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  • NDT for Aerospace Coatings from Poeton
    Magnetic Flaw Detection Dye Penetrant Inspection Etch Inspection Hardness Testing and Optical Microscopy The high level of staff qualification and equipment standards ensures full compliance to prime contractor specifications on site and without the delays associated with using an outside service Magnetic Particle Inspection MPI or Magnetic Flaw Detection MFD NDT for detection of surface and sub surface imperfections on ferromagnetic materials including materials that have been treated with a non magnetic coating up to 50 microns 0 002 in thickness Liquid Penetrant Inspection LPI or Penetrant Flaw Detection PFD NDT utilising fluorescent techniques for the detection of surface imperfections and conditions on all materials regardless of their mechanical or material properties such as metals plastics and composites Etch Inspection NDT used for detecting grinding abuse particularly in Hard Chrome Plating The NDT technique involves a sequence of acid etches which highlight the soft or hard phases produced by poor and inconsistent grinding The parts are inspected in natural light the etch revealing the defects as white areas Heat Treatment Poeton have a wide range of fully calibrated ovens for the precise heat treatment sequences specified for stress relieving and de embrittlement of critical aerospace and defence parts This includes pre and post treatment of parts that are being chrome plated cadmium plated or treated by any process that might bring the risk of hydrogen embrittlement We can inspect parts up to 3 meters so that we can meet the volume and length demands of most aerospace and defence components We also have a full technical support laboratory with Optical and Scanning Electron Microscopy Metallography Atomic Absorption Spectroscopy Wear and Corrosion Testing Please see our Technical Assistance Section for additional information Aerospace Defence Medical Healthcare Energy Power Generation Automotive Chemical Oil and Gas Food Drink Equipment Electronics Telecoms General Engineering

    Original URL path: http://www.poeton.co.uk/w1/aerospace_ndt_details.htm (2016-02-12)
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  • Anodising
    can produce coatings up to 150µ thick and is ideal as a thermal barrier Note that only 50 of the coating grows outwards see above Surface finish and coverage It is important that the alloy surface be as smooth as possible before anodising The subsequent increase in roughness after anodizing depends on the alloy the purest giving the smoothest coatings E g on 6082 a 50µ coating will increase an original value of 0 2µ Ra to 0 4µ Ra In terms of coverage with the Apticote 300N process Poeton can successfully anodise down blind holes and along the inside of tubes to a depth equal to 10 X diameter A small area is left uncoated at the electrical contact mounting points Sharp corners give problems since the coating grows in two orthogonal directions and tends to crack All corners should therefore be radiused for best results Hardness The coating is essentially alumina with a compositional hardness of over 2500Hv Vickers Hardness But anodised layers have an open structure so that the measured micro hardness is typically 400 to 500Hv 25 or 50g load The purest alloys give the highest hardness and wear resistance since alloying elements like copper and silicon cause additional porosity in the layer Poeton Apticote 300M is softer around 300Hv deliberately so It is designed for more ductility and thickness as a thermal or electrical barrier Corrosion resistance Hard anodizing on the purest alloys like 6082 gives moderate corrosion protection further enhanced by di chromate sealing Coating salt mist endurance Sulphuric anodised 300 hrs Hard anodised HA 400 hrs HA di chromate seal 600 hrs For the best corrosion protection with anodised coatings 1000 hrs consult our web pages on anodic polymer composites Apticote 350 Wear resistance Apticote 300N hard anodising is ideal for low stress abrasion situations where the inherent hardness of the alumina coating can resist wear from a wide range of products provided the loads are light The coating can provide wear resistance superior to that of hardened steel so that it is suitable for use with abrasive food and pharmaceutical products Machining Hard anodised coatings can be honed ground or lapped using light cuts If tolerances are wide polishing by hand can remove superficial roughness and bring back the original finish When tolerances are tight grinding or honing with fine SiC abrasive is recommended For polishing and lapping use Boron Carbide abrasive in heavy oil or petroleum jelly With an alloy like 6082 a finish of 0 05µ Ra is achievable Process control Regardless of the process type anodising requires strict controls on the bath parameters including composition build up of dissolved metals temperature and pH There is also a tight specification on the electrical parameters the DC voltage it s ramp up and ramp down the allowable AC ripple the anodising time and the maximum time period parts can be in the bath before anodising is commenced Any of the electrical parameters can vary according to the aluminium alloy being processed

