What Is Plasma Transferred Arc Welding (PTAW)?
1/12/15jsWhat is Plasma Transferred Arc Welding (PTAW)?Abstract:Are you looking for a more economical way to overlay your components with a metallurgical bonded,high hardness, corrosion resistant, or high-wear metal matrix material? Plasma Transferred Arc Welding(PTAW) may be the solution for you with up to 20% savings over laser cladding and other solutions. Thispaper will provide a better understanding of this process and how it can benefit your company andapplications.Discussion:What exactly is PTAW? Plasma Transferred Arc Welding is a thermal process for applying wear andcorrosion resistant layers on surfaces of metallic materials. It is a versatile method of depositing highquality metallurgically fused deposits on a wide range of base materials from carbon steel to exotics likenon-mag super austenitic and nickel alloys. Soft alloys, medium and high hardness materials, andcarbide composites can be used to achieve diverse properties such as improved mechanical strength,wear resistance, galling resistance, and corrosion resistance.The welding process employs a constricted high-energy plasma arc between a non-consumableelectrode and the base material, creating a molten weld pool. Filler material is introduced in either awire form, which is fed into the back of the weld pool, or in powder form, which is fed through the torchand introduced to the welding arc above the weld pool. This process produces a metallurgically bondedoverlay that has better fusion and corrosion properties than mechanically bonded processes.Like laser, PTAW especially excels in powder alloys that are too hard to draw into wire, Cobalt 190, forexample, and metal matrix composites where an extremely hard material, such as tungsten carbide, isapplied together with a binder material like nickel. In most applications, the PTAW process is able toapply the same materials at the same quality as laser, at a significant cost savings due to PTAW’sreduced operating and ownership costs.When compared to GTAW overlays, PTAW’s lower heat input allows the process to achieve the requiredoverlay properties in a thinner layer, resulting in lower costs. Additionally, alloys that are very expensivein wire form, like Cobalt #6, are sold at a 50% discount in the powder form, again giving PTAW theeconomic advantage.PTAW is often times more economical than even low tech processes like cored wire GMAW and sprayand fused thermal spray. The capability of producing a low dilution, porosity free, thin overlay allowsthe PTAW process to achieve a higher quality product using much less material and with drastically lessheat input into the base material.
Equipment:1. PTAW Torcha. Cathode - Tungsten Electrode. Conducts current for both the main and pilot arcs.Electrode (-)b. Anode – Constricts welding arc and Plasma Gas through the orifice, delivers powder tothe welding arc, maintains the pilot arc.c. Shielding Nozzle – Directs shielding gas to the weld.2. Power Supplya. Main Arc Power Supply – Provides power for the transferred welding arc between thetungsten electrode and base metal.b. Pilot Arc Power Supply – Provides power for the non-transferred pilot arc which enableseasier ignition of the main welding arc. This arc is usually on at all times and existsbetween the tungsten electrode and anode.3. Gas Supplya. Shielding Gas –Displaces the ambient atmosphere and protects both the welding arcand molten weld pool.b. Plasma Gas – Ionized at the electrode and the plasma is constricted as it is forcedthrough the anode orifice.c. Powder Carrying Gas – Transports the powder from the powder feeder through thetorch.4. Automationa. Not required, as PTAW can be applied with a handheld torch. However, PTAW, like allwelding processes, benefits greatly from precise motion, and parameter control.Plasma Coatings has two fully automated PTAW systems
Features: The electrode is protected inside the anode, allowing powder to be used as a filler materialwithout tungsten degradation. Powder filler material allows PTAW to apply very hard alloys thatcannot be drawn into a wire (Stellite 190) as well as metal matrix composite materials (tungstencarbide in a NiSiCr matrix). Custom blended alloys can also be developed and tested veryquickly and inexpensively.Since PTAW utilizes a constricted, columnar welding arc; the heat input is highly localized. Thisallows full fusion of the overlay material, while introducing minimum heat into the part. Heatinputs comparable to laser are achievable with careful parameter optimization and control.The low heat input possible allows PTAW to be very effective at hard-banding of nonmagneticalloys. Critical wear bands for MWD tools made from P570, P550, Inconel and 17-4 have allbeen successfully overlaid with tungsten carbide and have passed stringent magnetization tests.Applications: Hard Surfacingo PTAW is well suited to apply hard alloys for wear resistance. Stellite, Colmonoy,Hastelloy, and Tungsten Carbide can all be successfully applied with PTAW.Corrosion Resistant Overlayso The localize heat input characteristics of PTAW allow corrosion resistant alloys to beapplied with very little dilution into the base material. PTAW can achieve subseachemistry requirements of 5% Fe in as little as 0.040” of overlay thickness.Industries / Componentso Non-Mag Down Hole Tools Drill Collars, Wear Bands for MWDs, Flex Ponies etc.o Down Hole Components Mud Motor Bearings, Stabilizers, Topsubs, Piston SubsFlow Restrictors, Drill Bitsetc.o Flow Control Valve Bores, Gates, Seats, Seat Pockets, Ring Grooves, Valve Stems etc o Power Generation Turbine Blades, Shafts, Bearing Surfaces, etc.Riser Equipmento Pins, Boxes, etc.
