Influence of thermal effects on the micromechanical properties of the nickel-chromium coating obtained by gas powder laser cladding
<b>Introduction</b>. Nickel-chromium coatings can be used in parts that are operated at high temperatures (hot deformation dies, rolls of rolling mills, live rolls, parts of turbines, heat exchangers, etc.). A promising method of coating deposition is gas powder laser cladding, which forms coatings with increased hardness and uniformity. A modern method for evaluating the mechanical properties of nickel-chromium coatings is instrumental microindentation, which records diagrams during loading and unloading of the indenter. <b>The aim</b> of the work is to study the effect of thermal action in the temperature range of 800…1050 °C on the micromechanical properties of the NiCrBSi coating PG-10N-01 obtained by gas powder laser cladding. <b>Methods of research</b> are instrumental microindentation and scanning electron microscopy using energy-dispersive microanalysis. <b>Results and discussion</b>. Thermal action at a temperature of 800 °C only slightly reduces the strength characteristics of the coating, while the dissolution of the strengthening phases in the structure of the coating when heated to 900 °C leads to a significant decrease in the hardness characteristics and parameters that characterize the resistance to elastic-plastic deformation. The formation of a “frame-like” structure with a base of large carboborides Cr<sub>2</sub>(B,C) and borides Cr<sub>2</sub>B with increased elastic moduli upon heating to 1050 °C (holding for 1 h, cooling in air) leads to a strong increase in the average contact elastic modulus to ~ 280 GPa (with an average level of elastic modulus of ~ 200 GPa in the coating after cladding and after additional heating to 800 and 900 °C). Also, the strength characteristics of microindentation (Martens hardness and indentation hardness at maximum load) and calculated parameters that indicate the improved ability of the coating with a “frame-like” structure to deform in a “favorable” elastic region, as well as to resist mechanical contact loads even after the beginning of the plastic flow, grow to maximum values.