Graphite hearth plates and work trays are the load-bearing floor of your vacuum furnace hot zone. They must withstand repeated thermal cycling, the weight of the work load, and quench-gas pressure pulses — all while resisting oxidation at temperatures above 1,000 °C. Expo Advanced Materials manufactures precision graphite hearth plates and trays in India, customised to your furnace dimensions and load requirements.
Types of Hearth Plates and Trays We Manufacture
- Flat hearth plates — Plain flat slabs machined to ±0.5 mm flatness tolerance. Used as furnace floor plates or inter-layer separators in multi-tier loading.
- Ribbed hearth plates — Integral machined ribs on the underside provide structural stiffness and reduce dead weight. Ribs also allow gas flow underneath for uniform heating.
- Work trays with raised edges — Tray form with 10–30 mm raised perimeter walls to retain small parts during processing and gas quenching.
- Grid / open-structure trays — Lattice-pattern trays for maximum gas circulation around parts during quenching cycles. Essential for AMS 2750 temperature uniformity compliance.
- Stacking posts and pillars — Machined graphite pillars for multi-tier batch loading. Customised height, diameter, and top/bottom socket geometry.
Materials and Grades
We machine hearth plates from high-density isostatic graphite (1.80–1.88 g/cm³) for maximum load-bearing capacity, or from fine-grain extruded graphite for cost-sensitive applications. For aerospace-certified furnaces requiring AMS 2750 compliance, we recommend high-density isostatic grades with documented material properties.
Standard Sizes We Stock
| Form | Max Size | Standard Thickness |
|---|---|---|
| Flat plate | 1,200 × 600 mm | 20–80 mm |
| Ribbed plate | 1,000 × 600 mm | Overall 50–100 mm |
| Work tray | 800 × 500 mm | 25–60 mm |
| Circular plate | Dia 1,200 mm | 20–80 mm |
Applications
- Vacuum hardening and case-hardening furnaces
- Vacuum brazing furnaces (aluminium and stainless steel)
- Low-pressure vacuum carburising (LPC) systems
- Vacuum sintering of cemented carbide and PM parts
- Atmosphere annealing furnaces
How to Order
Share your furnace internal dimensions, load weight per tray, and any special features (holes, notches, stacking sockets). We design and quote within 24 hours. OEM replacement orders: provide furnace model or part number.