LASER CLADDED TiCN COATINGS ON THE SURFACE OF TITANIUM

Laser cladded coatings of TiCN were produced on the surface of titanium. To obtain the optimal techniques, several conditions were tested by varying the laser scanning rate. The choice of shielding gas was also studied. The cladded coatings were then evaluated from the surface mechanics point of view based on their microhardness. The microstructure of some interesting samples was investigated by optical micrographs （OM）. The results showed that under the condition of fixed pulse frequency and pulse width, the laser scanning rate and the shielding gas are the main factors influencing the components of coatings. TiCN coatings were decompounded and oxidized during the cladding process in the condition of no shielding gas of N2. X-ray diffraction results indicated that the composite coatings composed of TiCN, TiC, Ti2N, and TiO2 were produced using appropriate techniques. The results indicated that the best condition in terms of the surface microhardness is obtained when the scanning rate is 1.5mm/s, the pulse frequency is 15Hz, the pulse width is 3.0ms, and N2 is chosen as the shielding gas. The microhardness of the composite coatings is about 1331kg · mm^-2, which is about 4 times that of the substrate. The optical micrographs indicated that the cladding zone is made up of TiCN, TiO2 and some interdendritic Ti, but the diffusion zone mainly consists of the dendrites phase, and the cladded depth is about 80μm, which is more than 2 times that of the laser nitrided sample. There were no microcracks or air bubbles in the cladded sample, which was cladded using the above optimal techniques.

Tribological properties in seawater for Ti/TiCN coatings on Ti6Al4V alloy by arc ion plating with different carbon contents

TiCN coatings incorporated with Ti buffer layer were deposited on Ti6A14V alloy by arc ion plating. The carbon content in TiCN coatings was varied by controlling flow rates of C2H2 in reactive gas. The Ti/TiCN coatings have a typical structure of columnar crystal with a total thickness of about 2 pro. The elements of Ti, C and N are present as TiN and TiC in TiCN coatings. A little free carbon appears with carbon content increasing in TiCN coatings. For the TiCN coatings, the hardness, friction coefficient and wear rate decrease with the increase in carbon content. In seawater, both friction coefficient and wear rate have an obvious decrease at lower carbon content compared with those in atmosphere. However, the friction coefficient and wear rate only have a slight decrease, while the carbon content reaches or exceeds 10 at% in Ti/TiCN coatings.

TiCN particle reinforce composite coating in-situ synthesized by nitrogen arc cladding technique

An in-situ synthesized TiCN particle reinforce composite coating was fabricated on Q235 steel substrate by nitrogen arc cladding technique, wherein the titanium powder and the graphite powder as original material were intensively mixed by ball-miU and glued with starch binder, then preplaced onto the Q235 steel substrate. The microstructures and interfacial behavior were investigated by scanning electron microscopy. The phase of the coatings was investigated by X-ray diffractometer. The microhardness was tested by microhardness tester. The anti-abrasive pe^Cormance was tested by abrasion machine. The results show that an excellent bonding between the coatings and carbon steel substrate is ensured by the strong metallurgical inteoCace and phases of the coatings are mainly composed of TiCN. The highest microhardness of the coatings reaches 810HV0. 5, which is about 3 times more than that of the Q235 substrate. The anti-abrasive test results indicate that the coating is more anti-abrasive than the Q235 substrate.

Tribological performance of uncoated and TiCN-coated D2,M2 and M4 steels under lubricated condition

Hard coatings are used to improve the wear resistance of metals which largely depends on adhesion between substrate and coating.The wear and friction behavior of uncoated and TiCN-coated D2,M2 and M4 steels were evaluated by apin-on-disk test under lubricated conditions.In order to evaluate the influence of lubricant on wear performance,dry friction tests were also performed.The results showed that friction coefficients were very similar for both uncoated and TiCN-coated steels.Under lubricated conditions,the uncoated D2 tool steel exhibited the lowest friction coefficient,but the TiCN-coated D2 steel presented the smallest wear rate.Abrasion was the main wear mechanism in all the tribocouples.Additionally,microhardness measurements were carried out,finding an influence of the steel substrate on the hardness of the coatings.Besides,adhesion test was conducted,suggesting agood adhesion of class 1 between substrates and TiCN coatings.