    Original URL path: http://www.poeton.co.uk/w1/hard-anodising.htm (2016-02-12)
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  • Chrome plating
    Tool slideways Compressor cylinders Valves and pumps Thickness The minimum thickness for a viable wear resistant coating of hard chrome plate is 12 5 0 0005 inch a deposit that will be smooth and bright and should require no post finishing For arduous high load applications layers up to 250 0 010 inch might be required post ground to a pre determined final size With thin coatings designers can plan for an accurate coating thickness with even distribution for instance adding up 25 to the diameter of a shaft For thicker coatings the part must be prepared under size plated to over size and ground back to its required dimensions Variations Standard hard chrome plate Poeton Apticote 100N is naturally micro cracked a network of ultra fine cracks less than 1 wide in a crazy paving pattern They are an inevitable consequence of stresses in the coating and are beneficial to lubricant retention on the surface If the substrate requires exceptional corrosion protection one option is to apply a thin dense chrome Poeton Apticote 100C where the electrolyte and temperature are adjusted to produce a crack free deposit It is thinner and softer than conventional hard chrome For additional wear protection conventional hard chrome can then be applied on top Alternatively the hard chrome plate can be undercoated with a thick layer of electrolytic nickel providing a reliable corrosion barrier Note that chrome plate and nickel plate are not sacrificial coatings like zinc or cadmium if they are breached substrate corrosion can occur unchecked Poeton Precision Hard Chrome Plating is a specialised variant where the deposit thickness and coverage is controlled to close tolerances It requires special anodes cathode extensions and jigging and eliminates the need for final grinding The subsequent coating is harder has superior substrate bonding gives more wear resistance and requires shorter production times Flash hard chrome plating is a thinner variant about 10 with limited covering power applied only for mild wear situations Substrates Hard chrome plating can be applied to cast iron all grades of steel most aluminium alloys Non ferrous metals such as copper and bronze are ideal substrates Substrates can be cast rolled or extruded However materials with near surface porosity or imperfections should be avoided Plating on hardened steels is more difficult and isolated work hardened areas can cause irregular coating High Tensile Steels Most steels are readily electroplated with chromium and require no heat treatment But heat treatment of high strength steels after plating may be required to minimise the effect of hydrogen embrittlement and or any reduction in fatigue strength Surface finish The component finish prior to plating should ideally be 0 2 Ra ground or 0 8 Ra turned although polished surfaces can be successfully plated Rougher surfaces may cause pitting in the coating In general the coating finish will be slightly rougher than that of the original substrate Hard chrome can be polished to a high finish 0 02 Ra or better Process control Hard chrome plate is

    Original URL path: http://www.poeton.co.uk/chromium.htm (2016-02-12)
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  • Non stick and low friction polymer coatings
    good release FDA compliant Uses Apticote 200 polymer coatings are used in a wide variety of industries including Pharmaceutical Packaging Food Chemical Moulding Automotive Plastics Tobacco By understanding the problem and specifying the correct Apticote 200 grade Poeton can boast a long list of successes 5 times life of tyre moulding tools Elimination of sticking and plucking in delicate medical implants 6 times reduced wear in plastic moulding tools Low wear and scuffing on automotive piston skirts Complete non stick in biscuit and bread making machines 3 times reduced wear in tobacco handling equipment Corrosion protection and low friction handling chemicals 10 times life in high temperature packaging operations Reduced sticking and ink deposit build up in printing applications Eliminates deposit build up on rollers processing plastic film Substrates Apticote 200 coatings can be applied to a range of metallic substrates In practise the curing temperature is critical so that the low temperature cure with A200B or A200L is recommended for temper sensitive tool steels A200C is best suited for stainless steel substrates Thickness Apticote 200 coatings are typically 25µ thick with a variation around 5µ and it is unusual for an application to require any tight tolerances The clear A200C is thinner 5µ and A200N can be applied thicker 50µ for corrosion protection Uniformity and coverage Coverage on flat surfaces is even but the spraying process is