449 thermal analyzer

Example 13

A cylindrical (Ø10 mm) grade 2 titanium sample was treated in a Netzsch 449 Thermal analyzer (furnace). The furnace was evacuated and backfilled with argon gas twice and a continuous gas flow consisting of 10 ml/min Ar, 10 ml/min CO₂ and 40 ml/min CO was applied. The sample was heated to 1000° C. at a rate of 20° C./min in the same gas mixture and upon reaching the temperature held there for 20 hours. Cooling was carried out at 50° C./min in the flowing process gas. The applied gas resulted in oxidation of the titanium represented as a zone of oxygen in solid solution (‘diffusion zone’) as shown in FIG. 21.

Example 12

A cylindrical (Ø10 mm) grade 2 titanium sample was treated in a Netzsch 449 Thermal analyzer (furnace). The furnace was evacuated and backfilled with argon gas twice and a continuous gas flow consisting of 10 ml/min Ar, 30 ml/min CO₂ and 20 ml/min CO was applied (pCO=0.33 atm and pCO₂=0.50 atm). The sample was heated to 1000° C. at a rate of 20° C./min in the same gas mixture and upon reaching the temperature held there for 20 hours. Cooling was carried out at 50° C./min in the flowing process gas. The applied gas resulted in oxidation of the titanium, as shown in FIG. 19, which shows a layer of titanium oxide of a thickness of about 25 μm and a diffusion layer of oxygen in solid solution in titanium (below the oxide layer)—the diffusion layer had a thickness of about 100 μm thickness.

The hardness profiles of the treated samples were recorded and these are illustrated in FIG. 20. The dotted horizontal lines illustrate the core hardness of the titanium metal.

Example 16

A cylindrical (Ø10 mm) grade 2 titanium sample was treated in a Netzsch 449 Thermal analyzer (furnace). The furnace was evacuated and backfilled with argon gas twice and a continuous gas flow consisting of 10 ml/min Ar and 40 ml/min CO was applied. The sample was heated to 1000° C. at a rate of 20° C./min in the same gas mixture and upon reaching the temperature held there for 4 hours. Cooling was carried out at 50° C./min in the flowing process gas. This resulted in carbo-oxidation of the titanium. The carbo-oxidized component was subsequently treated in a tube-furnace equipped with pure N₂ gas. Nitriding was carried out at 1000° C. for 1 hour in flowing N₂ gas (1 l/min). This resulted in partial conversion the C—O-rich surface case into a C—O—N containing surface. The diffusion zone is now significantly harder as illustrated in the hardness profile presented in FIG. 24.

Example 10

A cylindrical (Ø10 mm) grade 2 titanium sample was treated in a Netzsch 449 Thermal analyzer (furnace). The furnace was evacuated and backfilled with argon gas twice and a continuous gas flow consisting of 10 ml/min Ar and 40 ml/min CO was applied. The sample was heated to 1000° C. at a rate of 20° C./min in the same gas mixture and upon reaching the temperature held there for 4 hours. Cooling was carried out at 50° C./min in the flowing process gas. A mixed interstitial compound TiO_xC_1-x and a mixed interstitial solid solution based on carbon and oxygen (‘diffusion zone’) have formed. The sample was immersed in 0.25 wt % HF with pH adjusted to 1 with HCl; the results after 16 days of treatment are shown in FIG. 17, where FIG. 17a shows that the untreated reference suffered from corrosion upon exposure to the solution, whereas no signs of corrosion for the sample hardened according to the invention were observed after 16 days (FIG. 17b). The sample not hardened according to the invention showed signs of corrosion immediately upon exposure to HF as evidenced by discoloration of the solution in which the sample was placed.

Example 9

A cylindrical (Ø10 mm) grade 2 titanium sample was treated in a Netzsch 449 Thermal analyzer (furnace). The furnace was evacuated and backfilled with argon gas twice and a continuous gas flow consisting of 30 ml/min Ar and 20 ml/min CO was applied. The sample was heated to 1000° C. at a rate of 20° C./min in the same gas mixture and upon reaching the temperature held there for 4 hours. Cooling was carried out at 50° C./min in the flowing process gas. A mixed interstitial compound TiO_xC_1-x and a mixed interstitial solid solution based on carbon and oxygen (‘diffusion zone’) have formed. The case depth is approximately 200 μm. The hardness profiles of the TiO_xC_1-x and the C+O rich diffusion zone are illustrated in FIG. 16, which also shows (as a dotted line) the hardness of the untreated material, which corresponds to the core hardness of the treated material.

Example 4

A cylindrical (Ø10 mm) grade 5 titanium sample was treated in a Netzsch 449 Thermal analyzer (furnace). The furnace was evacuated and backfilled with argon gas twice and a continuous gas flow consisting of 20 ml/min Ar and 30 ml/min CO (60% CO) was applied. The sample was heated to 1000° C. at a rate of 20° C./min in the same gas mixture and upon reaching the temperature held there for 20 hours. Cooling was carried out at 50° C./min in the flowing process gas. This resulted in carbo-oxidation of the titanium as seen in FIG. 9, which shows reflected light optical microscopy of cross-sections. A mixed interstitial compound TiO_xC_1-x and a mixed interstitial solid solution based on carbon and oxygen (‘diffusion zone’) have formed. The hardness of the TiO_xC_1-x is 1416 HV0.025. The case depth is approximately 80 μm. The core has transformed into an α/β structure, i.e. simultaneous core and surface hardening took place.

Example 18

A zirconium sample was treated in a Netzsch 449 Thermal analyzer (furnace). The furnace was evacuated and backfilled with argon gas twice and a continuous gas flow consisting of 10 ml/min Ar and 40 ml/min CO was applied. The sample was heated to 1000° C. at a rate of 20° C./min in the same gas mixture and upon reaching the temperature held there for 1 hour. Cooling was carried out at 50° C./min in the flowing process gas. This resulted in carbo-oxidation of the zirconium. The surface hardness was 800 HV.