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"Pada makalah ini dibahas karakteristik lapisan WC-Co hasil proses thermal spray dengan teknik HVOF (High Velocity Oxy-Fuel) yang akan diaplikasikan pada pada nosel roket RX-10Q guna menggantikan pelapis grafit masif yang berat. Untuk itu, dilakukan studi pengaruh kekasaran permukaan terhadap kekuatan lekat dan struktur mikro lapisan.Hasil yang diperoleh menunjukkan bahwa variasi tekanan proses penyemprotan (grit blasting) menyebabkan variasi kekasaran permukaan, dimana semakin besar tekanan yang diberikan, semakin kasar permukaan yang diperoleh. Namun, kekuatan kohesi lapisan dan kekerasan lapisan WC-Co tidak dipengaruhi oleh kekasaran permukaan tersebut. Hasil penelitianjuga menunjukkan bahwa tanpa proses persiapan permukaan, lapisan WC-Co thermal spray tidak dapat melekat dengan baik pada logam dasarnya. Analisa struktur mikro lapisan WC-Co menggunakan mikroskop optik dan Scanning Electron Microscope (SEM) menunjukkan bahwa lapisan WC-Co relatifpadat dengan komposisi bervariasi pada daerah berbeda. Terdapat indikasi terjadinya difusi W pada daerah antar-fasa yang berkontribusi pada tingginya kekuatan lekat lapisan.

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This research investigated the characteristics of HVOF (High Velocity Oxy-Fuel) thermal spray WC-Co coating to be applied on the nozzle of RX-100 rocket. In particular, it studied the effects of surface preparation on the mechanical properties and microstructures of the coating.

The results showed that the grit blasting pressure directly influences the surface roughness of the substrate, in -which the greater the pressure, the higher the surface roughness. However, the cohesive strength and hardness of the coating are not affected by the surface roughness. This research also showed that without grit blasting, the WC-Co coating can not be applied on the substrate. Microstructural analysis of the WC-Co coating showed that this coating is relatively dense with variety in chemical content on different area. An indication of the diffusion of Win the interfacial area was found, which is thought to contribute to the high strength of the coating."

"Overlaid asphalt onto concrete pavement is another alternative than regrooving; it creates a composite layer of concrete-asphalt. Monolithic concrete-asphalts depend on bonding at its interface and affected by direction, space and depth of grooving, quantity and may type of tack coat used. This research aimed to know the effect of grooving direction to shear resistance of the interface on concrete-asphalt composite layer. Three types of grooving: transversal, angle of 45° and longitudinal, used. Emulsied asphalt of CRS-I and cut back asphalt of RC-70 by quantity of 0, 2 l/m2and 0, 6 l/m2 applied as a tack coat. As the results, it is known that shear resistance of the interface on concrete-asphalt composite layer affected not only on grooving direction but also quantity of tack coat and normal force applied. For concrete-asphalt composite layer, the highest shear resistance given by transversal grooving direction and 45° angle of grooving direction is better than longitudinal grooving. For all grooving direction, CRS-I emulsified asphalt has a higher shear resistance than RC-70 cut back asphalt and changing of adhesiveness of RC-70 caused of normal force is more susceptible than CRS-I."