line of site so that bores and re entrant features are difficult to cover For such complex parts electrostatic spraying is best The coverage of sharp corners depends on the spray technique electrostatic spraying providing good replication In contrast wet spraying can sometimes lead to only thin coverage on corners Surface finish The melt flow polymers tend to give the smoothest finish whereas the sprayed and cured products sometimes show an orange peel surface effect Typically a thick polymer coating will have a surface roughness up to 2µ Ra Colour The colour varies with the type of polymer some products being clear A200C Whilst the colour of any one polymer will be consistent there will be subtle variations so that colour matching cannot be guaranteed Post finishing Polymer coatings are used as sprayed They should not be polished or finished in any way Cleaning Poeton will advise on the appropriate chemicals to be used for in service clean down depending on the coating product combination Curing temperature After deposition the parts are baked to melt flow or cross link the polymer depending on the type This obviously has a bearing on the substrate Poeton can advise on what coating is best for your substrate material and application 200B 2607 C to 345 C 200C 340 C 200E 400 C 200G 400 C 200L 220 C to 345 C 200N 370 C In service temperature The limiting operating temperatures of the Apticote 200 coatings are 200B 260 C 200C 205 C 200E 260 C 200G 205 C 200L 260 C 200N 200 C The lower operating temperature limit is around 70 C Sliding

    Original URL path: http://www.poeton.co.uk/polymers.htm (2016-02-12)
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  • Electroless Nickel
    as the bath ages Best results as with the Apticote 400 process maintaining a compressive stress throughout the bath life is achieved by automated monitoring of the bath chemistry and continuous metered makeup additions rather than periodic volume additions Hardness As plated medium phosphorous Electroless Nickel has a hardness of 500 550 VPN This can be increased by heat treatment which precipitates a Ni 3 P dispersion in the nickel matrix to values up to 1000 VPN thereby increasing the wear resistance The optimum heat treatment is 1 hour at 400 C The low phosphorous variety is harder as plated 700 750 VPN The high phosphorous version is not usually heat treated it is left as plated for its superior corrosion protection Colour As plated the coating has a silver colour Heat treatment at 400 o C to harden the coating will give it a slight straw coloured hue Corrosion Electroless Nickel is a barrier coating preventing a corroding media attacking a vulnerable substrate It is not a sacrificial coating like cadmium or zinc Corrosion protection is greatly reliant on the integrity of the coating being free from cracks and porosity and with a residual compressive stress In the Apticote 400 process this advantageous compressive stress is maintained throughout the bath life by continuous monitoring and chemical additions Some comparative salt mist endurance results Mild steel 20 hours Phosphated mild steel 220 hours Electroless nickel on mild steel with uncontrolled bath chemistry 250 hours Medium phosphorous electroless nickel on mild steel Apticote 400N 400 hours High phosphorous electroless nickel on mild steel Apticote 400P 600 hours Medium phosphorous electroless nickel with graded structure Apticote 400D 1000 hours Wear resistance Electroless Nickel provides good low stress abrasion resistance as illustrated in the Taber Abrasion SiC wheels at 100g load results below relative wear rates low is best Stainless steel 50 Standard electroless nickel 15 Apticote 400N as plated 10 Apticote 400N heat treated to 1000Hv at 400 C 4 Substrates Electroless Nickel can be deposited on most metals and alloys including steels copper alloys aluminium alloys and titanium Deposition on non conductors such as plastics requires an ionic palladium activator Machining Electroless nickel is not usually machined since it provides even coverage However for precision bores it can be honed and for reflective surfaces such as mirrors it can be super finished or highly polished Surface finish Electroless nickel replicates the substrate texture so that dictates the surface finish in most applications If it is applied to a highly polished surface the coating will retain its own fine texture typically 0 1µ Ra Physical properties Poeton Apticote 400N Electroless Nickel has the following properties Density 7 9 gm cc Melting point 890 C Electrical resistivity 60 75 microhm cm Thermal conductivity 0 012 cal cm sec C Coef of thermal expansion 3x10 6 cm cm C Reflectivity 50 that of silver Mechanical properties The loss in fatigue strength of a high tensile steel component after Electroless Nickel plating is less than

    Original URL path: http://www.poeton.co.uk/electroless-nickel.htm (2016-02-12)
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  • Thermal Spray coatings
