Experimental studies on gear-honing-tool with laser brazing film CBN
During the process of brazing cubic boron nitride (CBN) gear-honing-tool by Laser, cleaning of the gear-honing-tool and film plating CBN abrasive, and the thickness of brazing coating directly affect the quality and life of gear-honing-tool. In the paper, based on experiment the process of laser brazing CBN is summed up, the thickness interrelationship of brazing filler metal from beginning to end is obtained, the rule of laser facula's moving speed is studied on solder layer thickness and the radial change of gear tooth thickness. It is shown that the bonding among CBN, gear-honing-tool and solder can be realized by laser brazing. In order to improve quality of brazing, the moving speed of laser facula must be reduced along radial direction of gear honing tool. As to different size of CBN abrasive, the thickness of solder layer should be varied so that the bare rates of cutting edge can be ensured. The solder layer thickness should be controlled between 1.25 and 1.5 times of average size of abrasive grains. The thickness of solder layer depends on laser energy and soldering time that can be controlled by the moving speed of laser facula.
Joining of CBN abrasive grains to medium carbon steel with AgCu/Ti powder mixture as active brazing alloy
Abstract In order to develop new generation brazed CBN grinding wheels, the joining experiments of CBN abrasive grains and medium carbon steel using the powder mixture of Ag Cu alloy and pure Ti as active brazing alloy are carried out at elevated temperature under high vacuum condition. The relevant characteristics of the special powder mixture, the microstructure of the interfacial region, which are both the key factors for determining the joining behavior among the CBN grains, the filler layer and the steel substrate, are investigated extensively by means of differential thermal analysis (DTA), scanning electron microscope (SEM) and energy dispersion spectrometer (EDS), as well X-ray diffraction (XRD) analysis. The results show that, similar to Ag Cu Ti filler alloy, Ag Cu/Ti powder mixture exhibits good soakage capability to CBN grains during brazing. Moreover, Ti in the powder mixture concentrates preferentially on the surface of the grains to form a layer of needlelike Ti N and Ti B compounds by chemical metallurgic interaction between Ti, N and B at high temperature. Additionally, based on the experimental results, the brazing and joining mechanism is deeply discussed in a view of thermodynamic criterion and phase diagram of Ti B N ternary system.
Submicron polymer structures with X-ray lithography and hot embossing
This article describes the process chain for replication of submicron structures with varying aspect ratios (AR) up to 6 in polymethylmethacrylate (PMMA) by hot embossing to show the capability of the entire LIGA process to fabricate structures with these dimensions. Therefore a 4.7 μm thick layer of MicroChem 950k PMMA A11 resist was spin-coated on a 2.3 μm Ti/TiOx membrane. It was patterned with X-ray lithography at the electron storage ring ANKA (2.5 GeV and λc ≈ 0.4 nm) at a dose of 4 kJ/cm3 using a Si3N4 membrane mask with 2 μm thick gold-absorbers. The samples were developed in GG/BDG and resulted in AR of 6–14. Subsequent nickel plating at 52°C resulted in a 200 μm thick nickel tool of 100 mm diameter, which was used to replicate slit-nozzles and columns in PMMA. Closely packed submicron cavities with AR 6 in the nickel shim were filled to 60% during hot embossing.