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Tungsten Carbide Tiles for Radial Bearings in Drilling Motors: An Engineering Guide

  • J.T. Thomas
  • Apr 21
  • 9 min read

J. T. Thomas | Southern Carbide Company | Veteran-Owned | www.southcarb.com


Introduction

The global directional drilling market is projected to grow from $7.7 billion in 2025 to $14.4 billion by 2032, reflecting a compound annual growth rate of 9.34%, according to Coherent Market Insights.[1] Behind every foot of directional hole lies a mud motor, and inside every mud motor, radial bearings quietly determine whether a run ends on schedule or with an expensive trip out of hole.

Radial bearing failure is one of the leading causes of downhole motor downtime. As horizontal and directional drilling programs push motors harder, longer, and at sharper build angles, the materials that protect radial bearing surfaces become a decisive factor in overall motor reliability. Tungsten carbide (TC) tiles have emerged as the preferred solution for mud-lubricated radial bearings, delivering 300-400 hour run life and superior resistance to the abrasion, erosion, and thermal stress inherent in downhole environments.


This guide covers how mud motor radial bearing's function, why TC tiles outperform competing surface technologies, how to select the right tile configuration and grade, and how pre-mounted tile sheets from Southern Carbide Company (SCC) can streamline your bearing manufacturing process. WC for Radial Bearings


Radial bearing sleeve with tungsten carbide tile lining  


How Mud Motor Radial Bearings Work

Positive displacement motors (PDMs) convert hydraulic energy from circulating drilling fluid into mechanical rotation at the bit. The power section, a helical rotor spinning inside an elastomeric stator, generates torque that is transmitted through a connecting rod and drive shaft to the drill bit. The bearing assembly sits at the bottom of the motor, between the power section and the bit, and it serves two critical functions: supporting axial loads (weight on bit) and absorbing the radial side loads imposed on the rotating drive shaft.


Radial bearings within this assembly provide centralization and lateral support for the drive shaft. As noted by Drilling Manual, we use metallic or nonmetallic radial bearings above and below the thrust bearings to protect and absorb lateral side loading of the drive shaft.[2] In a mud-lubricated (non-sealed) configuration, which is the most common design in directional drilling, a controlled portion of the drilling fluid, typically 4-10%, is diverted through the bearing pack. This diverted fluid serves a dual purpose: it cools the bearing surfaces and provides lubrication across the radial and thrust bearing interfaces, as described by Drilling Formulas.[3]


The radial bearing also acts as a flow restrictor. By regulating the volume of fluid passing through the bearing assembly, it maintains a controlled pressure differential that sustains fluid film lubrication under varying downhole conditions. This means the bearing surface material must withstand not only mechanical contact loads but also the erosive effects of drilling fluid carrying abrasive solids at high velocity.

Standard bearing body materials include 4140, 4145, 4330V, and 4340 alloy steel. The surface treatment applied to these steel substrates determines bearing longevity, and this is where tungsten carbide tiles have proven their value.


Why Tungsten Carbide Tiles Outperform Alternatives

Not all TC bearing surfaces are created equal. There are several competing approaches to protecting radial bearing wear surfaces, and each has distinct performance characteristics.


Tungsten Carbide Tiles vs. Grain Matrices

TC grain bearings embed small tungsten carbide balls (typically 0.7-1.2 mm diameter) in a matrix material on the bearing surface. While this approach works for small or complex-geometry applications, grain matrices have a lower hard-alloy coverage percentage, meaning more of the bearing surface is exposed matrix material vulnerable to washout and erosion. Under magnification, grain bearings show pockets where the matrix erodes between the embedded balls, which, while sometimes beneficial for trapping lubricating fluid, ultimately compromises bearing life in high-flow environments.


Tungsten Carbide Tiles vs. Cladding and Welded Overlays

Proprietary cladding processes, such as Kennametal’s Conformal Clad technology, apply a tungsten carbide layer through brazing or diffusion bonding. While Kennametal has supplied over 300,000 Conformal Clad radial bearings since 1985, cladding and welded overlay processes have inherent limitations. The bonded layer is susceptible to chipping, cracking, and flaking, particularly under the thermal cycling and mechanical shock conditions found downhole. These failure modes can release debris into the mud stream, potentially damaging other BHA components.


The Tungsten Carbide Tile Advantage

Individual tungsten carbide tiles, brazed directly to the bearing substrate, offer several distinct advantages:

•        Resistance to chipping, cracking, and flaking. Because each tile is an independent, fully sintered tungsten carbide piece, localized damage does not propagate across the bearing surface the way it does in a continuous cladding layer.

