It has been successfully demonstrated that ceramic materials can be joined in the green
state without a second phase by using low pressure injection molded parts. The investigation of the
joining interface revealed that a high quality interface can be achieved by carefully adjusting the
different manufacturing steps. The use of monomodal particle size distribution in the used powder
CT3000SG is inferior to a broader particle size distribution obtained by replacing 33% of the finer
alumina powder by coarser CT1200SG. In this way the dewaxing process is significantly improved
when the wall thickness of the part exceeds 3 mm. The investigation of the mechanical properties of
the joined and sintered parts revealed, that the bending strength of the joined specimens achieved
about 80 % of the unjoined, monolithic specimens.
The influence of temperature and counterbody material on the tribological properties of a-C:H
coatings deposited on Cronidur 30 steel has been investigated in a lubricated ball on disk
contact situation with alpha-alumina and silicon nitride as counterbodies. The results show, that the wear volumes of the systems increase exponentially with increasing temperature, for alpha-alumina more than for silicon nitride. Two different wear mechanisms seem to have a
major influence: First, the abrasive action due to materials hardness and second, the tribo-oxidation when silicon nitride is counter material.
The influence of temperature and counterbody material on the tribological properties of a-C:H coatings deposited on Cronidur 30 steel has been investigated in a lubricated ball on disk contact situation. The results show, that the wear volumes of the system increase exponentially with increasing temperature. Two different wear mechanisms seem to have a major influence: First, the abrasive action due to materials hardness and second, the tribooxidation when silicon nitride is counter material.
Stick-slip and wear behavior of ceramic and polymer materials under reciprocating sliding conditions
(2013)
In many technical applications not only the actual friction coefficient is of importance, but rather the constancy relevant for the functionality. Due to inconstant ffiction values, positioning processes can be substantially influenced as well as vibrations can be induced. The appearance of this tribological effect, named stick-slip, depends on different factors such as sliding speed, relative humidity and ambient temperature occurring primarily after long operating periods. Beside ambient conditions the choice of materials in contact is the main influencing factor of an inconstant coefficient of friction during operating. Certain polymers are well known for their stick-slip tendencies in technical applications. These are on the one hand different modifications of PTFE (polytetrafluoroethylene) reinforced with glass fibers, bronze or graphite and on the other hand thermoplastics such as PE (polyester) or Pf (polyimide). The difference between static and dynamic values of the ffiction force is decisive for stick-slip phenomena. Furthermore, the stick-slip tendency of polymers strongly depends on the elastic material properties. Main softening material areas, which can be found in the contact, represent particularly vulnerable areas. The high friction value in the contact area decreases in most cases by increasing sliding speeds. However, beside polymers ceramic materials can also offer tendencies to stick-slip motion. Klaffke et al. already investigated the influence of ceramic materials on the stick-slip behavior in.
The interaction of nanosecond laser pulses in the ultraviolet wavelength range and femtosecond laser pulses in the near-infrared region with the semiconductor SiC and the composite compound SiCTiCTiB2 was investigated. Surface analytical techniques, such as XPS, depth profile (DP), and micro-Raman spectroscopy (?-RS) were used to identify the chemical changes between untreated and laser-treated areas. Single-pulse irradiation led to material modifications in the condensed state in most instances. Multi-pulse results differed depending on the pulse duration. Crystal structure changes were observed as a consequence of laser-induced melting and resolidification. In air contact all components underwent oxidation reactions according to thermodynamic expectations. Exceptions were observed under exclusion of oxygen, SiC was reduced to elemental Si.
Tribological characterisation of siliconcarbonitride ceramics derived from preceramic polymers
(2006)
Amorphous SiCN ceramics were prepared in a laboratory scale as disk shaped specimens with 10 mm diameter and 0.3 mm thickness. The friction and wear behaviour was characterised in gross slip fretting tests under unlubricated conditions at room temperature against steel (100Cr6) and ceramic (Al2O3). Tests with a ball-on-disk contact were performed in laboratory air with different content of water vapour. The results show clearly that the relative humidity has a significant effect on friction and wear behaviour. All tests in dry air lead to higher friction and higher wear rate than in normal air. Improved friction and wear behaviour was observed with increasing pyrolysis temperature up to 1100 °C of the SiCN specimens. This is attributed to increasingly better mechanical properties and higher stiffness of the amorphous network due to the evaporation of gaseous organic species and the formation of free graphite like carbon.