COMPARATIVE STUDY AND EVALUATION OF SPARE PARTS FOR SEPARATORS IN NAVAL APPLICATION

Transcription

1 COMPARATIVE STUDY AND EVALUATION OF SPARE PARTS FOR SEPARATORS IN NAVAL APPLICATION

2 Short Summary on Materials Testing and Analysis Parts that were analyzed Steel parts Polymer parts Worm with gearing Bowl Spindle Seal Rings Rectangular Rings O-Rings Heat treatable steel C45 Heat treatable steel C45 Polyamide PA66 Nitrile rubber compound NRC Nitrile rubber compound NRC Measurements performed during the study components no. of analyzed properties / measurements samples geometrical mechanical other 2 Worms (C45) Parts no Bowl Spindles (C45) Parts no Seal Rings (PA66) Parts no Rectangular Rings (NRC) Parts no /02/ Rings (NRC) Parts no bearing seats - gearing - bearing seats - cone position - diameter - height / width (upper - and lower face) - diameter - width - diameter - width - hardness / elastic indentation - modulus - hardness / elastic indentation - modulus - hardness - hardness - tensile strength - hardness - tensile strength - chemical analysis - metallography - chemical analysis - metallography - thermal analysis - microscopy - optical comparison - analysis extractable elements - spectroscopy - thermal analysis - optical comparison - optical comparison Steel Components: Worm with Gearing (part no ) Design sketch of Chiefmar worm component: Geometrical analysis of: quality of the gearing Gear measuring center dimensional and positional tolerances of the bearing seats 3D-coordinate measurement machine Position of component coordinate systems for worm and bowl spindle and planning of analysis of the dimensional and positional tolerances Gear measuring center: rotatable mounting device and measuring head

3 Quality of the Worm Gearing (Profile and Trace Analysis) Measurement report of the Chiefmar Measurement report of the Alfa Laval gearing Metallography of the Worm Gearing Chiefmar gear tooth, Overview Alfa Laval gear tooth, Overview Chiefmar gear tooth, Core material Alfa Laval gear tooth, Core material a grain size of Chiefmar material is slightly larger, pearlite is finer for Alfa Laval material mechanical properties will be poorer in small extent for Chiefmar components this effect is mainly for the near-surface region large difference in pearlite structure for material in the components' core suggests very slow cooling of the Chiefmar material will be improved by heat treatment of component after machining Light optical micrographs of gearing teeth, Chiefmar and Alfa Laval worms Left: overview of the microstructure Right: material in the center of the gear teeth with higher magnification

4 Microstructural Analysis of the Worm Bearing Seats (Metallography) Location of metallographic preparations: Chiefmar, bearing seat A, surface Alfa Laval, bearing seat A, surface analyzed positions: gearing and bearing seats location of the metallographic preparations Chiefmar, bearing seat A, core Alfa Laval, bearing seat A, core Hardness Analysis by Vickers Indentation on Worm Components Principle of the indentation test method for hardness measurement (Martens hardness): F = 0 F grain sizes are comparable differences are low between surface and core material α α h Chiefmar worm gearing tooth tip Alfa Laval worm gearing tooth tip Vickers hardness/depth profiles for bearing seats Table: Surface Vickers hardness of bearing seats Light optical microscopies of the indentations for Vickers hardness/depth profile analysis on worm gearing tooth tips Table: Vickers hardness, average values over the measuring depth for gearing teeth manufacturer bearing seat A bearing seat B Chiefmar 205 HV HV Alfa Laval 292 HV HV bearing seats: overall comparable hardness values, but higher surface hardness for Alfa Laval material can be improved by surface heat treatment gearing: same hardness range; gradient for Chiefmar material from tooth tip to base.

5 Steel Components: Bowl Spindle (part no ) Location of metallographic preparations on spindle components analyzed positions: cone and bearing seats location of the metallographic preparations Geometrical analysis of: dimensional and positional tolerances of the bearing seats and of the cone SD-coordinate measurement machine Results: more accuracy for Chiefmar spindle except for the cone position easy to fix problem Further analysis: material analysis microscopy hardness measurement (Vickers hardness and elastic indentation modulus) chemical analysis (EBMA* method) * EBMA: Electron Beam Microprobe Analysis Main Results of the Study: Steel Components C45 Worm Components: Dimensional and Positional Tolerances Materials Properties Gearing: Better tolerances and quality (tooth profiles and flank shapes as well as gear pitches) for Chiefmar than Alfa Laval, but finishing of the edges could be improved Bearing seats: positional tolerances were good for all parts Bearing seats: dimensional tolerances have to be improved for Chiefmar parts by better machining accuracy Material: heat treatable steel for Chiefmar and Alfa Laval with no remarkable differences (Alfa Laval material could be C60, but this is not sure; Chiefmar material is C45) Heat treatment: was not done for both manufacturers; however, a heat treatment process would improve the mechanical properties of the gearing and the bearing seats Mechanical properties: similar for the two manufacturers; could easily be improved at critical regions (bearing seats) by heat treatment like annealing or surface hardening C45 Spindle Components: Dimensional and Positional Tolerances Materials Properties Higher accuracy (in general) for the Chiefmar component The cone of the spindle has to be improved by better accuracy and manufacturing metrology during machining Material: similar material for Chiefmar worm and spindle component (C45), while Alfa Laval material could be lower alloyed (e.g. C40) No heat treatment of the materials for both manufacturers and no differences in microstructures Hardness of the bearing seats is slightly higher for Alfa Laval components Heat treatment of bearing seats could improve the mechanical properties in a large extent

