing to the elimination of surface defects and stress concentrators. While SSP enhances surface hardness and fatigue performance over the as-built condition, machining remains essential for achieving superior fatigue life and surface quality.

Abstract: Wire arc additive manufacturing (WAAM) is an additive manufacturing (AM) process that provides the manufacturing of complex part geometries with high building rates, making it suitable for various industrial applications. To design WAAM parts effectively and for the optimal post machining of functional surfaces, understanding of the distribution of mechanical properties within the built parts is essential. In this study the distribution of hardness of typical WAAM specimen is investigated. The influence of the distance to the building plate and to the sample edge are discussed with regard to the microstructure of WAAM parts. Furthermore, the hardness distribution of WAAM parts is qualitatively compared to the hardness distribution of laser-based powder bed fusion (L-PBF) parts.