PTA Welding and Overlays
Automated P.T.A. overlays
Our Plasma transferred Arc Welding capabilities are the overlay of external components to almost any size and shape, or internal bores down to as small as 2.25 inches in diameter.
The Taskmaster Plasma Transferred Arc Welding System is a precise, high energy, inert gas welding process. It produces a very high quality deposit offering optimal performance with minimal dilution or deformation of the base material. Unlike some thermal spray processes, which have a mechanical bond, PTA technology produces a metallurgical “welded” bond that is particularly effective in protection against corrosion, erosion, abrasion, and thermal shock.
A wide range of overlay alloys are available designed to suit practically any application. The system works with metal powders as overlay material, so almost any desired product can be applied. Examples are: chrome carbide, tungsten carbide, nickel or cobalt based powders, stainless steels, and future development of possible ceramic-based powders.
The accuracy in application and parameter control results in a dilution level of only 3 to 7%, compared to traditional welding processes which can dilute with the base metal by as much as 40%. The process results in a very narrow heat-affected zone, and with the low dilution rate, prevents undesired substrate changes that can enhance the alloy’s performance in manufacturing components. The Taskmaster PTA welding system can deposit metal alloys at rates of up to 20 lb/h, and is fitted with automated manipulation to handle different parts, even those with complex shapes and narrow tolerances.
In a competition with laser surfacing, the PTA technology offers much higher productivity, with comparable quality of deposits, and significantly lower costs.
Typical application areas of the PTA technology are equipment for mining, crushing, rolling, road building and tunneling, extruding screws, valves and seats, power generation, cutting tools (milling cutters, broaches, knifes), Process equipment in ceramics and cement production, plastic molds, forging dies, pulp and paper industry equipment, and agricultural equipment.
We have a broad capacity of PTA equipment, each which can be outfitted to do flat surfaces, external, or internal diameters:
Taskmaster PTA #1, semi automated linear PTA system
Taskmaster PTA #2, semi automated linear PTA system
Taskmaster PTA #3, semi automated linear PTA system
Taskmaster PTA #4, semi automated linear PTA system
Taskmaster PTA #5, Automated Tandem ABB Robotic Cell. 2 x 150Kg capacity robot manipulators.
Taskmaster PTA #6, Manual, hand held torch PTA system.
Taskmaster PTA #7, semi automated Mobile unit for On-site work.
32 foot long, Non-Magnetic Flex Collar. Hardbanding in tandem with two PTA”s. Application innovations that save you time.
Taskmaster PTA system set up on Internal application production
Bent housing, Tungsten carbide wear pad, overlaid via our PTA robotic Station.
Traditional WELDED overlays
GTAW ( tig ), GMAW ( mig ), and SMAW ( stick ) weld overlay materials, although not as high in performance as that of PTA, have made many advancements in recent years, and due to lower equipment set up costs are still in wide spread use in industry.
We have integrated the mig welding process with our custom designed Automation equipment to ensure highest quality results with predictable repeatability.
Many common alloys can be applied such as Aluminum Bronze, Chrome Carbide, Tungsten Carbide Composites, Nickel or Cobalt base, and Low alloy Manganese products.
Taskmaster can provide these services as a cost effective alternative to PTA hard facing when the application if better suited or more efficient utilizing these traditional means. On parts not economical to set up with automation ( small / Odd shaped ), We have the expertise to apply these products manually, so we can get into the most unusual places with a desired coating. Another option we commonly offer, is to use traditional welded overlays in conjunction with PTA to get full coverage on parts or in areas hard to reach by the automated PTA process.
Welded Aluminum Bronze coating on alloy Steel Part, coating finished at 1/4 inch thick.
