K.V. Sreenivas Rao

Experimental investigation on erosive wear behaviour of plasma spray coated stainless steel

Slurry erosion is an implicit problem in many engineering industrial components such as ore carrying pipelines, slurry pumps and extruders. Even the water turbine blades are subjected to erosive wear when the water contains considerable amount of silt. In the present study, Al2O3-40%TiO2 powder particles of average particle size of 50 micrometer were deposited on EN56B martenistic stainless steel by atmospheric plasma spray technique. Ni/Cr was pre coated to work as bond coat for good adhesion between coating and the substrate material. A coating thickness of 200 micrometer was achieved. Coated and un-coated substrates were subjected to slurry erosion test as per ASTM G-119 standard. Slurry erosion test rig was used to evaluate the erosion properties at room temperature condition by varying the spindle speed. Scanning electron microphotographs were taken before and after the slurry erosion test. Microstructures reveal uniform distribution of coating materials. Eroded surface shows lip, groove, and crater formation and dense coating resulting in less porosity. Micro hardness test was evaluated and reported. EDX analysis confirms the presence of Al, Ti and O2 particles. It was observed that, Al2O3-40%TiO2 coated substrates exhibit superior erosion resistance as compared to un-coated substrates due to higher hardness and less coating porosity.

Dry Sliding Wear Behaviour of Al2O3 Coatings for AISI 410 Grade Stainless Steel

The wear and corrosion resistance of working surfaces can be improved by applying suitable coatings using thermal spray techniques. In the present work air plasma spray deposition technique (PSD) was used to coat Al2O3 ceramic powder on AISI 410 grade stainless steel. The steel substrate was primarily coated with Ni/Cr which acts as a bond coat for good fastening. Surface morphology of Al2O3 particulates of the coating was examined by scanning electron microscope (SEM). Uniform distribution of the Al2O3 particles on Ni/Cr pre-coated steel substrate was observed. Sliding wear tests under dry condition were conducted for different sliding velocity by keeping applied normal load and sliding distance constant. The results indicate significant improvement in the wear resistance of Al2O3 coated stainless steel substrate using PSD. The micro hardness of Al2O3 coated surface was found to be higher than that of the base metal.

Effect of Fibre Orientation on Specific Gravity, Hardness, Flexural Strength and Tensile Properties of Jute/Hemp Hybrid Laminate Composite

Bio-composites are taking over the polymer based composites due to their multi fold advantages. In this work, the natural fibre (jute-hemp) hybrid composite was prepared by traditional hand-lay-up method. The hardness, tensile and flexural properties of the composite specimen was evaluated in order to study the effect of fibres and fibre orientations using standard procedures. A significant improvement in hardness (114RHN), tensile (79.13mpa) and flexural (120.06mpa) properties were observed with fibre orientation of 900 compare to 300 & 450 orientations. Specific gravity test were conducted by using ASTM D792 standard at the temperature of 230c. The specific gravity was found to increase for 900 orientation of the fibre in the composite. It is also observed that the polyester based hybrid composite exhibits higher values of mechanical properties compared to epoxy based hybrid composites.

CFD Analysis of the Effect of Surface Contour of Nose Cone of a Space Vehicle on the Thermal Field during Re-Entry

When the space vehicle re-enters the earth’s atmosphere at a tremendous speed the frictional resistance creates enormous heat which may penetrate the vehicle leading to wreckage, if not dissipated to the surrounding. In the present study, CFD analysis of the thermal field generated on the surface of the solid model of the nose cone of the space vehicle is analyzed. Various configurations of the surface contour of the nose cone are considered to mimic the real life situation. The commercial CFD tool SolidWorks Flow Simulation module was used for the analysis. Four different surface contours were considered for the analysis of the temperature generated on its surface. The results indicate that the surface contour and re-entry velocity has a decided effect on the thermal field developed due to frictional resistance. Nose cone with larger half cone angle with small bluntness ratio offers greater resistance and hence lower temperature is generated compared to small half cone angle configuration.