•        High thermal conductivity. TC tiles conduct heat efficiently away from the bearing contact zone, effectively eliminating thermal cracking, which is a common failure mode in cladding and overlay systems subjected to high downhole temperatures.

•        Hard alloy coverage exceeding 55%. Tile-based designs achieve superior hard-phase surface coverage compared to grain matrices, meaning more of the bearing surface is protected by tungsten carbide rather than vulnerable binder or matrix material.

•        Proven 300–400-hour typical bearing life. In standard mud-lubricated applications, TC tile bearings consistently achieve run lives in this range, reducing trip frequency and associated non-productive time.


Round and rectangular tiles 

 

Round vs. Rectangular Tile Configurations

TC tiles for radial bearings are available in two primary geometries, each with different performance characteristics.


Rectangular Tiles

Rectangular tiles (common sizes include 6 mm x 5 mm x3 mm, and 13 mm x 5 mm x 3 mm) are the most widely used configuration in mud-lubricated radial bearings. They typically achieve approximately 55% hard-alloy surface coverage. The gaps between tiles create channels that allow drilling fluid to flow across the bearing surface, aiding in cooling and debris removal. This design is the industry standard for general-purpose directional drilling applications and offers a well-proven balance of performance, manufacturability, and cost.


Round Button Style

Round button-style tiles achieve greater than 70% surface area coverage, a significant improvement over rectangular configuration. The key differentiator is that round button arrangements eliminate direct pathways for fluid wash and erosion between tiles. In rectangular tile layouts, the linear channels between tiles can become high-velocity erosion paths that progressively widen, undermining the bearing surface. Round button geometry disrupts this flow pattern, reducing localized erosion.


When to Choose Each Configuration

Round button-style bearings are best suited for high-erosion environments where drilling fluid carries heavy solids loading or where extended run life beyond the standard 300–400-hour window is required. Rectangular tiles remain the practical choice for standard drilling conditions where the proven 55% coverage rate provides adequate protection, and the simpler manufacturing process keeps per-unit costs lower.


Grade Selection: YG11C vs. YG15C for Radial Bearings

Choosing the correct tungsten carbide grade is as important as choosing the right tile configuration. The two most relevant grades for radial bearing applications are YG11C and YG15C. The "YG" designation refers to the WC-Co (tungsten carbide-cobalt) composition system, and the number approximates the cobalt binder percentage.

Property

YG11C

YG15C

WC Content

89.5-90.5%

84.5-85.5%

Cobalt Content

10.5-11.5%

14.5-15.5%

Hardness (HRa)

89.5-90.5

87.0-88.0

Transverse Rupture Strength (TRS)

2,000 N/mm²

2,200+ N/mm²

WC Grain Size

1.2-4.0 µm

1.2-4.0 µm

Best Application

General directional drilling; balanced hardness and shock resistance

Extreme shock, vibration, and high-impact environments

 

How to Choose Between Them:

YG11C is the standard workhorse grade for radial bearing tiles. With approximately 11% cobalt binder, it offers an excellent balance of hardness (89.5-90.5 HRa) and toughness (TRS of 2,000 N/mm²). The higher WC content delivers strong wear resistance, making it ideal for standard directional drilling programs, curve and lateral sections, and general mud motor service where abrasion resistance is the primary concern.

YG15C increases cobalt content to approximately 15%, which shifts the balance toward maximum toughness and impact resistance at the cost of slightly lower hardness. The higher TRS value (2,200+ N/mm²) means the material can absorb greater shock loads without fracturing. Choose YG15C for extreme drilling conditions: high-vibration environments, severe doglegs, aggressive build rates, hard/interbedded formations that generate impact loading, or any application where the risk of tile cracking from mechanical shock outweighs the risk of abrasive wear.

In practice, many bearing manufacturers stock both grades and select based on the planned well profile and formation characteristics. Some operators specify YG15C as a default for high-cost wells where the insurance against impact-related tile failure justifies the marginal reduction in abrasion resistance.


 

SCC’s Pre-Mounted Tile Sheets: Fabricated In-House, Customized to Your Application

One of the most time-consuming steps in radial bearing manufacturing is the manual placement of hundreds of individual TC tiles onto the bearing substrate before brazing. Tile-by-tile placement, even with the aid of a template, is labor-intensive, prone to spacing inconsistencies, and creates a bottleneck in production throughput.

Southern Carbide Company addresses this challenge with pre-mounted tungsten carbide tile sheets. fabricated at our facility in Texas.


