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Metal additive manufacturing (AM), often known as 3D printing, is revolutionizing the production of complex engineering components by constructing them layer by layer. This innovative process utilizes a high-energy heat source and various materials, such as powder, wire, or sheets, as feedstock. The latest review is focused on the progress made in AM, with its potential to produce steel materials of outstanding properties that cannot be matched by conventional manufacturing techniques. This is mainly attributed to the characteristic microstructural changes in the course for AM. This review indicates that many steel types could be process successfully with AM processes. The microstructure, consisting of hierarchical (sub) grains and fine precipitates formed in the process, is largely responsible for its high strength and wear resistance relative to conventional steel. However, ductility remains an issue with AM steels. Moreover, additive manufacturing is an intrinsic heat treatment process and “in situ” phase transformations such as tempering and different type of precipitations are possible when applied to a range of steel grades. In short, the review amply discusses the effects of these unique microstructure features on the properties of steels made by AM.

This study focuses on exploring the synergistic effects of combining two processing practices: additive manufacturing and hot forming with varying hammer strokes (3HS, 5HS, and 7HS) on steel components. The investigation utilizes the WAAM technique with a MIG setup to create components on a low alloy steel substrate, employing diverse deposition patterns. Experiments were conducted using fully automated MIG welding on a low alloy steel substrate with ER70S-6 copper-coated steel wire. Samples were built using five different deposition patterns: longitudinal, transverse, right network, oblique, and oblique network. To evaluate the samples, various examinations were performed, including optical microscopy and scanning electron microscopy.

This study presents the impact of chloride ion present in the soil in contact with reinforced concrete in the initiation of corrosion of steel reinforcement. The factors affecting the corrosion process due to the penetration of chloride ion from chloride bearing soils in contact with concrete specimens, representing different reinforced concrete members, were studied. The results proved that there exists a threshold limit for the concentration of soil-borne chloride ion, to initiate the corrosion. The value of this limit was related to the thickness of the concrete cover, concrete grade, besides the type of exposure (number of sides exposed to chloride attack). It was shown that the safe percentage of chloride ion in the groundwater and soil in contact with concrete was 2% in aqueous extract (0.4% in soil) when the thickness of the concrete cover was not less than 50 mm. This proportion could reach 6% in aqueous extract (1.2% in soil), when the cover thickness was not less than 75 mm, or when the concrete possessed a 35 MPa compressive strength as well as exposed on one side only. Consequently, special limitations for the permissible proportions of chloride ion in soils in contact with reinforced concrete members should be established by design codes.

A pure copper powders were high energy milled for 1, 3, and 5 hours in addition to non-milled copper. Each case was divided into two groups to be sintered at 825º and 900º C. Mechanical properties of copper consolidated compacts were characterized to determine the effects of milling time and sintering temperature on modulus of elasticity, yield strength, ultimate strength, hardness, and surface resistance to mechanical wear. Powders which milled for one and three hours show enhancements in all properties (except wear resistance) when compared to non-milled powder. Put, powders which milled for five hours show even near or lower values compared to non-milled powder. Specimens sintered at 825º C have higher values of a specific property when compared to specimens sintered at 900º C, regarding their milling is the same. Wear resistance for non-milled specimen is better of the all, and specimens sintered at 900º C have higher resistance to mechanical wear more than those sintered at 825º C.

The effects of powder metallurgy variables on structural evolution in pure copper were studied here. Powders of pure copper were exposed to various periods (1, 3, and 5 hours) of high energy milling, in addition to non-milled case. Sintering in protected environment was accomplished. The consolidated parts then were characterized by XRD, EDS, and SEM to evaluate structural changes. Inspections revealed that a three dimensional treelike powder converted by milling to a rounded, flakey, granular, and other shapes of denser copper particles. Some agglomeration was noted. By increasing time of milling, agglomeration was increased too in first and mid stages, during last stage refinement was a dominant. EDS tests showed that both after milling and after sintering a high purity of products was recorded. Consolidated parts revealed a narrow grain size distribution for non-milled starting material, also, a wider size distribution for milled parts in addition to smaller grains sizes related to recrystallization, with some grain growth. By XRD, some extent of amorphous structure or loss in crystallinity was observed related to prolonged extensive plastic deformation, and it proportionated inversely to temperature of sintering. And this was in opposite to observations about grain growth and increased crystallinity in parts sintered in higher temperatures.

Thermal oxidation (TO) is one of the most important techniques in the field of surface modification to enhance the required properties of engineering materials. In the present study, the influence of TO process on the corrosion behavior of a commercial pure titanium (CP-Ti) was investigated. The oxidation process was conducted at different temperatures, i.e., at 500 and 800 oC for 8 h, in a muffle furnace with a controlled environment at atmospheric pressure. The characterization of modified surface layers was examined. It is found that TO process promotes the formation of adherent surface oxidized layers on the CP-Ti samples without spallation. The superior electrochemical performance is found in oxidized CP-Ti samples compared to untreated samples.