6 Material Analysis for Seal Rings PA66 seal rings, results of the DSC analysis during heating Thermal analysis with the DSC method (differential scanning calorimetry): material was identified as polyamide 66 for Chiefmar and Alfa Laval (same melting temperatures) small differences in melting enthalpy and crystallization temperature there are differences in the composition or structure (cross linking) of the final polymers thermal durability slightly higher for Chiefmar material Polymer Components: Rectangular Rings and O-Rings Parts no /02/003, , , (rectangular rings) and (o-rings) Design sketch of Chiefmar rectangular ring: 8,0 8,0 Schematic setup of Shore A hardness tests on NRC rectangular rings: R 2, Ø 419,00 Geometrical analysis of: diameter of the rings patented optical measuring device cross section height and width measurement with laser scan micrometer Further analyses: mechanical properties hardness analysis (Shore A) and tensile testing standardized material analysis thermogravimetric analysis (TGA) extraction analysis Fourier transform infrared (FT-IR) spectroscopy Results geometry: good analogy between Chiefmar and Alfa Laval rectangular rings and o-rings hardness: hardness differences are small (negligible) no hardness influence on operation behavior

7 Mechanical Properties of Rectangular Rings and O-Rings Load-displacement diagram of tensile tests on NRC rectangular rings and o-rings load-displacement curve! Tensile test results statistical accuracy is not given due to low number of test specimens rectangular rings: trend to higher strength for Alfa Laval rings o-rings: difference in tensile strength is negligible Table: Results of tensile tests on NRC o-rings according to DIN remarks spec. no. load maximum load at 100 mm load at 200 mm load at 300 mm load at 400 mm (N) (N) (N) (N) (N) 001-O-CH max. elongation 002-O-AL max. elongation Chemical Composition of NRC Rings Superposition of FT-IRspectroscopies of the pyrolyzates of Chiefmar (blue) and Alfa Laval (red) rectangular rings Remark: Only one Chiefmar ring and one from Alfa Laval were analyzed due to high costs of the analysis! Consistent ingredients of the pyrolyzates of extractabie elements: butadiene and acrylonitrile Material analysis of nitrile rubber compound (NRC) for rectangular rings: thermogravimetry discovers larger fraction of elastomers for Alfa Laval material extraction and subsequent FT-IR spectroscopy yield the chemicals used for plastification (plastisizers) differences in the chemical composition of the plastisizers materials are quite similar, but with some differences in chemical composition and mass fractions of polymers, plastisizers and fillers

8 PA66 Seal Rings: Main Results of the Study: Polymer Components Dimensional and Positional Tolerances Manufacturing Process Materials Properties Quality of dimensional tolerances is the same for the two manufacturers (could be improved) Quality of the cross section shape could be improved for both manufacturers; this could be achieved by more remaining (cooling) time of the component in the die after injection moulding Die is different with respect to number of injection gates; this means that the manufacturing process should be optimized in terms of polymer mass temperature, die temperature and mould release agent that are used Hardness: higher for Chiefmar components, and thereby, the elastic modulus is higher as well Thermal behaviour (melting and solidification): shows that PA66 was used by both manufacturers; thermal durability is higher for the Chiefmar material (indicates that the molecular arrangement of the polymer is different due to different manufacturing parameters) NRC Rectangular Rings and O-Rings: Dimensional and Positional Tolerances Mechanical Properties Material Composition (analysis of 2 rings only!) Geometry and dimensions of the various rings are comparable for Chiefmar and Alfa Laval Differences in the dimensions of the rectangular ring cross sections in the region of mm Hardness: Measurement by Shore A showed same hardness for both manufacturers Tensile strength: difficult measurements due to limited number of test components; almost no difference in strength (with a small trend to higher values for Alfa Laval NRC rings) Thermal decomposition analysis: mass fractions of volatile constituents, polymeric fractions, carbon and ash filler material similar with slightly larger fractions of elastomers for Alfa Laval (5 wt.% more) and filler material for Chiefmar (2 wt.% more) Elemental analysis (spectroscopy) of extractable elements: rather similar materials of the two manufacturers with differences in chemical composition of the plasticizers (diluents) Summary and Conclusions Differences between Chiefmar and Alfa Laval components are small, both for polymer and steel components Chiefmar steel components have similar material like Alfa Laval components; material properties only differ slightly, but Chiefmar could improve their components significantly by additional heat treatment at critical positions (like bearing seats) The accuracy of the steel components is in general comparable; however, a better attention on manufacturing metrology (e.g., length measurements) will improve quality and lead to better overall performance Dimensional and mechanical properties of the polymer parts are very similar between the two manufacturers (higher hardness of the Chiefmar PA66, higher strength of the Alfa Laval NRC) For the seal rings, optimization of the manufacturing process would increase component properties and accuracy (e.g., better cooling after manufacturing) For the NRC material (rectangular rings and O-rings), there are differences in chemical composition; larger fractions of elastomers could lead to better tensile strength of the Alfa Laval rings; however, the true influence of different polymers and plastisizers (or diluents) in the NRC materials cannot be appointed for sure, because the composition of rubber compounds is complex All measurements in this study were made on new polymer and steel components from Chiefmar and Alfa Laval. Therefore, statistical evidence of the results is not possible. If customers would return damaged parts, failure analysis could lead to better understanding of specific application-oriented problems and improvement of the component design and manufacturing. sales@chiefmar.com Chiefmar s.r.l. Via G. Adamoli, Genova - Italy - ph fax