Effects of Different Substrates on the Formability and Densification Behaviors of Cemented Carbide Processed by Laser Powder Bed Fusion

Cemented carbide materials are widely applied in cutting tools, drill tools, and mold fabrication due to their superior hardness and wear resistance. Producing cemented carbide parts via the laser powder bed fusion (L-PBF) method has the advantage of fabricating complex structures with a rapid manufacturing speed; however, they were underdeveloped due to their low density and crack formation on the blocks. This work studied the effect of different substrates including 316L substrates, Ni200 substrates, and YG15 substrates on the forming quality of WC-17Co parts fabricated by L-PBF, with the aim of finding the optimal substrate for fabrication. The results revealed that the Ni200 substrates had a better wettability for the single tracks formation than other substrates, and bonding between the built block and the Ni200 substrate was firm without separation during processing with a large range of laser energy inputs. This guaranteed the fabrication of a relatively dense block with fewer cracks. Although the high laser energy input that led to fine crack formation on the blocks formed on the Ni200 substrate, it was found to be better suited to restricting cracks than other substrates.

Examining the Effect of Evaporation Field on Boron Measurements in SiGe: Insights into Improving the Relationship Between APT and SIMS Measurements of Boron

Understanding and resolving discrepancies between atom probe tomography (APT) and secondary ion mass spectrometry (SIMS) measurements of B dopants in Si-based materials has long been a problem for those in the semiconductor community who wish to measure B within the source/drain SiGe of a device. APT data collection of Si-based materials is typically optimized for Si, which is logical, but perhaps not ideal for field evaporation of B. Increasing the evaporation field well beyond the typically used 28Si2+:28Si+ ratio of approximately 10:1 up to a ratio of ~200:1 is demonstrated to improve B detection while retaining well-matched Si and Ge concentrations with respect to those measured by SIMS. A range of evaporation conditions are examined from a very low field with high laser energy to an extremely high field with extremely low laser energy demonstrating problems at both far ends of the spectrum and a sweet spot when the operating conditions used produce a 28Si2+:28Si+ ratio of approximately 200:1 (in terms of total counts of each ionization state), which is more than an order of magnitude higher than normally used conditions and results in nicely matched B, Si, and Ge APT measurements with those of SIMS.

Nuclear Fusion Effects Induced in Intense Laser-Generated Plasmas

Deutered polyethylene (CD2)n thin and thick targets were irradiated in high vacuum by infrared laser pulses at 1015W/cm2 intensity. The high laser energy transferred to the polymer generates plasma, expanding in vacuum at supersonic velocity, accelerating hydrogen and carbon ions. Deuterium ions at kinetic energies above 4 MeV have been measured by using ion collectors and SiC detectors in time-of-flight configuration. At these energies the deuterium–deuterium collisions may induce over threshold fusion effects, in agreement with the high D-D cross-section valuesaround 3 MeV energy. At the first instants of the plasma generation, during which high temperature, density and ionacceleration occur, the D-D fusions occur as confirmed by the detection of mono-energetic protonsand neutrons with a kinetic energy of 3.0 MeV and 2.5 MeV, respectively, produced by the nuclear reaction. The number of fusion events depends strongly on the experimental set-up, i.e. on the laser parameters (intensity, wavelength, focal spot dimension), target conditions (thickness, chemical composition, absorption coefficient, presence of secondary targets) and used geometry (incidence angle, laser spot, secondary target positions).A number of D-D fusion events of the order of 106÷7 per laser shot has been measured.