Fabricated Locally, Not Just Supplied


SCC is not a reseller of imported tile sheets. We fabricate pre-mounted tile sheets in-house at our local facility. This is a critical distinction. Because the fabrication happens under our roof, we have direct control over tile spacing, arrangement patterns, carrier material, and quality at every step. More importantly, it means we can customize.

Every radial bearing design is different. Bore diameters vary, tile coverage requirements change by application, and some OEMs need non-standard tile sizes or spacing optimized for specific mud weights or flow conditions. Off-the-shelf sheets from overseas suppliers are fixed configurations, what you see is what you get. SCC’s in-house fabrication capability means we can work with your engineering team to develop a tile sheet configuration matched to your specific bearing geometry and performance requirements.

This level of customization requires detailed consultation. Our team works directly with bearing manufacturers to understand the application, review drawings, and recommend tile size, grade, spacing, and sheet dimensions that optimize performance for the intended service conditions. That conversation is part of how we do business, not an upsell. WC for Radial Bearings


Our standard configuration sheets are available for immediate shipment. For custom configurations, different tile sizes, modified spacing, alternative sheet dimensions, or specific grade combinations, more time may be necessary to fabricate or design your sheet. Contact our team today to learn if our standard sheet configuration will meet your needs, or if a custom design is needed.


How It Works

SCC supplies TC tiles pre-mounted in precise, uniform spacing on a plastic carrier sheet. The manufacturer simply positions the sheet onto the bearing substrate, and the tiles are already arranged at the correct spacing for brazing. The plastic carrier material burns away cleanly during the brazing cycle, leaving only the properly positioned tiles bonded to the bearing body.


Pre-mounted sheets eliminate manual tile placement, reducing assembly time per bearing from hours to minutes. Consistent tile spacing across every sheet means consistent bearing quality, removing the operator-dependent variability that comes with hand placement. For bearing manufacturers running production volumes, the throughput improvement is substantial.


No 5-8 week overseas lead times. Standard sheets ship now from Conroe, Texas. Custom sheets are fabricated locally with timelines you can plan around, not container schedules you cannot.


Pre-arranged tungsten carbide tiles on sheet backing for efficient installation 

 

Market Context: Why Quality TC Bearings Matter Now

Despite the current softness in the U.S. rig count, the long-term trajectory for directional drilling is firmly upward, and with it, demand for reliable downhole motor components.


As of March 20, 2026, the Baker Hughes U.S. rig count stood at 552 total rigs, down 41 rigs (7%) year-over-year.[4] Oil rigs declined 72 units (14.8%) while gas rigs increased 29 units (28.4%), according to Seeking Alpha.[5] However, the shift toward natural gas and the growing proportion of horizontal and directional wells in the active rig fleet means each rig is consuming more motor hours, not fewer.

The global drilling mud motor market was valued at $1.3 billion in 2024 and is forecasted to reach $2.4 billion by 2033, according to Market Intelo.[6] Separately, Cognitive Market Research sizes the drilling mud motors market at $415.6 million in 2024, projected to reach $703.08 million by 2031 at a 7.80% CAGR, with North America representing the dominant share at $166.24 million.[7]

For bearing manufacturers and downhole tool OEMs, this growth translates directly into increased demand for TC tiles. Investing in a reliable, domestic supply chain for tungsten carbide bearing materials is not just a quality decision; it is a supply chain risk mitigation strategy.


Conclusion

Tungsten carbide tiles remain the proven, preferred solution for mud-lubricated radial bearings in directional drilling motors. They outperform grain matrices, cladding, and welded overlays in abrasion resistance, thermal management, and service life. Choosing between round and rectangular configurations, and between YG11C and YG15C grades, allows engineers to optimize bearing performance for specific well conditions.

Southern Carbide Company fabricates pre-mounted TC tile sheets in-house at our Texas facility, we are the manufacturer, not a reseller. Standard sheets in both YG11C and YG15C are in stock for immediate shipment. For non-standard bearing designs, our team works directly with your engineers to develop custom tile configurations matched to your specific geometry and service conditions. As a veteran-owned, US-based fabricator, SCC eliminates the long overseas lead times, fixed-configuration constraints, and supply chain uncertainty that come with sourcing from international suppliers.


Request a quote or start a custom consultation at www.southcarb.com.


Southern Carbide Company | Conroe, TX

Veteran-Owned | US-Based | In-Stock for Immediate Shipment


 


 

 

 

 

 

 

 

 

 
 
 

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