    wide variety of problems including Low stress abrasive wear Occurring in industries like textiles plastics and food where micro particles in the product cause abrasion of machine parts for instance a textile guide The best solution is usually a plasma sprayed ceramic like chromium oxide High stress abrasive wear Occurring in pumps valves conveyors etc where aggressive debris or product is heavily loaded against operating surfaces Only the toughest and hardest high energy thermal sprayed coatings should be specified Fretting and surface fatigue This requires tough rather than hard coatings with materials like nickel based alloys that resist cracking and oxidation both characteristics of fretting fatigue Applications include cam followers rocker arms expansion joints seals and press fit spacers Erosion Erosion either by impinging particles or fluids perhaps with cavitation is best resisted by tough rather than hard coatings Applications include exhaust fan blades and seats turbine nozzles and dust collectors Salvage Parts that have been damaged worn or eroded can reclaimed by sprayed coatings The damaged area is cleaned up blasted and then coated with new material oversize before being machined or ground back to size The coating must in general match the substrate with regard to the composition and hardness including their required machining or grinding characteristics Corrosion and stress corrosion Nickel chrome or cobalt based spray coatings are available for protection usually sealed to close any residual porosity On high strength steel or aluminium substrates a corrosion resistant coating sometimes followed by shot peening can combat stress corrosion and eliminate cracking failures Thermal barriers Ceramic coatings such as alumina MCrAlY or ittria stabilised zirconia provide low conductivity and an oxygen diffusion barrier protecting vulnerable substrates Applications include piston crowns rocket nozzles missile nose cones and carburising boxes Electrical Conductivity sprayed metals like copper for lightening arrestor and ground connectors Resistivity dense pore free sprayed ceramics for the highest dielectric constant for insulation applications Including heater tubes soldering tips and electronic parts Shielding sprayed coating to absorb and earth stray RF induction and others to shield against gamma rays or thermal neutrons Applications including instrument assemblies and missile systems Bedding in The classic application of thermal spray coatings is for turbine stators where an abradable coating like Nickel graphite is applied Abrasive coatings on the turbine blade tips then cut the stator surface creating the perfect dimensional match with minimum blade stator clearance Efficiency and costs Powder costs are an important element of the processing economics so spray efficiency is a crucial aspect To this end Poeton employ a Sulzer Metco TriplexPro 200 Robot Plasma Spraying System offering the ultimate in spraying performance Additionally our Sulzer Metco MultiCoat High Performance Thermal Spray Controller can simultaneously control up to four thermal spray processes from a single consol Plasma spray single triple cathode guns HVOF spray gas and liquid fuel Combustion powder spray Combustion wire spray Quality control Quality control covers four main properties overseen by the Poeton laboratory the thickness porosity substrate bonding and coating structure Central to this

    Original URL path: http://www.poeton.co.uk/thermalspray.htm (2016-02-12)
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  • Cadmium Plating
    applied by electro deposition from cyanide or acid solutions in barrels or vats It can also be applied by mechanical plating vacuum deposition and metal spraying but generally only electroplated cadmium is of commercial importance Cadmium is a by product of Zinc production and it was not until the 1920 s that electroplating of cadmium became widely used as a protective coating Today the Western World annual consumption of cadmium for coatings is about 1000 tones which is a relatively small proportion of total cadmium consumption Over 90 per cent of all Cadmium coatings are deposited by electroplating Coating Properties Cadmium as an electroplated metallic coating has the following advantages It provides sacrificial protection to the underlying steel as described under background The atmospheric corrosion protection of cadmium is predictable and is proportional to the thickness of the coating Cadmium electroplating is normally specified with minimum thickness between 5 and 25 microns depending on the severity of atmosphere Cadmium has good resistance to rural and marine atmospheres in alkaline conditions and detergents It proves an effective barrier to prevent the galvanic bimetallic reaction between steel and aluminium such as where aircraft undercarriage and weaponry mechanisms are fixed to aluminium framework Undercutting of threads on nuts and bolts is not necessary The coating has a low coefficient of friction which reduces the tightening torque and allows repetitive dismantling Cadmium corrosion products have small particle volume and are adherent so