Compared to conventional maraging steels, 18Ni300 has a high strength-to-toughness ratio and good machinability. It is used in industrial applications such as aircraft and aerospace manufacturing. It can also be heat treated. It can also be used to fabricate strong mould components.
The 18Ni300 belongs to the low-carbon iron-nickel alloys. It has a high friction coefficient, excellent machinability and good ductility. Over the past two decades, extensive research has been done on the microstructure of this alloy. It includes a mixture of martensite, intercellular RA and intercellular austenite.
The hardness value of the as-built sample was 41 HRC. It dropped to 32 HRC inside the region. This resulted from a homogenized microstructural change. This also corresponded with previous studies on 18Ni300. The hardness value increased to 39 HRC towards the 18Ni300 side of the interface. The incompatibility between heat treatment settings could have caused the difference in hardness.
The tensile strength of the wrought specimens was comparable to the direct aged samples. However, the solution annealed samples showed a higher fatigue strength. This was due to lower nonmetallic additions.
The wrought specimens were washed and weighed. Wear loss was measured in a tribo-test. The friction coefficient was found to be 2.1mm. With increasing load at 60 M/s, the wear rate increased linearly. Lower speeds produced a smaller wear rate.
The AM-built specimen's microstructure showed a mixture of intercellular RA and martensite. These intermetallic nanometre-sized particles were distributed throughout the low-carbon martensitic structure. These inclusions reduce the mobility of dislocations, and contribute to greater strength. Also, the microstructure of solution-treated specimens was improved.
The FE-SEM EBSD analysis showed retained austenite and reverted austenite in the intercellular RA region. This was accompanied with a fuzzy fish-scale appearance. EBSD revealed the presence of nitrogen as a signal at 115-130 um. This signal corresponds to the thickness of the nitride coating. The EDS line scan showed a similar pattern for all samples.
The EDS line scan showed that the nitrogen content increased in the hardness depth profile and in the top 20 um. It also showed that the nitrogen content in the nitride layer corresponds to the compound layer seen in the SEM images. This indicates that the nitrogen content increases in the nitride layer as the hardness increases.
During the last two decades, the microstructure of 18Ni300 has been extensively studied. The focus is on the interfacial region, as this area is the site of fusion bonding between wrought 17-4 PH substrate and AM-deposited 18Ni300 powder. This region is considered the equivalent to the heat-affected zone in the case of a tool steel. In the case of AM-deposited 18Ni300, nanometre-sized intermetallic particles are homogeneously distributed throughout the low-carbon martensitic microstructure.
This morphology is the result of the interaction of laser radiation with the powder during the laser powder bed fusion process. This morphology is consistent with previous studies of 18Ni300 AM-deposited. In the upper regions of interface, the morphology is less obvious.
A higher magnification image shows very small precipitates at the triple-cell junction. These precipitates are more active at the cell boundaries. These particles create a dendrite-cellular structure as they age. This is a well-described feature in the literature.
AM-built specimens are more resistant to wear due to the combination of aging treatment and solution. This also creates more uniform microstructures. This effect is also exhibited in hybrid-built 18Ni300-CMnAlNb parts. It also results in higher mechanical properties. The solution and aging treatment reduces the wear component.
In addition, a steady climb of hardness was observed within the fusion zone, which was evidence of surface hardening due to the laser scanning process. The interface's morphology was a mixture of AM-deposited 18Ni300 melt pool and 17-4 PH substrates. The upper interfacial boundary of the 18Ni300 melt pool is also visible. It has been also demonstrated that partial melting of the substrate 17-4PH causes a dilution effect.
High ductility is a hallmark of the 18Ni300-17-4PH steel parts, which are a hybrid-built and age-hardened. This feature is important in the case of tool steels, as ductility is considered to be a key mechanical property. These parts are also strong and hard. This characteristic is largely due to the solution and aging treatment.