Examples of PTAW Overlayed Components:Figure 1. Nitronic 50 Overlayed with Stellite 6 crack free.Figure 2. Rock Bit Journal Overlayed with Stellite 190 Crack Free
Figure 3. Helical Blade Stabilizer with Tungsten Carbide OverlayFigure 4. PTAW in Action
Conclusion:The PTAW process produces overlays that excel in extreme environments. It is used to improve variouscomponents in a variety of industries, including Oil and Gas, where wear, erosion, abrasion andcorrosion are concerns. Many surface properties needed for special applications can be economicallyproduced by PTA welding. PTAW is an exciting technology that allows Plasma Coatings to improve thesurface of components without significantly degrading the properties of the original base material. It isbest to work with Plasma Coatings to establish a mutual understanding of the requirements andapplication for PTAW.
the welding arc, maintains the pilot arc. c. Shielding Nozzle – Directs shielding gas to the weld. 2. Power Supply a. Main Arc Power Supply – Provides power for the transferred welding arc between the tungsten electro
The plasma arc cutting and gouging processes use this plasma to transfer an electrical arc to the workpiece. The metal to be cut or removed is melted by the heat of the arc and then blown away. While the goal of plasma arc cutting is the separation of the material, plasma arc gouging is used to remove metals to a controlled depth and width.
Plasma Etching Page 2 OUTLINE Introduction Plasma Etching Metrics – Isotropic, Anisotropic, Selectivity, Aspect Ratio, Etch Bias Plasma and Wet Etch Summary The Plasma State - Plasma composition, DC & RF Plasma Plasma Etching Processes - The principle of plasma etching, Etching Si and SiO2 with CF4
2.0 MagMate Cut25 Plasma 6 2.1 Fundamentals of Plasma Cutting 6 2.2 Process operation for transferred arc applications 7 3.0 Plasma cutting components 8 3.1 Plasma cutting power sources 8 3.2 Plasma cutting capacity 8 3.3 Plasma cutting torches (general) 8 3.4 Air supply 9 3.5 Process comparisons 9 3.6 Work return cable assembly 9
For Reference Only ARC 8D ARC 10D ARC 12D ARC 15D Dimensions And Specs 1 Recommended Enclosures ARC 8D 2 ARC 10D 2 ARC 12D 3 ARC 15D 3 . .65 cu.ft. .75 cu.ft. .85 cu.ft. Minimum SPL SQ ARC 10D2 ARC 10D4. 3 TOP NOTE: These woo
Principle of plasma cutting Plasma cutting is a thermal cutting process in which a plasma arc is constricted through a nozzle. The transferred arc, which occurs when electricity flows from the non-melting electrode (cathode) to the workpiece (anode), is used to cut electrically conductive materials. This is the most commonly used form of plasma .
A PLASMA ARC CAN CAUSE INJURY AND BURNS . Plasma arc can cut anything instantly. -Keep hand away from the torch tip when the plasma unit is on -Do not hold metal near the cutting path. -Never clean up the torch head when the plasma unit is on. PLASMA ARC RAYS CAN BURN SKIN AND EYE . Plasmas produce intense visible and invisible
Plasma Fundamentals - Outline 1. What is a plasma ? Temperature Debye shielding Plasma frequency 2. The edge of a plasma Sheath physics 3. How to ignite a plasma Ignition, Paschen curve Streamer RF-ignition 4. Transport in a plasma Particle motion Plasma
High Current Level Arc "Parallel Arc" An Arc Fault That Occurs at 75Amps and higher An Arc Fault That Occurs Line-Line or Line-Neutral Types Of Arcing Faults Low Current Level Arc "Series Arc" An arc fault at low levels down to 5 Amps An arc fault at a break or gap in a single conductor in series with a connected load
