1.9.1.2-alcro - arc sprayed iron-chrome-aluminum wire
TRANSCRIPT
File: 1.9.1.2-ALCROIssue: Q10507
Supersedes: Q10326
TAFA ARC SPRAY IRON-CHROME-ALUMINUM WIRE - ALCROMaterial Review:
Made exclusively for arc spraying. This material produces coatings which highly resist corrosive gases in boileratmospheres such as vanadium and sulfur and oxidation temperatures up to 1600°F. A coating of this material can alsobe used to resist heat and prevent oxidation scaling of conventional low alloy steels. The coating is machinable.
The material should be sprayed with Praxair and TAFA's special arc spray boiler coating system.
The ALCRO material is prealloyed, not like composite powders which when plasma sprayed produce significant amountsof dust leading to coating inclusions and less density. The composite powder also produces cells of different materials(non-homogeneous) which may lead to localized corrosion and/or spalling.
CAUTION: All Praxair and TAFA wires have been optimized for arc spraying. Use of alternate wiresUsually causes problems such as excessive tip wear, spitting and feeding problems. We onlyrecommend Praxair andTAFA certified wires.
Application Review:
ALCRO is a solid wire drawn to the FeCrAl composition listed below. This material contains chromium and aluminum forcorrosion resistance and superior bond strength.
Solid wires are much easier to work with both from a feeding and spraying perspective. ALCRO coatings produce highlymachinable coatings that can be machined faster than other thermal spray coatings (generally in the 250 to 550 surfacefeet per minute range). ALCRO coatings feather into edges or base metals without noticeable parting lines. Fine finishes(12-32 RMS) can be achieved using the correct machining parameters, and spraying techniques. ALCRO is a selfbonding material with high bond strengths. Coatings can be built up thicker than .150" per side without much stress buildup. This material/coating is ideally suited to repair mis-machined parts, shafts, bearing fit areas, dies, rolls and journals.This coating is recommended for those applications that require a machine finish to restore parts having most commonsteels as base materials. Common Steels such as 1018, 4140 carbon steel, 200, 300, and 400 series stainless steels,most tools steels and cast iron.
This material is not as corrosion resistant as TAFALOY 45CT® but in certain less aggressive environments may provemore cost effective. It produces superior adhesive bond strengths (7000+ psi) when sprayed with Praxair and TAFA'sspecially designed arc spray system. Praxair and TAFA's system with ALCRO produces cooler, extremely low thermalshock coatings which can be used for patching older type plasma coatings more effectively than plasma or gas wireguns.
This material, when sprayed with nitrogen, produces an extremely desne, high conductivity, low oxide content coatingwhich could be used for on-site spraying of resistive heater elements or strips on ceramics.
1.9.1.2-ALCRO
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Composition:
Aluminum 4.2 - 5.3 percent
Silicon 0.65 maximum
Chromium 20.5 - 23.5 percent
Iron Balance
Coating Physical Properties
Wire Size 1/16" (1.6 mm)
Deposit Efficiency 82 percent *
Melting Point 2770 F (1520°C)
Bond Strength 7000 psi (53.6 MPa)
Coating Texture 300-350 microinches AA
Machrohardness 230 Knoop100 (Rb 88)
Coating Density 7.1 gm/cc
Coating Weight 0.0375 lbs/ft2/mil
Porosity Less than 1 percent
Finish, machined: ground:
FairGood
Resistance: 783 ohms/mil/ft2 (68°F)
Coefficient of Expansion: 14.1x10-6 in/in/°C (20-800°C)
Spraying:
Spray Rate 11 lbs/hr/100 amps (5 kg/hr/100 amps)
Coverage (wire consumption) 0.8 oz/ft2/0.001" (0.98 kg/m2/100 micron)
Spray Pattern****(approximate 8" standoff) Cross Nozzle/Positioner - 1" (2.5 cm) vertical height x 1-3/4" (4.4 cm) widthSlot Nozzle/Positioner - 2" (5 cm) vertical height x 1" (2.5 cm) width
Length of wire per lb 104 ft (1/16")
* Depends on gas pressure and standoff
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Spraying Procedure:
Coating Type
Normal8830/8835
Arc Jet8830/8835
Arc Jet9000 9000
Atomizing Air Pressure:PrimarySecondary
50c
-- --50c
40c60c
60c60c
-- --Nozzle Cap Blue * Green GreenNozzle/Positioner Short Cross ** Long Cross Long CrossArc Load Voltsa 29-30 29-30 30-32 30-32Ampsb 50-300 50-300 50-300 50-300Standoff Inches 5-7 5-8 5-8 5-7Thickness/Pass-mils 5 5 5 5Texture-microinches aa 200-350 150-250 150-250 200-350
Using excessive voltage reduces quality of coating. Voltage should be adjusted to give minimum noise andsmooth arc operation. Excessive voltage causes larger particles and poor spray pattern. Too low a voltagewill cause popping.
Be sure not to overheat substrate even if this means stopping to allow cooling, use air jet cooling if greaterspeed is required. Note that on some applications where preheating is tolerable, preheating work to 300°Fcan improve bond and deposit efficiency.
NOTE: Standard air caps and positioners can be used in 8830 or 9000 systems.
* P/N 450729 8830 Arc Jet Air Cap** P/N 620074 Arc Jet Modified Short Cross (8830 & 9000)
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a When using power lead extensions other than the normal 12 foot furnished, the voltage must be increase by approximately 3.4 volts per 50 ft. of extension; i.e., add 3.4 volts to the recommendedvoltage setting for a given wire if the extension is increased to a 50 foot length.
b Can vary between 50-300 depending on size of workpiece and traverse speed.c For finer finish, raise air pressure at point of finish.
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Finishing:
ALCRO is usually finished by machining or grinding. Machining gives a fair finish and grinding gives a goodfinish.
Hazards:
Chrome is under investigation in the welding industry as a toxic substance. Full respiratory protection shouldbe used when spraying this material.
Observe normal spraying practices, respiratory protection and proper air flow pattern advised. See AWSPublication AWS C2.1-73, "Recommended Safe Practices for Thermal Spraying" on general spray practicesand AWS TSS-85, "Thermal Spraying, Practice, Theory and Application". Thermal spraying is a completelysafe process when performed in accordance with proper safety measures. Become familiar with localsafety regulations before starting spray operations. DO NOT operate your spraying equipment or use thespray material supplied before you have thoroughly read the TAFA Instruction Manual.
DISREGARDING THESE INSTRUCTIONS MAY BE DANGEROUS TO YOUR HEALTH.
The Information provided herein is believed to be accurate and reliable; however, results may vary withworkpiece preparation and operator technique. TAFA warrants only that the wires are free of defects inmaterial and workmanship. No other warranty is expressed or implied.
Copyright 2000 Praxair Technology, Inc. All rights reserved
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Praxair, the Flowing Airstream design and Making our planet moreproductive are trademarks or registered trademarks of PraxairTechnology, Inc. in the United States and/or other countries.
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TAFA is constantly improving its products, therefore specifications aresubject to change without notice
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