Plasma nitriding could also be done simultaneously with aging. Plasma nitriding increased the corrosion resistance and improved wear resistance. The 18Ni300 also had a higher ductility and greater strength due to this treatment. Large transgranular dimples are a hallmark of aged 17-4PH steel. This feature was also present in the HT1 specimen.
Various tensile properties of 18Ni300 maraging stainless steel were investigated and characterized. Different process parameters were also examined. The microstructure of the samples after heat treatment was examined and characterized.
The tensile properties of the specimens were evaluated by using a MTS E45-305 universal tensile testing machine. These tensile results were compared with those obtained from vacuum melted wrought counterparts. The specimens' tensile characteristics were similar to those of 18Ni300 wrought specimens. The tensile strength in the SLMed corrax sample was higher than the results from the tensile tests of wrought 18Ni300. This could be attributed the strengthening of grain boundaries.
The microstructure of the AB and aged samples was investigated and characterized by X-ray diffraction, scanning electron microscopy, and electron backscatter diffraction. The morphology of cup-cone fracture was observed in the AB samples. Large equiaxed holes were also observed in the fiber area. Intercellular RA was the basis of the AB microstructure.
The effect of solution treatments on 18Ni300 maraging steel was investigated. The study showed that solution treatments increased the fatigue strength and the microstructure of the parts. The results showed that the optimum comprehensive performance of 18Ni300 maraging stainless steel could be achieved by aging the parts for 3 h at 500degC. This is also a good way to eliminate intercellular austenite.
The L-PBF process was used to compare the tensile characteristics of the samples with those of 18Ni300. This process allowed the inclusion of nanosized particles into the material. It also prevented nonmetallic inclusions (which could have adversely affected the mechanical properties) from being detrimental to the parts. It also prevented the formation void defects. Measurements of indentation hardness, and indentation modulus were used to determine the parts' tensile characteristics.
Results showed that aged samples had higher tensile strengths than AB samples. This is a result of the formation of Ni3(Mo,Ti) during the aging treatment. The tensile properties in the AB sample are identical to the older sample. The tensile fracture morphology in the AB samples was ductile, and necking was seen on the fracture surfaces.
Compared to traditional wrought maraging steel, the additively manufactured (AM) 18Ni300 steel exhibits better corrosion resistance, increased wear resistance and fatigue strength. In addition, the strength and toughness of the AM alloy is comparable to that of its wrought counterparts. These results show that AM steel can be used in intricate tool and die applications.
The study focused on the microstructure and properties of the maraging 300 steel. To this end, a BAHR DIL805 A/D dilatometer was used to analyse the activation energy of the martensite phase. XRF was also used as a countermeasure. In addition, the chemical composition was determined with a ELTRA Elemental Analyzer CS800. The results of this study showed that the 18Ni300 steel is a low carbon iron-nickel alloy, which is characterized by an excellent cellular formation. It has good ductility and weldability. It is widely used in complex tool and die applications.
Results showed that the IGA alloy has a minimum fatigue strength of 125 MPa, while the VIGA alloy has a minimum of 50 MPa. In addition, the IGA alloy had a larger N and O wt% and higher vol% of titanium nitride. This resulted in the formation of fine nonmetallic inclusions.
The microstructure resulted in intermetallic particles which were arranged in low carbon martensitic structures. It also inhibited the mobility of dislocations. In addition, the presence of nanometre-sized particles was found to be homogeneous.
Solution annealing also improved the minimum fatigue strength for the DA-IGA alloy. In addition, the minimum fatigue strength of the DA-VIGA alloy was also increased by direct aging. This resulted in the formation of nanometre-sized intermetallic particles. The minimum fatigue strength of the DA-IGA steel was also slightly higher than that of the vacuum melted wrought counterparts.
The microstructure of the as-built alloy consisted of martensite and crystal-lattice defects. The grain size was in a range of 15 to 45 mm. The average hardness was approximately 40 HRC. However, the fatigue strength of the as-built alloy was significantly decreased due to small cracks on the surface.
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