Tribology and high temperature friction wear behavior of MCrAlY laser cladding coatings on stainless steel

Temperature can have a significant effect on the extent of wear damage of metallic components. Thermal barrier coatings can improve the high temperature tribological and friction wear behavior. In this work the dry friction and wear behavior at low and high temperature of NiCoCrAlY and CoNiCrAlY laser cladding coatings were evaluated, as well as for the austenitic stainless steel AISI 304 used as substrate. Dense coatings, with good bonding to the substrate was obtained by coaxial laser cladding tracks (40% overlapping), with previously optimized laser parameters. Tribological wear tests were performed by sliding wear at room temperature and 500 ºC, with an Al2O3 ball on disk configuration tribometer. The wear scar surface was evaluated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) microanalysis. The 3D topography of the wear track was determined by inductive contact profilometer which enabled the wear rate calculation. The microstructure of the coatings consists of γNi/β-NiAl or γCo/β-(Co,Ni)Al phases depending on the chemical composition of the alloy, as confirmed by X-ray diffraction (XRD) analysis. The wear test results show a reduction in wear rate at high temperature for all materials tested. For the NiCoCrAlY coating, the high temperature also reduces the friction coefficient, while it significantly increases the friction coefficient of CoNiCrAlY coating. The main damage mode is abrasion and adhesion, caused by the oxide and partially-oxidized particles in the contact surface. The coatings and substrate results were compared, resulting in an improved wear behavior.The authors acknowledge the financial support of the Ministry of Science and Innovation of the Government of Spain through research project MAT2011-28492-C03 and the Generalitat Valenciana through ACOMP/2013/114 support. Professor Juan Carlos Pereira Falcon thanks the University of Carabobo (Grant CD3997-2011) for the financial support to pursue his doctoral studies at the UPV. Furthermore, the authors thank Dr. Jose Luis Jorda for the XRD analysis.Pereira, JC.; Zambrano, J.; Licausi, M.; Tobar, M.; Amigó Borrás, V. (2015). Tribology and high temperature friction wear behavior of MCrAlY laser cladding coatings on stainless steel. Wear. 330:280-287. https://doi.org/10.1016/j.wear.2015.01.048S28028733

Laser Cladding of MCrAlY coatings on stainless steel

MCrAlY alloys (where M stands for Ni,Co or both) are commonly used as overlay protective coatings in gas turbine engine components against high temperature oxidation and corrosion. The protective effect of these alloys is due to the formation of a continuous thermally stable oxide layer on the coating surface. In this work several types of MCrAlY alloys, differing in their elemental composition, have been deposited on austenitic stainless steel by means of laser cladding. The microstructure of the coatings have been characterized by SEM-EDS and XRD. As expected, elemental composition compatible with γ-Ni/γ'-Ni3Al, β-Ni/β'-NiAl or γCo/β-(Co,Ni)Al phases are observed in hypoeutectic or hypereutectic microstructures depending on the alloy composition. The high temperature oxidation behavior of the coatings was evaluated by air furnace oxidation tests at 1100ºC for 200 h. The oxidized surface of the samples was examined by SEM-EDS and the oxides present identified by theoretical stoichiometric calculations. Results indicate the formation of a uniform Al3O2 protective oxide scale with NiO, CoO, Y2O3/YAlO3 and Cr2O3 oxide inclusions.Tobar, M.; Amado, J.; Yáñez, A.; Pereira Falcón, JC.; Amigó Borrás, V. (2014). Laser Cladding of MCrAlY coatings on stainless steel. Physics Procedia. 56(C):276-283. doi:10.1016/j.phpro.2014.08.172S27628356

Manajemen Haji: studi kasus dan telaah implementasi

204

Kajian Business Process Reengineering untuk Penyempurnaan Prosedur Pendaftaran Haji

Penelitian ini dilakukan untuk mengetahui sampai sejauh mana efektifitas pelaksanaan prosedur pendaftaran haji dan kendala-kendala yang sering kali dan mungkin muncul. Rancangan prosedur pendaftaran haji didasarkan pada analisis Business Process Reenginering yang dimaksdukan untuk meningkatkan kualitas pelayanan publik melalui penyederhanaan prosedur pendaftaran haji, sehingga pelayanan pendaftaran calon haji dapat dilakukan secara efektif and efesien. Dalam konteks kinerja penyelenggaraan ibadah haji, yang didasarkan pada kajian konseptual-analitis BPR ini diharapkan Kementerian Agama dapat memberikan pelayanan prima kepada masyarakat dalam penyelenggaraan ibadah haji secara proporsional dan profesional dalam pelaksanaan tugas dan fungsinya. Penelitian ini bersifat deskriptif-kualitatif sebagai upaya untuk menjawab hipotesis utama tentang penyempurnaan prosedur pendaftaran haji, yang diarahkan pada tujuan pragmatis untuk meningkatkan pelayanan kepada masyarakat terkait penyelenggaraan ibadah haji. Secara pragmatis, kata kunci penyempurnaan dimaksud adalah upaya rekayasa ulang proses bisnis atas prosedur pendaftaran haji secara fundamental, radikal, dan dramatis. Subjek penelitian dalam kajian tesis ini adalah kebijakan prosedur pendaftaran haji yang diterapkan oleh Kementerian Agama sejak diberlakukannya sampai dengan saat ini. Responden dalam penelitian ini bersifat purposive sampling: pemilihan responden dilakukan secara sengaja sesuai dengan tujuan penelitian untuk mengidentifikasi dan menganalisis kondisi faktor-faktor internal dan eksternal serta rancangan prosedur pendaftaran haji yang akan dikembangkan dalam sistem pendaftaran haji. Rancangan prosedur pendaftaran haji didasarkan pada analisis Business Process Reenginering yang dimaksdukan untuk meningkatkan kualitas pelayanan publik melalui penyederhanaan prosedur pendaftaran haji, sehingga pelayanan pendaftaran calon haji dapat dilakukan secara efektif dan efesien. Hasil analisis atas penelitian ini menunjukkan bahwa proses rekayasa ulang serta rancangan baru prosedur pendaftaran haji lebih baik dari sistem lama terkait dengan beberapa aspek pelayanan dalam penyelenggaraan haji. Karenanya hasil penelitian ini memiliki signifikansi penting terkait penyelenggaraan ibadah haji secara keseluruhan

Menuju Rumah Sang Kekasih ; Rahasia Haji Mabrur

311 ha

The Sufi Path of Knowledge : Tuhan Sejati dan Tuhan-tuhan Palsu

xii, 450 hal., bibl.; 21c