Temperature monitoring in the laser impact zone is carried out by an originally developed bi-colour pyrometer which is
integrated with the optical scanning system of the PHENIX PM-100 machine.
Experiments are performed with variation of basic process parameters such as powder layer thickness (0-120μm), hatch
distance (60μm-1000μm), and fabrication strategy (the so-called "one-zone" and "two-zone").
To up-grade selective laser melting (SLM) process for manufacturing real components, high mechanical properties of
final product must be achieved. The properties of a part produced by SLM technology depend strongly on the properties
of each single track and each single layer. In this study, effects of the processing parameters such as laser power,
scanning speed and powder layer thickness on the single tracks formation are analyzed. It is shown that, by choosing an
optimal technological window and appropriate strategy of SLM, it is possible to manufacture highly complex parts with
mechanical properties comparable to those of wrought material.
Optical monitoring of temperature evolution and temperature distribution in laser machining provides important
information to optimise and to control technological process under study.
The multi-wavelength pyrometer is used to measure brightness temperature under the pulsed action of Nd:YAG laser on
stainless steel substrates. Specially developed "notch" filters (10<sup>-6</sup> transparency at 1.06 μm wavelength) are applied to
avoid the influence of laser radiation on temperature measurements. The true temperature is restored based on the
method of multi-colour pyrometry.
Temperature monitoring of the thin-walled gilded kovar boxes is applied to detect deviation of the welding seam from its
The pyrometers are used to control CO<sub>2</sub>-laser welding of steel and Ti plates: misalignment of the welded plates, variation
of the welding geometry, internal defects, deviation of the laser beam trajectory from the junction, etc. The temperature
profiles along and across the welding axis are measured by the 2D pyrometer.
When using multi-component powder blends in laser cladding, for example metal matrix composite with ceramic
reinforcement, one needs to control temperature of the melt to avoid thermal decomposition of certain compounds (as
WC) and to assure melting of the base metal (as Co).
Infra-red camera FLIR Phoenix RDAS provides detailed information on distribution of brightness temperature in laser
cladding zone. CCD-camera based diagnostic system is used to measure particles-in-flight velocity and size distribution.
Laser assisted direct manufacturing and in particular Selective Laser Melting (SLM) becomes a promising manufacturing
technique. Recent progress makes it possible to create fully functional parts directly from metal powder without using any
intermediate binders or any additional processing steps after laser melting.
At present only a few studies were carried out to monitor and to on-line control SLM process. In this paper, the optical
diagnostic tools as infra-red camera and pyrometer are applied for SLM process visualization and control : surface
temperature evolution, phenomena in laser-powder interaction zone, dynamics of droplets emitted from the molten pool.
Advanced pyrometers were applied for surface temperature monitoring during Nd:YAG laser pulsed and pulsed-periodic action on circuit breaker contacts (Ag based composite material with graphite inclusions). Temperature evolution, heating and cooling rates, melting threshold are measured and discussed.
The set of original pyrometers and the special diagnostic CCD-camera were applied for monitoring of Nd:YAG laser cladding (Pulsed-Periodic and Continuous Wave) with coaxial powder injection and on-line measurement of cladded layer temperature. The experiments were carried out in course of elaboration of wear resistant coatings using various powder blends (WC-Co, CuSn, Mo, Stellite grade 12, etc.) applying variation of different process parameters: laser power, cladding velocity, powder feeding rate, etc. Surface temperature distribution to the cladding seam and the overall temperature mapping were registered. The CCD-camera based diagnostic tool was applied for: (1) monitoring of flux of hot particles and its instability; (2) measurement of particle-in-flight size and velocity; (3) monitoring of particle collision with the clad in the interaction zone.