Hardness of matrix HO, MPa

1. 3000 (initial state)

Hardness of surface HS, MPa

DOI: http://dx.doi.org/10.5772/intechopen.82545

Relative gain of surface hardness К, %

Surface Treatment of Titanium Alloys in Oxygen-Containing Gaseous Medium

R1 3050 3630 19.0 45–50 ≤505 20.0 R2 4030 32.0 30–35 ≤495 18.0 R3 4080 34.0 60–65 ≤465 11.0 R4 4860 60.0 60–65 ≤445 6.0 R5 5550 82.0 30–35 ≤500 19.0

Fatigue strength of titanium alloy VТ5, under rotating bending conditions, depending on the level of surface

Average relative gain of surface hardness К, %

Average relative gain of surface hardness К, %

2. 2650 3095 12.5 25–30 ≤430 28.5 3. 3575 30.0 30–35 ≤420 25.5

Fatigue strength of titanium alloy OТ4-1, under rotating bending conditions, depending on level of surface

Depth of hardened zone l, μm

Depth of hardened zone l, μm

Depth of hardened zone l, μm

3020 ≤1 5–10 ≤525 0

2850 4.0 5–10 ≤335 0

3200 5.0 5–10 ≤420 0

Fatigue strength σ�1, MPa

Fatigue strength σ�1, MPa

Fatigue strength σ�1, MPa Relative gain of fatigue strength Δσ�1, %

Relative gain of fatigue strength Δσ�1, %

Relative gain of fatigue strength Δσ�1, %

1. The kinetic parameters of interaction and regularities of solid solution

2. 3000 3145 5.0 100–120 ≤580 10

Fatigue strength of titanium alloy VT16, under rotating bending conditions, depending on level of surface

hardening of titanium alloys VT1-0, VT5, OT4-1, and VT16 under conditions of thermodiffusion saturation in rarefied gas medium are determined.

2. It is shown that under the same conditions of saturation (T, τ, P), the hardened layers of various parameters (H, l) are formed on the titanium alloys. The monophase α-titanium alloys VT1-0 and VT5 and near-α-alloy ОТ4-1 are the most sensitive to the conditions of gas saturation: the gain of surface hardness and its gradient in the hardened layer increase sufficiently. With the increasing

of β-phase (OT4 ! VT16), changing of the parameters of CTT has less

#### Figure 23.

Fatigue strength of titanium alloy VT5, under rotating bending conditions, as a function of depth of hardened zone, when level of surface hardening is constant K = 30%.

characteristics. In addition, vice versa for each depth of hardened zone, the optimal level of surface hardening exists. Furthermore, it can be forecasted that for each alloy the optimal relation between parameters K and l exists that provides absolutely maximal gain of fatigue strength. Such parameters of gas-saturated layers can be determined as optimal parameters of alloy hardening. The aim of the next step lies in the search of the optimal level of K and l parameters of the hardened zone.

Surface Treatment of Titanium Alloys in Oxygen-Containing Gaseous Medium DOI: http://dx.doi.org/10.5772/intechopen.82545


Table 25.

Fatigue strength of titanium alloy VТ5, under rotating bending conditions, depending on the level of surface hardening K and depth of hardened zone l.


#### Table 26.

Fatigue strength of titanium alloy OТ4-1, under rotating bending conditions, depending on level of surface hardening K and depth of hardened zone l.


Table 27.

Fatigue strength of titanium alloy VT16, under rotating bending conditions, depending on level of surface hardening K and depth of hardened zone l.
