Search results

A number of corrosion studies involving stainless steel material have been carried out.
The corrosion progression rate is affected by the high stress because the high stress concentrations at the initial austenitic grain boundaries induced more pit nucleation [9], hence we examined the strain distribution in tensile test on finite element analysis (FEA).

The most common cracks encountered in CSEF materials are [5]: - Hydrogen cracking - Stress corrosion cracking (especially if the welds are subjected to moisture after welding) - Cracking (due to poor ductility) during transportation of field erection (this has occurred on many occasions in T91 to P91 tube to header connections in HRSGs) - Accelerated "Type IV" cracking caused by elevated magnitude transverse weld residual stress (Type IV-cracking nucleates and propagates in the intercritical, fine grain region of HAZ) For the case of P91 and P22 weld joint that is not subjected to PWHT, it will have un-tempered hard martensite (with Hardness >400 HV), high residual stress and may have elevated levels of hydrogen.
Fig. 2 Post Weld Heat Treatment carried out on weld between A335 P91 and A335 P22 Pipes During PWHT of a dissimilar metal weld between materials of two different P Numbers which require PWHT at different temperatures, the PWHT temperature specified was for the material requiring higher PWHT temperature.

Treatment at high temperature, respectively 1050°C/1h (fig.2c), makes the structure with very big grains, each of them having inside many lamellar distribution of a and b solid solution.
ACKNOWLEDGMENTS This work was supported by Romanian POSDRU project number 60203.

The corrosion rate was calculated using the following equation [6-7]: (1) where: jcorr is the corrosion current density , M – molecular weight of iron, n – number of electrons exchanged, r - iron density.
In result of laser treatment different oxides and fine grains form on the surface of coating, which leads to different corrosion characteristics.

The diffusion of gaseous molecules through the grain boundaries of the organic active layer into the channel region is critical.
A number of methods has been developed to improve electrical conductivity and sensitivity of OTFTs, such as doping carbon nanotubes (CNTs) or using metal oxide materials, etc[6,7].

M— Nickel ions or Manganese ions; L—chelating molecules; n—chelating number; β1，β2，βn—chelating equilibrium constant; Table 1, The reaction equation and equilibrium constant in the solution No Equation lgKβ 1 NH3+H+=NH4+ lgKah=9.27 2 H2O=H++OH- lgKw=-14.0 3 Ni(OH)2(s)=Ni2++2OH- lgKspnh=-13.7 4 Ni2++OH-=Ni(OH)+ lgKnh1=3.97 5 Ni2++2OH-=Ni(OH)20 lgKnh6=7.55 6 Ni2++3OH-=Ni(OH)3- lgKnh3=11.33 7 2Ni2++OH-=Ni2(OH)3+ lgKnh5=3.3 8 Ni2++NH3=Ni(NH3)2+ lgKnn1=2.8 9 Ni2++2NH3=Ni(NH3)22+ lgKnn2=4.04 10 Ni2++3NH3=Ni(NH3)32+ lgKnn3=5.77 11 Ni2++4NH3=Ni(NH3)42+ lgKnn4=6.96 12 Ni2++5NH3=Ni(NH3)52+ lgKnn5=2.71 13 Ni2++6NH3=Ni(NH3)62+ lgKnn6=2.74 14 Mn(OH)2(s)=Mn2++2OH- lgKspmh=-12.8 15 Mn2++OH-=Mn(OH)+ lgKnh1=3.4 16 Mn2++3OH-=Mn(OH)3- lgKnh2=7.3 17 2Mn2++OH-=Mn2(OH)3+ lgKnh4=3.4 18 2Mn2++3OH-=Mn(OH)3+ lgKnh5=17.1 19 Mn2++NH3=Mn(NH3)2+ lgKmn1=1.0 20 Mn2++2NH3=Mn(NH3)22+ lgKmn2=1.54 21 Mn2++3NH3=Mn(NH3)32+ lgKmn3=1.70 22 Mn2++4NH3=Mn(NH3)42+ lgKmn4=1.30 The relations in co-precipitation system are as follows
So, when pH=11 and [NH3]=0.8-1mol/L, the morphology of Ni1/2Mn1/2(OH)2 is the best, and the total ammonia concentration in the reactor close to 0.4mol/L at this moment; when the ammonia concentration is lower, the particle size of formed Ni1/2Mn1/2(OH)2 is smaller and prone to agglomeration, the particles are large; while the ammonia concentration is higher, nickel ion and ammonia is easily formed complex and the precipitation is incomplete and the speed of grain growth is slow.

Introduction Powder metallurgy includes a number of steps, to produce parts with varied characteristics.
For high-pressure values, the contact surfaces expand, the grains deform plastically and the porosity rate in the final compact is insignificant.

Owing to the high cooling rate, these components have extremely fine cellular dendrites with Laves phase precipitating in the sub-grain boundaries according to the nature of SLM process [[] M.
Tensile samples show a greater number of fine needle-like γ′′ phases (Fig.8a), while compression samples show some larger size δ precipitates (Fig.8b).

The maximum of the distribution corresponds to the most probable domain configuration and its width reflects the number of available domain states.
The fast relaxation with time constants in the order of a few seconds is attributed to the presence of a conductive grain boundary phase which should be avoided by optimizing film deposition.

Niobium acts as an inhibitor of crystal growth, increasing the crystallization temperature and ensuring the growth of crystals from a large number of centers [3].
Shvindlerman, Grain boundary migration in metals: thermodynamics, kinetics, applications (CRC Press 2010)