Microstructure and Nanoindentation Properties of Surface Textures Obtained by Laser Machining and Molding in Silicon Carbide (original) (raw)

Chemical Assisted Laser Beam Machining of SiC Ceramic and Optimization of Process Parameters

2021

Chemo mechanical laser beam assisted finishing is the process of a conceptual combination of a fundamental cognitive process. In this process, three basic concepts are synthesized to obtain a smooth surface of silicon carbide. Three different chemicals of H2SO4 , HCl, and HF with a 50% solution with purified water were used. Continuous mode CO2 power from 250W-300W was used to melt the surface after acid was applied. The smooth surface was evaluated using morphology, including pore pattern, pore depth, and pore width was studied under a scanning electron microscope, and the surface roughness, wear-resistance, and hardness were analyzed using a non-contact surface profilometer, scratch tester TR-101, and Digital Rockwell hardness device respectively. The results were statistically analyzed using Design expert software analysis of variance (ANOVA). The results showed a significant change in the pore pattern, crystal structure, surface roughness, wear-resistance, and hardness. This res...

A Feasibility Study on Laser-Mechanical Drilling of SiC Ceramics

Key Engineering Materials, 2010

Structural SiC (α-type) is believed to be widely applied in hostile environments such as high-temperature, high-corrosive applications in the semiconductor industries due to its superior thermo-physical and mechanical properties. However, the extremely high hardness and brittleness of SiC makes hole drilling difficult by the conventional mechanical drilling (CMD) technique. Laser can be used to drill SiC; but the resultant holes are often tapered and uneven, with tendency for microcracks and thermal damage to occur at the hole entry due to the high thermal shock from the laser. This paper reports on the experimental results of a sequential laser-mechanical drilling (LMD) technique for drilling α-SiC. At first, an Nd:YAG laser was used to drill a series of pilot holes on a 3 mm thick SiC plate. Then a diamond-coated carbide drill was sequentially applied to these holes to obtain desired hole diameter of 0.5 mm. A number of through holes on SiC (aspect ratio: 6) were successfully obtained using this approach. The quality of the drilled holes were assessed in terms of the entrance and exit sizes and conditions, hole taper angle, hole edge shapes, and microcracks. Finally, comparisons of the LMD performances were also made against the holes predrilled by the laser itself and holes of the similar size drilled separately with the CMD technique. The experiment results show that the proposed drilling approach can effectively drill α-SiC ceramics.

Processing of silicon carbide by laser micro sintering

Silicon carbide -a solid with covalent bonds -is conventionally synthesized via the Acheson process. Usually solid bodies of silicon carbide with definite shapes are generated from the grained material via hot isostatic pressing or liquid phase sintering. Both processes are conducted under well-controlled temperature regimes. Applying the freeform fabrication technique "Laser Micro Sintering" poses a big challenge to experimental skill due to the nonequilibrium conditions that are characteristic features of laser material processing.

Micro-Laser Assisted Machining (µ-LAM): Scratch Tests on 4H-SiC

wmich.edu

In the nanomachining of semiconductors and ceramics, especially brittle materials such as silicon carbide, the presence of high pressure phase transformation is of great importance for accomplishing ductile regime machining [1]. To augment the ductile regime machining of these nominally brittle materials, the high pressure phase can be preferentially heated and thermally softened by using concentrated energy sources such as laser beams [2]. Notably, the results of scratch tests at 1µm/sec show a doubling of the scratch depth which suggests a ~40% reduction of calculated relative hardness due to thermal softening by the laser heating.

Surface characterisation of laser irradiated SiC ceramics by AES and XPS

Fresenius Journal of Analytical Chemistry, 1999

Samples of sintered silicon carbide (SSiC) were irradiated with a KrF excimer laser (λ = 248 nm) at energy densities of 10, 15 and 25 J/cm2 in He atmosphere. The composition of the near surface region was investigated by Auger electron spectroscopy (AES) and photoelectron spectroscopy (XPS) after lapping, laser irradiation and tribological treatment, respectively. By laser irradiation a surface layer is formed which contains about 30% oxygen. The existence of different bonding states of Si, C and O was established by factor analysis of the AES depth profiles and by XPS. By laser irradiation SiC is decomposed and a siliconoxycarbide with the average composition SiC3.5O1.5 is formed. Beneath the oxidised surface layer the nominal elemental composition SiC is found but the sample represents a mixture of Si, graphite and siliconoxycarbide with a small amount of SiC only. Obviously, the decomposition zone exceeds in a depth > 300 nm.

Laser irradiation of α-SiC ceramics

Ceramics International, 2009

The process of laser irradiation of a surface of SiC ceramics in air was investigated. As a result of SiC oxidation and evolution of CO 2 , porous SiO 2 forms on the target surface. During deposition of ablation products on the substrate, a loose SiO 2 film forms. #

Selective Laser Sintering of Polymer-Coated Silicon Carbide Powders

Industrial & Engineering Chemistry Research, 1995

Selective Laser Sintering (SLS) produces three-dimensional objects directly from a computeraided design (CAD) solid model, without part-specific tooling, by repeatedly depositing thin layers of fusible powder and selectively sintering each layer to the next with a rastered, modulated, CO, laser beam. This technology, originally intended to produce parts and patterns from powdered waxes and thermoplastics, can be extended through use of thermoplastic-coated inorganic powder to producing "green" shapes which contain metal or ceramic powder bound together with the thermoplastic. These shapes can be subsequently processed into metal, ceramic, or composite metayceramic parts by various methods. Generally, the strength of the green shape critically depends on the layer to layer fusion that is achieved. A model of the SLS process is presented that correctly estimates the sintering depths in poly(methy1 methacrylate) (PMMA) and coated silicon carbide (Sic) powders that result from operating parameters including laser power, beam scanning speed, beam diameter, scan spacing, and temperature. Green part densities and strengths are found to correlate with a combination of parameters, termed the energy density, that arise naturally from consideration of the energy input to the powder bed.