Studija korozivnih svojstava zaštitnih TiN-prevlaka u sulfatnoj sredini

The paper deals with the corrosion properties of TiN coatings in a 1 % Na2SO4 environment, which were determined by gravimetric analysis and corrosion potential measurement. The evaluation of the corrosion effect of the test electrolyte was completed by the samples surface observation by the LEICA macroscope before and after their exposure in a sulphate environment.Rad se bavi korozivnim svojstvima prevlaka TiN uronjenih u 1 % Na2SO4 sredinu. Svojstva su utvrđena gravimetrijskom analizom i mjerenjem potencijalne korozije. Procjena korozivnog efekta na elektrolit testa upotpunjena je pregledom povšine uzoraka makroskopskom LEICA prije i nakon izlaganja u sulfatnoj sredini

Fatigue Characteristics of Laser Welded DC06EK and DP600MC Steel Sheets

Welding of different types of steel is fundamental proces for the production of car bodies. Fatigue degradation is still a significant factor in long-term use. Current trends welding and combinations of different types of steel are used. The specific form of the course of fatigue in the welded joints is followed. Test samples loaded fatigue tests, microscopic and scanning electron microscopy analysis of welded joints of steel type IF (DC06EK) and DP (DP600MC) are done. The resulting values of endurance tests are graphically processed by the Wöhler curve

The Mechanical and Brittle Properties of Gas Pipeline in Service

The paper deals with the determination of mechanical and brittle properties of gas pipeline after more than 40 years in operation. The heat affected zone in weld of pipeline is the risk area in terms of embrittlement structure, which resulted in an increase of yield strength and shift of transit temperature to more positive values. The specimens were cut from heat affected zone for this reason. The tensile test according to ISO 6892-1 showed the increase in yield strength: it had a value of 295 MPa at the beginning operation and 400 MPa after more than 40 years in pipeline operation was recorded. The transition temperature at the value of 20°C was determined by using the Charpy impact test according to EN 10045-1. The operators of gas pipelines report that the mean temperature on the outer surface of pipe is about 4°C during the winter. The risk of brittle fragile is very likely if the transition temperature is higher than operating temperature