Microhardness Of Inconel Research Articles

Selective laser melting of Inconel 601 alloy using nanosecond fibre laser

The paper describes the impact of selective laser melting factors including using a nanosecond fibre laser, including laser powers, scanning speed, and thickness of layer, on the relative density and micro hardness Vickers of IN 601 samples was studied. Selective laser melting (SLM) is a commonly used powder bed fusion metal additive manufacturing (AM). Recent advances in additive manufacturing have attracted significant industrial interest, especially for producing metallic parts. Scanning electron microscopy (SEM), EDX and other techniques were utilized for studying the effect of speed of scanning and power of laser on densification behaviour, microstructural evolution and micro hardness of Inconel v alloy that was processed by SLM. With a VED of 3200 J/mm3, a scan speed of 250 mm/s with a 80 W, micro cracks of about 79-93 µm and voids of about (4.5 µm – 5.7) µm in diameter were realised. Moreover, the best hardness of 394 HV was attained with 80 W laser power. However, increasing the energy to more than the required values increased the porosity and decreased hardness. Using microsecond laser in SLM leads to the achievement of full density (almost 99.5%), whereas using nanosecond laser allows the achievement of less density (75-95%), which will be very useful for functions that require a porous structure and less weight, such as those in the aerospace applications, automotive industry and so on.

Graphene-strengthened Inconel 625 Alloy Fabricated by Selective Laser Melting

Graphene has been widely used as a reinforcement phase in composites due to its excellent electrical, thermal and mechanical properties. In this study, graphene was modified by electroless nickel plating to obtain nickel-coated graphene (Ni-Gr), which was then introduced into spherical Inconel 625 powder by ball milling. Selective laser melting (SLM) was subsequently used to fabricate Inconel 625/Ni-Gr metal matrix composites containing different levels of Ni-Gr (0, 0.4 vol%, 1.0 vol%). The effects of Ni-Gr content on the microstructure, mechanical, wear and corrosion properties of Inconel 625/Ni-Gr composites were investigated. Noticeable grain refinement was observed at the addition of 0.4 vol% Ni-Gr. The micro-hardness of Inconel 625/Ni-Gr composites increased with increasing Ni-Gr content and registered 348.2 HV0.2 at the addition of 1.0 vol% Ni-Gr. However, the Inconel 625/0.4Ni-Gr composite attained the maximum tensile strength (927 MPa), yield strength (797 MPa) and elastic modulus (227 GPa), aside from exhibiting lower friction coefficients than Inconel 625 at room temperature. In addition, it displayed higher corrosion potential than Inconel 625 and lower corrosion current density than Inconel 625/1.0Ni-Gr. The addition of Ni-Gr clearly improves the micro-hardness, tensile strength, yield strength, wear and corrosion properties of Inconel 625 due to grain refinement, solid-solution strengthening and impediment to dislocation motion. And, this study has verified the feasibility of preparing Inconel 625/Ni-Gr composites by SLM.

Strain Hardening Properties and the Relationship Between Strain and Hardness of Inconel 718

In micro-milling of Inconel 718, work hardening occurs and the strain hardening properties as well as the relationship between strain and hardness of Inconel 718 remain unclear. The quasi-static tensile tests are conducted in this paper. Through the experiments, the strength coefficient K and the strain-hardening exponent n in Hollomon formula, which describes the relationship between strain and stress of a material, are calculated. After the measurements of the micro-hardness of Inconel 718 under different plastic deformations, the relationship between micro-hardness and strain of Inconel 718 is established. This relationship is valuable in computation of the hardness based on the stress state of Inconel 718 and it also extends the application of the commercial finite element analysis software such as ABAQUS, since it tracks stress state but cannot acquire the hardness of the machined surface. The proposed equation then calculates the hardness value based on the simulation output of stress in the software. [Submitted 18 July 2017; Accepted 28 November 2017]