Due to the excellent performance in high strength, anti-temperature and anti-wear, ceramics reinforced metal base
composite material was used in some important fields of aircraft, aerospace, automobile and defense. The traditional
bulk metal base composite materials are the expensive cost, which is limited in its industrial application. Development
of laser coating of ceramics reinforced metal base composite is very interesting in economy. This paper is focused on
three laser cladding ceramics coatings of SiC particle /Al matrix , Al2O3 powder/ Al matrix and WC + Co/mild steel
matrix. Powder particle sizes are of 10-60μm. Chemical contents of aluminum matrix are of 3.8-4.0% Cu, 1.2-1.8% Mg,
0.3-0.99% Mn and balance Al. 5KW CO2 laser, 5 axes CNC table, JKF-6 type powder feeder and co-axis feeder nozzle
are used in laser cladding. Microstructure and performance of laser composite coatings have been respectively examined
with OM,SEM and X-ray diffraction. Its results are as follows : Microstructures of 3C-,6H- and 5H- SiC particles + Al
+ Al4SiC4 + Si in SiC/Al composite, hexagonal α-Al2O3 + cubic γ-Al2O3 + f.c.c Al in Al2O3 powder/ Al composite and
original WC particles + separated WC particles + eutectic WC + γ-Co solid solution + W2C particles in WC + Co/steel
coatings are respectively recognized. New microstructures of 5H-SiC in SiC/Al composite, cubic γ-Al2O3 in Al2O3 composite and W2C in WC + Co/ steel composite by laser cladding have been respectively observed.
A numeric model of velocity and concentration distribution of shield gas-metal powder two phases flow field output by
nozzle in laser cladding is established, and it is calculated by FLUENT software. In this model, the influences of
momentum and mass transmission in the two phases flow are taken into consideration. The analysis on metal powder
flow field velocity and concentration distribution with different process parameters (nozzle exit width w, initial gas flow
velocity u and initial powder concentration c at nozzle entrance, angle of inward and outward wall of nozzle α, Φ) is
conducted. The calculated results show that w mainly affects concentration and velocity magnitude, u mainly affects the
focused position and velocity magnitude, c mainly affects concentration magnitude, α and Φ mainly affects the focused
position and concentration magnitude. Under the process parameter conditions: w=1mm, c=0.1, u=3m/s,α=82 ° ,
Φ=68.5°, the same flow field is measured with DPIV technique. The calculated result agrees with the measured result,
which indicates that the established model is reliable. The model can be used to understand the influences with different
flow field process parameters and further design the nozzle size.
In this paper, 5Kw CO2 laser and a special CNC table were used to weld automobile double-linked gears with
20CrMnTi material and Y gap. A lot of evaluations on microstructure, defects and mechanical properties for welding
seam were examined by OM, SEM and X-ray diffraction. It was shown that deep penetration welding in the double-linked
gear could be achieved at optimum parameters of 2.6~2.8KW and 2M/min. Laser welding had a small distortion
of 0.0408mm in gear diameter. Microstructure of fine martensite and austenite was observed in the welding seam.
Mechanical tests of hardness of HV400 and tordional strength of 1512Nm were measured. The welding seam had a
comprehensive intensity and toughness. The defects of blowhole and crack could be reduced or avoided by adjusting
parameter and preheating before welding. The allowable standard of laser welding of automobile double-linked gears
was recommended.
There are many expensive types of equipment in oil field on the sea from U.S.A or Europe in China. Some important components due to wear and erosion do not work; the large economic challenge needs laser recondition of the expensive parts. We have developed new laser cladding process for re-fabricating the long axle shaft and the body case in transferring oil pump in oil field on the sea. Using 5KW-CO2 lasers and the powder feeder, the cladding layer of NiCrSiB alloy on 40CrMo steel axle shaft with no crack and pores has been performed. The control distortion of long axle shaft during laser cladding has been researched. The laser re-fabricating has now been used to repairing production in the Bohai oil field in China.
This paper presents a special CAD/CAM software for rapid manufacturing thin wall metal parts by laser cladding, which is based on the developing of AutoCAD. It mainly consists of solid modeling, layering and section data processing, NC code generation module, processing path simulating and data transferring module.
Laser direct manufacturing and re-fabricating by co-axis feeding have been widely used in space, aircraft and power station. Due to lack of evaluation method of powder stream, its industrial application is limited in. A new Digital Particle Image Velocimetry (DPIV) system has been developed to measure the powder stream outside co-axis feeding head. The DPIV system is as follows: A double pulse Nd+:YAG laser, λ=532nm, single pulse energy 220mJ, pulse repeat frequency 10Hz, pulse width 6ns; Nd+:YAG laser beam shaping device; Frame straddle CCD camera, 30 frames/s, 8bit image plate and special image software. The transverse and longitudinal distributions of concentration and velocity fields have been measured by CCD camera respectively. It is shown that the focus parameters (focus diameter, focus length), concentration field, flow velocity field of powder stream can be successfully evaluated by the DPIV technique.
