Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, dis...Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state welding process such as friction stir welding(FSW). In this investigation, a comparative evaluation of mechanical(tensile, impact,hardness) properties and microstructural features of shielded metal arc(SMA), gas metal arc(GMA) and friction stir welded(FSW) naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.展开更多
Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecor...Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecorrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosionecorrosion problems. High velocity oxy-fuel(HVOF)spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology(RSM) was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.展开更多
Friction stir processing and post process artificial ageing was successfully carried out on AA7075 with and without reinforcement of SiC particles producing defect free processed zone with uniform distribution of fill...Friction stir processing and post process artificial ageing was successfully carried out on AA7075 with and without reinforcement of SiC particles producing defect free processed zone with uniform distribution of filler material.Effect of SiC particle reinforcement and artificial ageing times on the microstructural modifications was characterized using optical and electron microscopy,electron backscattered diffraction and X-Ray diffraction.Hardness,impact and wear tests were carried out to investigate mechanical behaviour before and after processing.Reinforcement of SiC particles during FSP and subsequent age hardening treatment brought about nearly twofold increase in hardness and impact toughness values by the combined effect of grain refinement,Zener pinning,dispersion strengthening and precipitation hardening.Significant improvement in wear resistance in terms of wear loss was also observed after processing compared to the reference material AA7075-T6.Fractured surface of post FSP age hardened AA7075 alloy exhibited features of ductile fracture during Charpy impact test.展开更多
基金The Director,Naval Material Research Laboratory(NMRL),Ambernath for financial support through CARS project No:G8/15250/2011 dated29.02.2012
文摘Naval grade high strength low alloy(HSLA) steels can be easily welded by all types of fusion welding processes. However, fusion welding of these steels leads to the problems such as cold cracking, residual stress, distortion and fatigue damage. These problems can be eliminated by solid state welding process such as friction stir welding(FSW). In this investigation, a comparative evaluation of mechanical(tensile, impact,hardness) properties and microstructural features of shielded metal arc(SMA), gas metal arc(GMA) and friction stir welded(FSW) naval grade HSLA steel joints was carried out. It was found that the use of FSW process eliminated the problems related to fusion welding processes and also resulted in the superior mechanical properties compared to GMA and SMA welded joints.
文摘Flow based Erosion e corrosion problems are very common in fluid handling equipments such as propellers, impellers, pumps in warships, submarine. Though there are many coating materials available to combat erosionecorrosion damage in the above components, iron based amorphous coatings are considered to be more effective to combat erosionecorrosion problems. High velocity oxy-fuel(HVOF)spray process is considered to be a better process to coat the iron based amorphous powders. In this investigation, iron based amorphous metallic coating was developed on 316 stainless steel substrate using HVOF spray technique. Empirical relationships were developed to predict the porosity and micro hardness of iron based amorphous coating incorporating HVOF spray parameters such as oxygen flow rate, fuel flow rate, powder feed rate, carrier gas flow rate, and spray distance. Response surface methodology(RSM) was used to identify the optimal HVOF spray parameters to attain coating with minimum porosity and maximum hardness.
基金The authors would like to acknowledge National Facility for Texture and OIM(A DST-IRPHA project),IIT Mumbai for XRD and EBSD measurements.One of the authors VDH would like to acknowledge Science and Engineering Research Board(SERB)for financial assistance(EEQ/2016/000422)to carry out project work.
文摘Friction stir processing and post process artificial ageing was successfully carried out on AA7075 with and without reinforcement of SiC particles producing defect free processed zone with uniform distribution of filler material.Effect of SiC particle reinforcement and artificial ageing times on the microstructural modifications was characterized using optical and electron microscopy,electron backscattered diffraction and X-Ray diffraction.Hardness,impact and wear tests were carried out to investigate mechanical behaviour before and after processing.Reinforcement of SiC particles during FSP and subsequent age hardening treatment brought about nearly twofold increase in hardness and impact toughness values by the combined effect of grain refinement,Zener pinning,dispersion strengthening and precipitation hardening.Significant improvement in wear resistance in terms of wear loss was also observed after processing compared to the reference material AA7075-T6.Fractured surface of post FSP age hardened AA7075 alloy exhibited features of ductile fracture during Charpy impact test.