A study on flammability and moisture absorption behavior of sisal/coir fiber reinforced hybrid composites

Cellulosic fiber reinforced Polymer Matrix Composites (PMCs) are more frequently applied in construction industry and transportation, in which their flammability and water absorption behaviors are important. Fire resistance of cellulosic fiber reinforced composites is important parameter that often limits the application of composites in a given area. This work presents experimental results of a fire retardant behavior and moisture absorption behavior of different weight percentage (10, 20, 30, 40 and 50 wt. %) of sisal/coir fiber reinforced epoxy resin hybrid composites. Traditional cold pressing method was used to fabricate hybrid composites. Flammability behavior of the hybrid composite was studied by using vertical and horizontal burning rates as per standard UL-94. Addition of the cellulosic fiber increases the flammability since natural fiber supports fire. It proves as a bad flame retardant due to the generation of a surface layer during pyrolysis of the cellulosic fiber which exhibits poor fire retardant nature. This layer acts as supporter of fire, which spreads the heat from being transferred to the un-pyrolised material. The speed of flame is much faster in vertical burning position compared to horizontal burning position due to preheating of the specimen. Moisture absorption of sisal/coir fiber reinforced epoxy resin hybrid composites are studied according to ISO 62:1999 standard procedure. Absorption of moisture increases with increasing in the reinforcement weight percentage of cellulosic fiber in fabricated hybrid composite.

Dry Sliding Wear Behavior of Ni-Cr/Micro-ZrO2 Coated AISI 410 Grade Steel-Final Revision

The most common industrial needs of coatings are to improve the surface properties such as, wear resistance, corrosion resistance and thermal conductivity/insulation. The use of expensive high strength materials and super alloys can be mitigated by using low grade materials covered with suitable coatings compatible with the media and service. Air plasma spray deposition method is used to achieve dense coating on substrate. The present research work demonstrates the wear properties of Ni-Cr/Micro-ZrO2 coating prepared through air plasma spray deposition (PSD) method. In this process, ZrO2 particulates of average particle size (10-40µm) were sprayed on Ni-Cr coated AISI 410 grade steel substrate. Distribution of ZrO2 particle was found uniform throughout the coating as revealed from SEM microphotographs. Dry sliding wear tests were performed on Pin-On-Disc Tribometer at room temperature with moderate humidity conditions. Significant improvement in wear performance was observed in Ni-Cr/Micro- ZrO2 coating deposited on steel via PSD which was also evident from worn surface morphology.

Laser Assisted Brazing of Ceramic and Titanium Alloy Using Cu-Ag Filler Material

The joining of ceramic to structural alloys has received much attention in recent years because of its potentially attractive properties. In the present investigation alumina which is a ceramic has been brazed with titanium alloy (Ti6Al4V) using KM72(Ag/Cu) filler material.The study has been carried out using CO2 laser gas in argon inert atmosphere. Uniformity of the brazed joints has been observed in scanning electron micrographs. The elements and phases present at the joint interface have been characterized by EDX and XRD spectra analysis. As per the experimental observation, the phases present in the Ti6Al4V/KM72/alumina joint are Cu3TiO4, Cu3Ti2,CuO, Ti2Cu, CuTi, and Cu4Ti3. The effect of brazing process parameters on the shear strength of the brazed joint has been studied and maximum shear strength observed at brazing power of 330 watts and speed 300 mm/min is 4±0.5MPa. Micro-hardness values of the brazed interface indicate that the interface is softer than the substrate.

Development of Corrosion Resistance Coating for AISI 410 Grade Steel

In this present research work, corrosion behaviour of grit blasted AISI 410 steel substrate coated with NiCr/Al2O3,NiCr/ZrO2 particles was investigated using salt spray test as per ASTM B117. Coatings were prepared using air Plasma spray process. Nickel chromium was used as bond coat for obtaining good fastening between the base metal and coated particles. The microstructures of the coated and un-coated specimens were characterized using scanning electron microscope and optical microscope. Distribution coated particle was found uniform throughout the steel substrate was revealed from SEM microphotographs. The obtained results shows significant improvement in corrosion resistance and micro hardness for NiCr/Al2O3 and NiCr/ZrO2 coating deposited on steel by plasma spray process than the as sprayed base steel substrates.

Effect of Mold Material on Boundary Heat Flux Transients during Gravity Die-Casting

Experiments were conducted to study the effect of mold material on boundary heat flux variation during gravity die-casting. Inverse method was used for determining heat flux on the inside and outside surface of the mold during casting of pure Aluminum and Al-B4C composites. Different chill materials were used as mold material on one side of the rectangular mold cavity. K- type thermocouples were used for measurement of mold temperature during casting solidification. The mold temperatures at various locations were recorded using a data logger. These measured temperatures were used as input by the inverse algorithm for the assessment of the surface heat flux as a function of time. It was observed that the temperature difference between the inner and outer surface of the copper is very less in comparison to the cast iron mold and stainless steel mold. The cooling curve of the insulation mold indicates that there is no heat transfer through the insulation mold. The boundary heat flux is much higher in the case of copper mold than in the cases of cast iron mold and stainless steel mold.