Tungsten Carbide Composite Overlay Selections
Bearing application hardfaced with TM – 1000 enhanced PTA overlay
Specialty Non Mag PTA hard surfacing ‘TM-NM’
Traditionally, welding on non-magnetic steels is not recommended, however over the year’s different processes and procedures have been developed. These processes have had limited success for various reasons. The need to keep the base material below critical temperatures was one such challenge… some tried to do so using water cooling / quenching which creates a new set of problems. Material chemistry when molten, and reacting to the base material elements becoming slightly magnetic was the other major hurdle. In the past, people would simply put a magnet on the weld and if it didn’t stick they thought it was good… how far we have come!
At Taskmaster, we have combined our vast industry knowledge and years of R & D to develop a superior method combined with tailored materials to achieve industry leading results.
Our proprietary methods ensure base material temperatures are maintained in the desired range and heat input into the work piece is minimized. This results in less cracking, and reduces pre-mature material failure due to fatigue.
The following are highlights of Taskmaster Standard Non-mag PTA data (TM-NM):
Bonding Mechanism: metallurgical welded bond – can be verified using ultrasonic testing
Matrix alloy: proprietary nickel based nonmagnetic corrosion resistant alloy
Hardness: 30-35 HRC – tough and impact resistant
Tungsten Carbide particles: extreme wear and erosion resistance
Hardness: 2200-2400 HV
Magnetic Properties: non-magnetic verified using magnetic permeability
Tester, results below 1.010 are acceptable however results below 1.005 are common
Density: 0.400 lbs/in3 (11.1 g/cm3)
Depending on application, material composition is tailored for the desired outcome. Where higher wear and less impact is present, a higher percentage of tungsten carbide particles to matrix alloy can be employed.
On certain applications, like hard banding on non-mag tools such as drill collars, specific ratios have been developed in design to wear at a planned rate and not induce wear into the base material. When the incorrect ratio is employed, the hard band can actually be too hard and resist wearing where the base material will wash away adjacent to the band creating what is known in the industry as ‘mud rings.’ While we have the ability to repair these mud rings, it is known that the repair is never as strong as the original material, so all attempts to protect that original material qualities are paramount.
Premium NON-Mag PTA COATINGS
In addition to the Standard, economical option for NON-Mag applications like hardbanding, etc. We offer 2 other premium selections. These are desirable in extreme wear conditions or when the design is not for a controlled wear band environment.
TM-NMS – Non-mag PTA coating using much harder, and larger percentage of SPHERICAL carbide particles. In addition to that, a harder metal matrix alloy is employed giving a much higher wear coefficient. Ask us for more info!
TM-NMT – Non-Mag PTA coating where Tungsten carbide Tiles are bound using proprietary techniques and our PTA process. The is for the most extreme wear applications on non mag tools like Stabilizers, etc.
Cracking of Hardfacing on Stabilizers and collars
Hardfacing is not designed for joining steels together, but rather to resist impact and/or abrasion. Hardfacing deposits can be so hard that they surrender any, or all, ductility.
Immediately after welding the deposited hardfacing material begins to contract, or change shape, as the heat dissipates. Since most hardfacing deposits have nearly no ductility, the welds will crack. This alarms many welders and end users but is not a need for concern. Most often, these cracks are transverse (cross) cracks, which are very beneficial to relieve the residual stress in the weld bead.
Cracking is a common during the hardsurfacing process, and is considered acceptable as long as it does not extend into the base material or exceed a specific length. According to the TH Hill DS-1 Spec Section 22.214.171.124, a widely used specification for hardsurfacing, “Crack indications are acceptable in hardsurface metal provided that crack width is no greater than 3/32 inch, and crack depth does not exceed 0.25 inches.”
The more wear resistant deposits, with higher alloy contents, have a tendency to form hairline cracks across the weld beads. This is desirable as it will reduce and possibly eliminate the tendency for distortion.
To summarize, the tensile ductility of the hardfacing is reduced and cracks occur as a result of welding contraction strain. This type of cracking will not affect the wear resistance and is acceptable.
Maunfacturing – Fabrication
We have the ability to provide turnkey fabrication on components requiring hard surfacing in house.