valves and delicate mechanisms will not likely to be jammed with debris Thin Cadmium coatings are appropriate on threaded components where dimensional tolerances must be maintained Cadmium can be formed as easily as the substrate It can easily be soldered without the use of corrosive fluxes and has a lower electrical contact resistance than zinc coated steel These are important properties for the electrical and electronics industry Cadmium can have an attractive polishable silvery finish The Cadmium plating process can be applied to all ferrous materials including malleable iron and to brass and aluminium The process can enable a high efficiency throwing power i e the recesses are more readily coated with a reasonably even deposit Cadmium plated steel is readily adhesive bonded Chromating directly after electroplating can increase the corrosion resistance of the coating and greatly extend the coating life by preventing the sacrificial process from commencing until in service High Tensile Steels Most steels are readily electroplated with cadmium and require no heat treatment either for stress relief or for avoidance of embrittlement due to hydrogen entrapped during the process Base metals of tensile strength above 1100 MPa should not be electroplated with cadmium by conventional methods Instead specialised pre treatment and coating procedures have to be used Apticote 900L along with stress relief and de embrittlement by way of specific heat treatment cycles Apticote 900L a Low Hydrogen Embrittlement LHE form of cadmium plating LHE Cadmium Plating uses a higher current density with no brighteners and the bath chemistry is modified to produce a more porous structure duller After

    Original URL path: http://www.poeton.co.uk/w1/cadmium-plating.htm (2016-02-12)
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  • Specifying an Engineering Coating
    prohibited pre treatment steps such as acid etching embrittlement concerns or aggressive roughening by blasting contamination distortion concerns Indicate its function For large parts the weight 2 Define your coating needs Show on the drawing the area that must be coated Indicate if the part can or must be coated all over or if there are some areas that MUST remain uncoated Remember that in most cases it is more expensive to mask such areas than to coat the part all over In particular indicate internal areas or bores that must be coated where special processing fixtures may be needed to coat such areas when access may be restricted Consult the supplier on the practicalities Indicate where the part can be held on a jig either for support and or for the provision of a sound electrical contact Remember that such a holding point may show a witness mark where the coating is thinner or not present If it is a heavy part indicate the allowed lifting points Show the required coating thickness and a tolerance band If the requirement is to coat the part to attain a specified finished size then specify that size and its tolerance Remember that the coating process itself will have its own tolerance band consult the supplier so that such tolerances are ADDITIVE with the incoming size tolerance Indicate any features such as holes or threads that need to be protected have special tolerances or may trap processing chemicals Show any requirements for the as coated surface finish that is assuming that no further finishing operation grinding polishing etc is planned If colour or appearance matching is required specify the standards Remember that colour matching may be expensive and difficult with an engineering coating If a finishing operation is specified as part of the coating service e g grinding then provide details of the required final size and tolerance as well as the required surface finish and tolerance For sensitive parts agree the required pre coating stress relieving and post coating de embrittlement heat treatment times and temperatures Agree any requirements for Quality Control testing or sampling either non destructively on finished parts or destructively on sacrificial parts or test coupons Properties such as hardness thickness surface finish etc can be within this requirement 3 Define the commercial issues Provide a clear purchase order Include clear references to the supplier s quotation paperwork to repeat orders and to individuals in the supplier s company who have technical knowledge of your application Show the number of parts to be processed Wherever possible agree with the supplier sensible batch sizes that fit efficiently with rates of processing and the number of parts that can jigged and coated simultaneously Agree on your scheduling Ensure that delivery time to the supplier allows him to process your parts to meet your final deadline requirements The coating step is often the final step in the manufacturing route a point where impossible demands to catch up on slipping time schedules are

    Original URL path: http://www.poeton.co.uk/w1/specifying.htm (2016-02-12)
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web-archive-uk.com, 2016-10-23