Tippaban Palathai

Comparative Studies on Wear Behaviour of Sintered 316L Stainless Steels Loaded with h-BN and MoS2

Mechanical properties and wear behavior of stainless steel embedded with different solid lubricants were investigated. Hexagonal boron nitride (h-BN) and molybdenum disulfide (MoS2)-embedded 316L stainless steels (SS316L/h-BN and SS316L/MoS2) were prepared by powder metallurgy method. Various h-BN and MoS2 contents (10, 15 and 20 vol%) were mixed with 316L stainless steel powders and then sintered at 1200°C in H2 atmosphere for 60 min. The experimental results showed that small boride phase and h-BN powder occupied the pores in the microstructure of SS316L/h-BN composite whereas the MoS2 second phase occupied the pores of the sintered 316L matrix in the microstructure of SS316L/MoS2 composite. The addition of h-BN decreased the sintered density and hardness whereas that of MoS2 gave the opposite effect. Dry sliding wear behavior of composites was investigated by using pin-on-disc test rig at the sliding speeds of 0.1 and 0.2 m/s and the applied load of 3 N. The results showed that the MoS2 composites had higher wear resistance than the h-BN composite but the h-BN composite yielded a better friction reduction.

Effect of h-BN Content on the Sintering of SS316L/h-BN Composites

In this work, the three compositions of hexagonal boron nitride (10, 15 and 20 vol. %)-embedded 316L stainless steel (SS316L/h-BN) composites were prepared by a conventional powder metallurgy technique and then sintered at varying temperatures of 1100 to 1250°C for 60 min in H2 atmosphere. The h-BN content and sintering temperature were found to affect the microstructure and hardness of the composites. The hardness decreased with increasing h-BN content and was improved by increasing the sintering temperature. Microstructure results revealed that the boride phase was formed at the grain boundary at the sintering temperature higher than 1150°C and the boride phase formation was observed to transform the h-BN in the composites.

Tribological Properties of Flame Sprayed Hexagonal Boron Nitride/Polyetheretherketone Coatings

Hexagonal boron nitride (h-BN)/polyetheretherketone (PEEK) composite powders were deposited on carbon steel substrate via the flame spray coating technique. The content of hexagonal boron nitride with a mean particle size of 0.5 micrometer was varied from 2 to 8 wt% in this work. Tribological properties, namely specific wear rate and friction coefficient, at room temperature, 100 °C and 200°C were performed using Ball-on-Disc sliding wear test. At elevated temperature, h-BN could result in marked decrease in the friction coefficients and specific wear rates.

Scratch Resistance and Adhesion Properties of PEEK Coating Filled with h-BN Nanoparticles

Effects of h-BN particles on mechanical properties and adhesion of semi-crystalline poly (ether-ether-ketone) (PEEK) coatings were studied. PEEK powder was mixed with various contents of h-BN nanoparticle in ethanol under ultrasonic mixing. As-mixed powders were sprayed onto low carbon steel substrate with thermal spray technique. The hardness, scratch hardness, specific scratch wear rate, prevailing deformation mechanisms and adhesion were obtained from scratch tests by varying the applied load. The damage geometry on scratched polymer surfaces and scratch wear volume loss were examined using scanning electron microscope (SEM) and surface profilometer, respectively. The results indicated that the addition of h-BN content improved the hardness of the composite. In addition, the specific scratch wear rate and the adhesion between PEEK coatings and substrate decreased with increasing h-BN content. The poor adhesion resulted from the reductions of flow-ability and viscosity between PEEK and substrate caused by heat dissipation from the h-BN particles.