Introduction to Trimay Overlays
Five different types of overlays are available from Trimay. They include:
- Nano and
- Two types of Tungsten overlays
Each of these will be described in more detail in the following sections.
The wear characteristics of these overlays are different from each other’s but are better than the regular austenitic, hardened or any other type of steel.
Selection of Overlays
Several variables determine the length of wear of an overlay in each application. Therefore, customers opting for Trimay overlays are advised to do so after considering the following parameters:
- The service life expected from a protective overlay
- The level of abrasiveness of the material that will flow through the pipe to be overlaid
- The extent of impact that the overlay will be exposed to
Types of Trimay Overlays
Complex overlays are suitable for corrosive, high-temperature environments and are made using a unique blend of carbides bonded in the form of a tight crystalline matrix. The T161 complex overlay can operate in temperatures up to 650°C or 1202°F and possesses better wear characteristics than the chrome overlays from Trimay. The T161 complex overlay is best suited for heavy wear applications with the direct impact probability ranging from mild to moderate.
Due to their strong wear deterrent and impact absorbing nature, chrome overlays find the widest use in industrial applications. Three types of chrome overlays are available from Trimay, namely, T138, T156 and T157. They are well suited for operations in moderate-to-heavy wear environments and can absorb mild to moderate impact.
Tungsten overlays from Trimay have the toughest wear characteristics among all overlays. They are available in matrix content above and below 50%. The major distinguishing factor for the two types is that the above 50% Tungsten overlay is available as a single layer overlay only whereas the below 50% type can be offered up to three layers. Tungsten overlays from Trimay also absorb impact better than the other two types of overlays.
Nano - Borocarbide Overlays
T171* borocarbide overlays are the latest class of overlays from Trimay. This class of products was co-developed by Trimay with an advanced materials company, NanoSteel Company. Nano is a sub-micron borocarbide alloy that displays far superior wear characteristics than tungsten overlays at much less cost. The T171* overlay from Trimay is best suited for heavy-to-extreme wear applications with moderate direct impact.
Trimay’s T171 Overlay
Description of the T171 Overlay
The T171* overlay is made of iron-based steel comprising Trimay’s unique proprietary chemical composition having submicron microstructure. This overlay is suitable for extreme environments. Trimay has partnered with The NanoSteel Company, Inc., a global leader in nanomaterials production and R&D, to develop the T171* overlay. It has excellent glass forming chemistry that permits high levels of undercooling during welding. This helps in extremely refined nanosize- range crystalline microstructure, which gives the T171* much better hardness compared to conventional carbide solutions.
Major Performance Characteristics of the T171 Overlay
The T171* overlay has a hardness test rating of 68 - 71 HRc. It has excellent hardness from the weld interface along the entire overlay in single pass applications, giving the overlay full protection throughout. It can maintain this hardness even during exposure to high temperatures. The micrograph below shows how maximum hardness is achieved within the weld overlay interface. In the micrograph, Hardness values were measured from a single pass T171* overlay applied to a substrate of 44W/300W mild steel plate.
HRc hardness properties are consistent throughout the entire layer
Unique Wear Resistance
T171* overlay has excellent resistance to severe sliding abrasion in harsh service environments. It can be built up to overlay thickness of 1/2” in two passes as needed with all layers. This provides wear resistance up to 0.08 - 0.10 g (±0.03) mass loss in ASTM G65-04 abrasion tests.
High Impact Resistance
T171* overlay has excellent toughness equivalent to 400 Brinell Q&T plate and this is due to in-weld formation of high quantities of refined complex borocarbide phases, surrounded by ductile ferrite phases. The borocarbide phases are fully wetted by the matrix and avoid delamination, premature pull-out, and crack nucleation. The refined nature of the borocarbide phase reduces stress concentration sites and the ductile matrix provides good crack blunting and bridging, thus resulting in better impact resistance.
T171 microstructure showing uniform distribution of borocarbide phases
Production and Installation of the T171 Overlay
T171* overlay can be used as a wear plate solution for low alloy and carbon steel substrates and . Trimay’s proprietary Submerged Arc Bulk Overlay Welding Process is used for overlaying a T171* wear plate. The overlay can be cut and fabricated to different specifications just like chrome carbide overlays. Forming or rolling is achieved using press brakes while cutting is accomplished through plasma arc or water jet methods, but it cannot be flame cut. Thickness and the position of the weld (on the inner or outer diameter) determine the formability of the overlay. For low-precision applications, it is possible to remove the T171* overlay material using carbon arc gouging. T171* overlays are non-machinable, and based on requirement, can be surface-finished by EDM or grinding. Fillet or plug welding are the common methods for installing a T171* wear plate and it can be fabricated or bolted with inserts for installation. The weld seams in the wear plate should be overlaid with the T171* weld wires, exclusively available for customers of Trimay, to ensure uniform wear.
Trimay develops and manufactures the highest quality wear overlays for customers seeking to maximize efficiency by extending the life of equipment, parts and pipelines exposed to severe wear conditions. Trimay achieves its high-quality standard through research and development, partner companies and exclusive suppliers, as well as through in- house experimentation and process optimization.
This information has been sourced, reviewed and adapted from materials provided by Trimay Wear Plate Ltd
For more information on this source please visit Trimay Wear Plate.