A feasibility of in situ quantitative multielemental analysis during parts production by additive manufacturing technology (coaxial laser cladding) has been demonstrating for the first time using laser induced breakdown spectroscopy (LIBS). Compact LIBS probe was developed to equip the laser cladding head installed at industrial robot for analysis of key components (carbon and tungsten) during the synthesis of high wear resistant coatings of nickel alloy reinforced with tungsten carbide particles. It was demonstrated that the only acceptable choice for LIBS sampling was the melt pool due to non-uniform distribution of tungsten carbide grains in the upper surface layer. We have not observed any impact of melt pool ablation by LIBS probe on cladding process and clad properties according to clad cross-sections study by optical and scanning electron microscopies. The feasibility of in-situ LIBS quantitative elemental analysis of key components (carbon and tungsten) has been demonstrated during the cladding process. LIBS technique was demonstrated to be a good tool for real-time detection of cladding process failures. For example, failures with powder flows during cladding process resulted in undesirable variation of components concentrations and such problems were identified in real time by LIBS measurements.
We report results of design and optimization of high average power picosecond and nanosecond laser operating at 1342 nm wavelength. This laser is comprised of master oscillator, regenerative amplifier and output pulse control module. Passively mode-locked Nd:YVO4 master oscillator emits ~ 10 ps pulses at repetition rate of 55 MHz with average output power of ~ 100 mW. These pulses were used to seed regenerative amplifier based on composite diffusion-bonded Nd:YVO4 rod with variable Nd doping concentration pumped at 880 nm wavelength. Laser produces 10.9 ps pulses at 300 kHz repetition rate with average output power of 11 W and nearly diffraction limited beam quality M2 ~ 1.03. Fraction of laser output was converted to the second harmonics with 60 % efficiency providing the average power of 5 W at 671 nm wavelength. Without seeding the regenerative amplifier transforms to electro-optically cavitydumped Q-switched laser delivering 10 ns pulses at high repetition rates with beam propagation factor of M2 ~ 1.06.
We demonstrate results of design and optimization of high average output power picosecond laser operating at 1342 nm wavelength for selective material processing. This laser is comprised of mode locked master oscillator, regenerative amplifier and output pulse control module. Passively mode locked by means of semiconductor saturable absorber and pumped with 808 nm wavelength Nd:YVO4 master oscillator emits pulses of ~ 13 ps duration at repetition rate of 55 MHz with average output power of ~ 140 mW. The four-pass confocal delay line with image relay forms a longest part of the oscillator cavity in order to suppress thermo-mechanical misalignment. Optimization of the intracavity pulse fluence ensures significant lifetime improvement for the saturable absorber. This oscillator was used as the seeder for regenerative amplifier based on composite diffusion-bonded Nd:YVO4 rod pumped with 880 nm wavelength. When operating at 300 kHz repetition rate the laser delivers high quality output beam of M2 ~ 1.1 with average power in excess of 10 W at 1342 nm wavelength.