The quality of laser remanufacturing depends on temperature field distribution in laser molten pool. In this paper, two-dimensional temperature field model and CCD measurement of temperature field were developed. According to radiant transfer function, bright of light signal of temperature field grabbed by CCD was transformed to spectral radiant signal. A new system model for CCD measurement of temperature filed was proposed. It concluded optical system, CCD camera, image plate, orientating laser, special image software and computer. Thermal image signal received by CCD is transformed to digital signal by image plate. After processing digital image signal by computer, Temperature field distribution can be obtained by thermal image displaying. It was proved that CCD Measurement of molten pool temperature field was available. Automatic control of laser remanufacturing processing could be achieved by feedback control of thermal radiant signal.
Laser cladding technology has led to the development of a unique method for repairing, providing fast, near net shape reconstruction of components to blueprint dimensions. However, when the direction of the coaxial nozzle is out of the vertical with repairing surface, the powder feeder with carrying gas must be need. In this paper, the movement of gas particle two phase flow has been simulated with ANSYS software. The powder feed equipment with carrier-gas has been developed due to optimum design parameters. It mainly consists of two parts as follows: part one is alloy powder measurement unit, part two is convey powder unit with carrying gas. Lots of tests of powder transport with carrying gas with Ni02(45) aWC, were performed. The result is shown that it can solve problems of the superfine powders type transport and powder feed stabilization, moreover, it makes the precise feeding of powders possible, the powder feed rate 5~80g/min, catch efficiency up to 20%.
Laser Direct Materials Deposition(LDMD) is one of new emerging techniques of Rapid Manufacturing(RM) supported by CAD/CAM in recent years. Although LDMD shows great potential for many industrial applications, low powder efficiency about 30% due to canying gas increases cost of production and limits its application. In this paper, based on the Beer-Lambert law, the concentration ofpowder and the beam attenuation in co-axial feed powder laser cladding are researched. The relationship of the attenuation and laser cladding parameters, such as the laser power. a new co-axial powder feeder without carrying gas for LDMD was developed. Preliminary research on LDMD was achieved by non-carrying gas powder feeder.
A novel laser processing system for industrial surface engineering has been developed. It consists of wide-band laser scanner and wide-band powder feeder. It is used to laser cladding, alloying and surface hardening on the larger area, as well as welding. The system can provide single pass quenching or cladding widths with adjustable from 10 - 35 mm. The system was designed for delivering powder at precisely measured tolerance limits less than 2% and adjustable fed rate 0.5 - 200 g/min to produce the continuous, uniform and controlled laser cladding of 0.2 - 10 mm thickness, emphasis has been placed on repeatability, reliability as well as high powder utilization factor over 90%. All kinds of powders including not only Ni, Fe, Co and Cu base, but also ceramics powders ZrO2, Al2O3, WC and TiC can be fed. Without the carrier gas the powder flow depends mainly on gravity. It is successfully used to some surface engineering for metallurgical, automobile, oil and mechanical industries.
A novel beam optimization system, which provides static and linear beam pattern (SLP) for laser surface modification has been developed. Geometrical and physical theories were used to calculate the beam shaping distribution. The laser pattern experiment with the system has been made. It was shown the laser intensity distribution in the linear pattern was uniform, and the SLP widths can be adjusted from 15 to 25 mm continuously.
A new repair system for hardfacing of parts in metallurgical industries has been developed. The system can produce single pass quenching or cladding width of 10 - 35 mm, thickness of 0.5 - 10 mm. The wide range of powder materials can be deposited to provide hardfacing layers against wear, corrosion and oxidation. Comparing with welding and flame spraying, it presents clear advantages with low distortion, low dilution, low cost and small postclad machining. It has been successfully used to repair some of parts, for example, roll, drawing wire wheel in high speed wire, and so on.
In this work, a new laser cladding system on larger area for industrial application has been developed. It consists of wide-band scanning mirror and automatic powder feeder by the rotating feed wheel with bucket-type scoops. It is shown that all kinds of laser cladding powders including not only Ni-base, Fe-base, Co-base, but also superfine and light ceramics powders ZrO2 Al2O3 as well as superfine and heavy WC, TiC with spherical and edged grains can be fed. The powder feed rate can be continuously varied from 0.5 to 200g/min, and the measured tolerance limits are less than 2 percent in all conditions. The powder feeder can deliver powders by both side-band of 10-35mm and focusing band. Without the carrier gas the powder flow depends mainly on gravity. The powder stream at the nozzle is uniform, and the powder utilization factor is over 98 percent. Some applications in metallurgical industry have been successfully made.
In this paper, laser cladding of CuSnP alloy on HT2040 cast iron was investigated. By adding a proper ratio of Si or H3BO3 to improve the self-melting property of the CuSnP alloy and optimizing the processing parameters, a large area, homogeneous CuSnP clad was achieved. The metallographic structure of the laser clad is (alpha) -Cu + (beta) -Cu5Sn with hardness of Hv150.
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