The performance effects by surface treating for worn parts in the glass forming machines

Yüzey işlemleriyle malzemenin sertlik, süneklik ve yorulma gibi mekanik özellikleri yanında sürtünme ve aşınma, oksidasyon ve korozyona karşı dayanıklılık özellikleri geliştirilmektedir. Sürtünerek çalışan makina elemanlarında belirli bir süre sonra ortaya çıkan aşınma problemlerini azaltmak için birçok yüzey iyileştirme teknikleri uygulanmaktadır. Yaşanan malzeme ve ürün kayıplarını, cam şekillendirme makinalarında minimuma indirmek ve söz konusu bu nedenlerden kaynaklanan duruş ve üretim kayıplarını azaltmak amacı ile gerçekleştirilen bu çalışmada; cam üretim makinalarında kullanılan kalıp kollarının malzemelerine alternatif malzeme ve kaplama türleri denenmiştir. Cam şekillendirme makinalarında mevcut kalıp kolu malzemesi olan AISI 420 kalite çeliğe alternatif olarak seçilen yüzeyi kaplanmış (nitrokarbürleme, sert krom kaplama, akımsız nikel kaplama ve borlama) üç farklı kalitede çelik (AISI 1040, AISI 4140 ve AISI 5140 kalite çelikler) malzeme, kalıp kollarındaki gerçek aşınma şartlarını simule edebilecek şekilde tasarlanan laboratuvar deneyleri için standart numuneler olarak hazırlanmıştır. Hazırlanan numunelere, metal-metal deneyleri yapılarak aşınma davranışları incelenmiştir. Oda sıcaklığında yapılan deneylerde nem ve sıcaklık sabit tutulmuştur.  Metal-metal aşınma deneylerinde, pimlere M2 kalite takım çeliği üzerinde aşınma testi uygulanmıştır. Farklı kalitede çelikten imal edilmiş olan kaplanmış taban malzemelerine uygulanan disk üstünde pim deneyi sonucunda kullanılmakta olan sert krom kaplı ve kaplamasız AISI 420 kalite çeliğin bor kaplı AISI 4140 kalite çelik malzemeye göre aşınma oranının sırasıyla yaklaşık 18.67 ve 184 kat daha çok olduğu tespit edilmiştir. Laboratuvar deneylerinin sonucunda AISI 4140 kalite çelik malzeme üzerine borlama ön plana çıkmış ve kalıp kollarının çalışma koşullarında aşınmaya en dayanıklı kaplama ve taban malzemesi olarak borlanmış AISI 4140 kalite çelik kabul edilmiştir.  Anahtar Kelimeler: Borlama, cam şekillendirme makineleri, kalıp kolu.The materials science in our country has provided significant developments in recent years. Glass industry has also needed to develop its glass forming machines and their parts for manufacturing the high quality with low price in this competitive environment for being in line with the demands of customers. As a result of this change in the business environment, the selection of materials being used in glass forming machines and the surface treatments applied on these materials have developed in accordance with the technology. Friction, wear, oxidation and corrosion properties of materials can be improved in addition to an increase of the ductility, hardness and fatigue properties of materials by using surface treatement. At glass forming machines, the mechanism which provides the mould to adapt into the glass machine, is called as the arm mould. Although mould and arm mould materials show similar properties, the responsibilities they undertake are totally different from each other. If the expectation from mould material can be described as resistivity to heat and surface roughness at metal glass interface, then the expectation from arm mould can be limited as resistivity to wearing and general suitability to the machine's material. The aim of this study to find an alternative material to the arm mould material as coated or uncoated conditions which are used at the glass forming machines in order to decrease the loss of discarded materials and product at glass machines. As alternatives to the existing arm mould material AISI 420, various kinds of steels (AISI 1040, AISI 4140, AISI 5140) were coated with different kinds of coatings as nitrocarburizing, hard chrome coating, boronizing and electroless nickel coating. To simulate the real working condition of arm moulds at the laboratory conditions, standard specimens are prepared for pin on disc tests. Specimens were at standard of ASTM G99 with a diameter of 4 mm. Specimens and disc are always cleaned at each test and dry friction conditions are provided. During laboratory tests, humidity and room temperature is controlled at %50±5 and 20±2oC respectively. At metal-metal tests, specimens as a pin are fixed on a steel disc with a fixed load where the disc rotates at a constant speed. Tests are applied on M2 steel disc with 0.52 m/s sliding speed, under 5 kg load and at a total sliding distance of  6000 m. Before and after each wear test, the differences at specimens in terms of height (H) and weight (G) are measured with a sensitivity variance of 0.01 mm and 0.1 mg respectively at every 2000 m sliding distance. Steel specimens without any surface treatment have surface hardness values in the range of 170 and 210 HV. After the surface treatment (nitrocarburizing, hard chrome coating and electroless nickel coating) processes, these specimens surface hardness increased up to 800 HV. However, after the boronizing process, specimens surface hardness increased to the higher values up to 1110 - 1495 HV. The results of wear tests are analyzed according to the weight loss of the materials. The relative wear ratio (RWR) is defined as the ratio of the weight loss of a specimen to the weight loss of the reference material, which is defined as the most wear resistant specimen at the wear tests. The most wear resistant material was found as the boronized AISI 4140 steel specimen from the weight loss values. mFrom the results of the pin on disc tests, the specimens weight losses are calculated to identify the relative wear ratio values. Non-coated AISI 420 specimen had the weight loss of 0.0552 gr, hard chrome coated AISI 420 specimen had the weight loss  of 0.0056 gr, boronized AISI 4140 specimen had the weight loss  of 0.003 gr at 2.000 m sliding distance. From the comprarison of the RWR values of the studied steels, it is found that the boronized AISI 4140 steel is the highest wear resistance material. The RWR values show that the boronized AISI 4140 steel is 18.7 times better than hard chrome coated AISI 420 steel, and 184 times better than uncoated AISI 420 steel in terms of wear resistance. As the results of the wear tests, the boronized AISI 4140 steel is determined as the most wear resistant material in the studied steels and suitable to use as the arm mould material in the glass forming machines. Keywords: Boronizing, glass forming machines, arm mould

A Simple and Fast Method for Discrimination of Phage and Antibiotic Contaminants in Raw Milk By Using Raman Spectroscopy

Phage and antibiotic in raw milk poses significant risks for starter culture activity in fermented products. Therefore, rapid detection of phage and antibiotic contaminations in raw milk is a crucial process in dairy science. For this purpose, a preliminary novel method for detection of phage and antibiotic was developed by using Raman spectroscopy. Streptococcus thermophilus phages and ampicillin which are quite important elements in dairy industry were used as model. The phage and antibiotic samples were added to raw milk separately, and Raman measurements were carried out. The obtained spectra were processed with a chemometric method. In this study, it has been demonstrated that the presence of phage has a titer sufficient to stop the fermentation (10(7) pfu/ml), and antibiotic in a concentration which inhibits the growth of starter cultures (0.5 A mu g/ml) in raw milk could be discriminated through Raman spectroscopy with a short analysis time (30 min).Wo